ri,g1CI-11.VEG

FISHERIES RESEARCH BOARD OF CANADA

Translation Series No. 1370

Automatism and reflex in the activity of the respiratory centre in vertebrates.

By B.D. Kravchinskii

Original title: Avtomatizm i refleks v deyatel'nosti dykhatel'nogo tsentra u pozvonochnykh zhivotnykh.

From: Uspekhi Sovremennoi Biologii (Development in contemporary biology), 19 (1): 291-315, 1945.

Translated by the.Translation Bureau (NKD) Foreign Languages Division

Department of the Secretary of State of 'Canada

Fisheries Research Board of Canada Biological Station St. Andrews, N.B.

1970

67 pages typescript

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PUBLISH ER - EDITEUR PAGE NUMBERS IN ORIGINAL NUMÉROS DES PAGES DANS

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Academy of Sciences 291-315

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DACTYLOGRAPHIÉES X IX Moscow - Leningrad 1 1945 67

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AUTHOR - AUTEUR

B.D. Kravchinskii

TITLE IN ENGLISH - TITRE ANGLAIS

Automatism and Reflex in the Activity of the Respiratory Centre in Vertebrates

Title in foreign language (transliterate forein characters) Avtomatizm i refleks v deyatellnosti dykhatelinogo tsentra u pozvonochnykh zhivotnykh

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Uspekhi sovremennoi biologii

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Development in Contemporary Biology

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Source: Uspekhi sovremennoi biologii (Developments in Contemporary Biology) Vol. XIX, Issue l e 1945. Izdateltstvo akademii nauk Souza SSR (Publishing

MJ House of the Academy of Sciences of the USSR) Moscow - Leningrad.

u c7 n „

e:■Z ■ SURVEY AND GENERALLY THEORETICAL ARTICLES /291 t—

z c

0 c) a ›. Ée? OF THE RESPIRATORY CENTRE IN VERTEBRATES

0 7D ,b B.D. Kravchinskii (Leningrad)

ua The question of the nature of the activity of the 7'

respiratory centre has been the subject of live discussion for

almost two hundred years, from the time of Robert Whitt (1751).

Closely connected with this question is the solution to the

general question of the mechanism of the origin of the functional.

activity of the central nervous system. Two principally

different concepts in the explanation of the nature of the

activity of nerve centres including the respiratory centre -

the theory of automatism and the reflex theory opposed each

other and contended for the right of exclusive recognition.

According to the first theory, there lies at the basis of the

activity of the entire central nervous system an inherent

• •SOS,-200-10-31

AUTOMATISM AND REFLEX IN THE ACTIVITY

automatic rhythmic activity which Originates in the centres

without the influx of external nervous impulses and is - only

under the influence of impulses originating in the nerve

centres themselves.

According to the second theory, the rhythmic

activity of all nerve .centres, including the respiratory

centre, is exclusively reflex in nature and is -dependenton

nerve impulses coming from the periphery; in the absence of

afferent impulses the central nervous system remains inactive.

DOCTRINE OF . AUTOMATISM OF THE RESPIRATORY CENTRE

The concept of the automatic activity of nerve

centres concerns the most complex and Controversial questions

in physiology. In general practice, the term automation is

applied to an apparatus which acts by means of an inner

mechanism (automatos self-moving) j .and automatism and

automatic activity is applied to movement which is involuntary,

accomplished without the participation of the will or con-

sciousness. -

This concept was first used in biology in this

sense, by Descartes who claimed that animals are superbly

equipped and'efficiently acting automats. Descartes (1648),

who was.the first to formulate the doctrine of reflex,

described the .reflex activity of animals bind man as tei4;

automatic, opposing it to the voluntary activity in man which

is an expression of the soul or reason of man.

The introduction of the doctrine of automatic

movement into physiology is indisputably accredited to Johannes

Muller, one of the foùnders of the reflex concept in the XIX

century.

Muller saw automatic rhythmic respiratory movements .

as being caused by the stimulation of the respiratory centre

in the medulla oblongata by arterial blood, fhe question

which remained obscure for Muller, however, was how stimulation

of the medulla oblongata by arterial blood, which is a constant, .

is transformed into rhythmic impulses. He suggests that "in /292

the medulla oblongata there is an unknown cailse which directs

the constantly exerting neural onset alternately in one direction

or in another". "The constant stimulation of the medulla oblongata

by arterial blood is transformed by an unknown cause into a

periodic alternating discharge of neural onset along the in-

spiration and expiration neural pathways. One discharge is

always the cause of the emergence of an opposing, antagonistic

discharge".

According to the hematogenous theory of automatism,

first formulated by Muller, the automatic activity of nerve .

centres is caused by adequate stimuli which originate outside

of the centres but which reach them not by afferent neural

pathways as in the case of reflex activity but humorally, by

means of the blood, affecting the centres directly.

4

The theàretic monopoly of chemical central regulation

on automatism of the respiratory centre, until recently, was

one of the most stable situations in physiology. Supporting

this theory . were the classic and, it seemed, convincing exper-

iments of Fredericq (1890), the perfilsive experiments of

Winterstein (1911) and others. However, the discovery of

chemical receptors in the aortic and sinocarotid reflexogenic

zones compels us to reassess the experiments of Fredericq and

Winterstein. .

The basic question which was debated by the supporters

of the hematogenous theory of respiratory automatism, during

the course of decades, is the question of the nature of the

basic stimulant of the respiratory centre s the so-called

"respiratory hormone". The greatest successes in the physiology

of respiration were achieved in attempts to establish the

. nature of the "respiratory hormone". Carbon dioxide, oxygen,

a concentration of hydrogenous ions etc. contested the right

to be called the "respiratory hormone" in different periods

in the development of physiology.

In the centrogennic theory of respiration developed

by Gesel'(1925), the necessity of a special "respiratory

hoimone" ceaSes to exist. The chemical regulation of respiration

is looked upon by him as a function of physicochemical balance

in the cells of therespiratory centre.« Metabolism of the

respiratory centre is the basic factor in the regulation Of

5

the respiratory centret.s own activity and depends upon the

relation between the -following factors: . chemical composition

of blood, metabolic rate in the cells of the reàpiratory

centre, amount of blood supply and the buffer activity of

nerve tissue in the area of the respiratory centre.

However, the. extreme sensitivity of the respiratory

centre to changes in the pressure of carbon dioxide in alveolar

air and in blood.and also the fact of the pressure constancy

of carbon dioxide in alveolar air under certain conditions

during the course of many . days and months sTi)eak in favour of

the decisive role of carbon . dioxide in the regulation of

respiration. Hess (1931) cornes to the conclusion that "in the

mechanism of chemical regulation of respiration, carbon dioxide,

with its unusual capacity to pass through live membranes, is

an integral agent maintaining a contact between the body and

the respiratory centre".

For an explanation of the mechanism of the origin

of automatic rhythmic impulses in the respiration centre,

electrochemical hypotheSes have been suggested (Gesel) in

which the respiratory centre is compared to certain' models in

physics.

However, with the present level of knowledge about

the chemiçal dynamics of the nervous system, the chemical

theory of automatism., apparently as yet, can shed little light

on the problem of the mechanism of the genesis of automatic •

6

impulses in the central nervous system. With certainty,

it has only been established that the nerve cells of the ,

respiratory systen, during the discharge of impulses which /293

they send to the periphery, consume energy, since for their

activity they require an appropriate amount of oxygen. The

specialized function of the respiratory centre, which consists

in the discharging of impulses, is found to be closely depen-

dent on the concentration of hydrogenous ions in the centre

itself. Displacement of the acid-alkaline balance to the acid

side leads to an increase in the frequenCy of impulses and

displacement to the alkaline side, to a curtailment of impulses..

In this respect, the cells of the respiratory centre do not

differ from other nerve cells. However e they are unique in

their kind, being capable themselves of regulating their

alkaline-acid balance since their activity gives rise to

opposing changes in the alkaline-acid balance in the blood by

means of regulating the respiratory movements and, conse-

quently, regulating the removal of carbon dioxide. The respi-

ratory centre is frequently looked upon as a vigilant watchman,

constantly protecting the alkaline-acid balance in the entire

organism. However, it is more accurate to regard this function

as a secondary consequence of the capacity of the respiratory

centre to react to unfavourable changes in its inner environ-

ment and to restore in it the initial chemical balance inde-

pendent of the overall state of the organism. In restoring the

7

the alkaline-acid balance in Its own inner environment, the

respiratory centre most often contributes also to the restoration

of the alkaline-acid balance in the entire body. .

With his suggestion of the presence of an unknown

cause in the medulla oblongata which converts the constantly

acting stimulation of the blood into periodic discharges of the

respiratory centre, Johannes Muller laid the basis for a number

of theories of automatism of nerve centres based on the inner

properties of the centres themselves.

Luciani saw the cause ôf automatic discharges, which

originate in the nerve centres, in the fluctuations in sensitivity

of these centres associated with the fluctuations in trophic

processes. This point of view finds its furthest development

in the works of a number of authors in connection with the doctrine

of refractivity.

Hess (1931) formulated a theory of automatism of the

respiratory centre according to which a constantly acting stimulant,

like the pressure of carbon dioxide or a concentration of hydro- •

,genous ions, is capable of transforming itself into the alternating

rhythm of the respiratory centre owing to the phenomenon of

refractivity. Stimulation of the inspiration centre arising

under the influence of the constant pressure of carbon dioxide

changes, owing to the onset of the refractive phase, into in-

hibition of the inspiration centre in order to go over again

into a state of stimülation at the end of the refractive phase.

8

A number of contemporary researchers such as Graham ty

Brown'(1,915), - Brucke (1929) gnd others believe that the basic

form.of activity of the central nervous system is not the reflex

but an automatically arising rhythmic activity. According to

Brownl "reflex is a distorted form of the basic automatic

activity". Reflex is looked upon by them "as the latest phenomenon

arising as a result.of the play of the afferent sensory mechanism

which develops later".

"Primary rhythm" or "organic rhythm" of the central

nervous system is expressed in very widely spaced discharges

(5 - 6 per minute). Frequent innervated rhythms, in the opinion .

of Brucke, do not correspond to the "organic rhythm" àf the

centres but represent its modification under the influence of

the reflex proprioceptive impulses. The removal of these impulses

make the innervated rhythm again widely spaced, restoring the

"organic rhythm" of the centres. As evidence of the centrogenic /294 origin of Innervated rhythm, the authors repeatedly fall back

of upon the cooling and warming.the brain which leads to a corr-

esponding change in innervated rhythm.

Other evidence' of the central origin of innervated

rhythm is the preservation of this rhythm during deep narcosis,

when all other reflex actions have been turned off , Graham

Brown (1915) cites data on the presence of rhythmic ambulatory

movements in a spinal animal in a state of deep narcosis.

A third piece of evidence of the central origin

of innervated rhythm is the preservation of this rhythm after

severing the sensory pathways. Thus, phasic strychnine tetanus

is preserved even after severance of the posterior radicles

(Buchanan,. Burdon and Sanderson, 1902). Uraham Brown (1915)

informs us tHat by freshly severing the spinal cord at the level

of the last thoracic segment one may briefly observe ambulatory

.movements even in the case where the posterior extremities are

deprived of afferent innervation. Brown cites still another

fact - that the rhythm of alternation is preserved after an

extremity which produces a given rhythmic movement (scratching,

walking) has been entirely deprived of afferent innervation.

On the basis of these data, Brown considers walking to be the

• result of the same automatic rhythmic activity of the central

nervous system as is breathing. Further, he asserts that rhythmic

activity, widespread in the nervous system, in all cases is the

result of the basic rhythm of the centres which is modified by

the stratification of different reflex influences.

However, the preservation of innervated rhythm during

deep narFosis cannot be used as evidence against the reflex

origin of innervated rhythm since even deep narcosis can act

differently on different receptor systems •, turning off some

of them while preserving the efficiency of others. And, in

exactly the same manner, the possibility of changes in the

innervated rhythm by means of direct cooling or warming of the

10

brain by no means serveeas evidence against the reflex origin

of this innervated rhythm. The facts cited by Brown may be

explained entirely satisfactorily by the phenomena of successive

induction, described by Sherrington, which can manifest itself

both in a state of deep narcosis and after a fresh severing of

the spinal cord, acting as a strong stimulus.

In his textbook on the physiology of the nervous

system (1866), Sechenov, in enumerating the properties of nerve

centres, refers to their capacity for automatic activity.

However, he also mentions that "the latter property is assumed

only because it is necessary for cases where, hitherto, no

external point for the origin of the nerve act has been found".

Thus, Sechenov considers the acknowledgment of automatism of

the respiratory centre to be forced and to be an exception in

the overall concept of reactions of the animal organism.

In exactly the same manner, Bethe (1906), in con-

sidering the nature of nerve centres, asserts that "not one

nervous system, as far as we know up to the present time,

works on its own; it requires a constant external stimulus

which may have its basis within the body of the animai".

Speaking out still more definitely on this question

is Starling (1930) in his textbook on the physiology of man:

"It is possible that neurons possess a certain automaticity,

i.e. a capacity for exciting neural processes under the influence

of changes in the surrounding fluids. However, this automaticity

11

L2_22 is not a prominent feature of the nervous system, which was

differentiated as a purely reactive mechanism on the afferent

Impulses arising under the influence of material changes.

occurring uninterruptedly in the surrounding environment".

2. REFLEX CONCEPT OF ACTIVITY OF THE RESPIRATORY CENTRE

The-intensive working out of the problem of reflex

action of an organism, beginning with Marshall Hall (1833) and

Johannes Muller (1833) to the present time, led to cardinal

discoveries in the area of the physiology of the nervous system:

The reflex nature of almost all reactions of an organism was

established, conducting pathways were studied and the location

of many reflex centres in the CNS was determined. Achievements

in the development of the reflex' concept led to the view that

the reflex is the basic form of neural activity. Under the

pressure of experimental facts, one position after another

found itself defeated, by the reflex concept. .Debatable, in

due time, was the nature of voluntary muscular activity,

muscle tonus, automatic rhythmic activity of extremities

(Walking and running) and activity of vasomotor and respiratory

centres. Presently, the greater part of these questions have been

resolved in favour of the reflex concept. The nature of the

activity of the respiratory centre remains an open question.

One of the first authors of .the reflex concept was

Robert Whitt, an Edinburg doctor. At the dawn of the conception

12

of the reflex theory, he gave in his work Vital and Other

Involuntary Movements in an Animal a completely finished original

theory of the "self-regulation" of breathing, which was later

independently developed by Hering and Breuer . (l868). Whitt,

looked upon breathing as a reflex act, the rhythm of which

springs from'Stimulations originating in the act itself. He

considered expiration to be a passive process in which the

stimulations originate which cause inspiration; but inspiration

removes the conditions which cause inspiration and consequently

the passive process of expiration occurs again. Of particular

interest, according to Whitt, is the fact that the place of

origin of the respiratory reflexes is not only sensory nerve

endings in the pulmonary epithelium, as was later suggested

by Hering and Breuer, but mainly the pulmonary vessels, the

flow of blood through which shouid be regarded l according to

• Whitt, "asthe cause giving rise to regulating and retaining

respiratory movements". Thus, Whitt not only anticipated

the doctrine of "self-regulating breathing" of Hering and

Breuer by more than a hundred years, but he astutely anticipated

the doctrine of ,our own time of respiratory reflexes from

vascular reflexogennic zones.

Subsequently, the ideas expressed by Robert oihitt

were basically forgotten and it is impossible to find anything

about them in later literature.

Traube (1847) advanced the theory Of reflex regulatiOn

13

of respiration by means of the stimulation of alveolar air of

the sensory endings of the vagus nerve by carbon dioxide. This

theory was refuted-by Geppert and Zuntz (1880) and Haldane (1922)

and, in a particularly convincing way, by Zh. F. heimans and

K. Heimans* (1927) who, by means of perfusion of an "isolated"

head and "isôlated" lungs connected to each another only by

vagus nerves, showed.that the ventilation of "isolated" lungs

by air which is rich in carbon dioxide and poor in oxygen does

not stimulate reflexly the respiratory centre of the "isolated"

• head.,

In the question of the reflex regulation of,the

respiratory centre, hering and Breuer (1868) returned to the

original point of view of Robert -vihitt. ihey explained the jr.(? 1

-activity of the respiratory centre by antagonistic reflexes

aroused by means of the vagus nerves by the expansion and

collapse of the lungs in the act of inspiration and expiration.

Christiansen and Haldane (1914) discovered the

respiratory reflexes of Hering and nreuer in man. On this

basis, Haldane subsequently concluded that "the respiratory

centre in man does not function independently of pulmonary

movements, that inspiration and expiration impulses of the

respiratory centre are synchronic with inspiration and expiration-

* Direct transliteration from Russian. .Items 5, 61, 64 and 65 in the bibliography may be referred to for further possible clarification as to spellings. - Translator.

14.

movements of the lungs, as though

the respiratory centre were connected only with the lungs".

The data:of Hering and Breuer found corroboration

in the latest eleCtrophysical works of Adrian (1933).

Registering the flows of activity of isolated fibres of the

vagus nerve of a female cat which carry afferent impulses from

the lungs, Adrian corroborated the results of Khed* and also

presented new data which clarified the role of the reflexes of

Hering and Breuer in.the regulation of respiration. He established.

that inspiration impulses occur every time with inspiration, but

expiration impulses occur only with forced expiration. With

lengthy expansion of the lungs,while the breath is held after

inspiration, the inspiration impulses all the while continue to

proceed indicating the poor adaptation of the receptors to

stimulus, similar to the proprioceptors of the skeletal muscles.

According to Adrian, there are two types of receptors

located in the most 'expansible parts of the lungs - in the

alveolar ducts: inhibUory inspiration and stimulatory expiration.

The receptors are practically insensitive to changes in the

composition of air and are not stimulated by air current.

During normal breathing, only the inhibitory inspiratory receptors

function which are responsible for the dering-Breuer reflexes.

* Direct transliteration from the Russian. A possible English rendering is Head - Translator.

1 5

Stimulatory expiratory receptors rarely participate in the

normal regulation of breathing. fhey are stimulated only in

pathological conditions (with exudates, atelectasis and pneu-

mothorax). Inhibitory inspiratory receptors have a different

sensitivity to expansion. The degree of inhibition of the

respiratory centre progressively increases during inspiration

and depends on the state of expansion of the lungs, consequently,

on the original position of the thorax which, in turn, depends

on the tonus of the inspiratory and expiratory musculature.

It was Hering and Breuer (1868) who 'established that

the vagus nerves not only reflexly regulate the rhythm and

amplitude of respiration but also maintain reflexly the tonus

of respiratory musculature. By means of. registering the currents

of activity of diaphramic and intercostal nerves, vîachhoIder

and MacKin1ey (1929) succeeded in showing that even durin

expiration the respiratory muscles', particularly the diaphram,

are tonically reduced.

Numerous investigators . (Boothby and Shamoff, 1915;

Coombs and Pike, 1918; Fleisch e 1933 and others) showed that the

proprioceptors of the respiratory apparatus, stimulated both

during respiratory oscillations of the thorax and static

inspiratory and expiratory positions of the thorax, show reflex

influence on the respiratory centre. Particularly interesting

are the electrophysiological data with registrations of currents

of activity of a peripheral section of the diaphragm nerve

16

(Gasser and Newcomer, 1921) and intercostal nerves (Scott, Gault

and Kennedy, 1922), synchronous with the respiratory movements

of the thorax.

These facts testify.to the presence of constant

afferent impulsesjoing from the proprioceptors of the respiratory

apparatus to the respiratory centre. Data in . the literature

indicate with certainty that the activity of the respiratory

centre is regulated by these proprioceptor reflexes. However,

these data do resolve th è question of the role of these J297

reflexes in the mechanism Of the origin of the activity of the

respiratory centre.

In the literature known to us, there are no direct

data. on the presence of constant tonic impulses from the tri-

geminal nerve to the respiratory centre analogous to the vagal

impulses of Hering and Breuer. Difficult accessibility for •

surgical intervention of the Gasserov node and the sensory

radilce of the trigeminal nurve possibly prevented the setting

up of such experiments. • -

There are numerous data on the disturbances of

respiration caused reflexly by influence on the olfactory,

visual and auditory organs; however, there is no basis for

proclaiming constant tonic influences of the olfactory,.auditory,

vestibular and visual nerves on the respiratory centres. In

any case severance of these nerves did not.reveal these

tonic influences.

1 7

Respiratory reflexes of vagal, thoracic and dia- .

phragmatic origin proceed directly from the reflexogennic zones

of the respiratory apparatus itself. Of no less' basic importance

are the relatively recently discovered respiratory reflexes

proceeding from the reflexogennic zones situated in the organs

of circulatidn,. namely, from the aortic and sinocarotid pres-

soceptive zones and also from other areas of the vascular system:

the area of the vena cava, meningeal vessels, vessels of the .

spleen and liver etc.

At the present time, there is conclusive proof of the

presence, both in the sinocarotid and aortic areas, of two separate

reflexogennic receptor zones which are sensitive to changes in

endo-vascular pressure and changes in the chemical composition

of the blood(Heymans, 1929; Schmidt, 1932;.Burnthale, 1938;

Comroe, 1939 and others).

The presence of cherrj_cal receptogennic zones in the

aortic and sinocarotid areas which participate in the regulation

of respiration compels us to re-examine the question of the

mechanism of the origin of the activity of the respiratory centre

since a chemical stimulus may influence the respiratory centre

not by direct action on the respiratory centry but reflexly,

through chemoreceptors of the vascular reflexogennic zones.

The question of the physiological role of the aortic

and sinocarotid reflexes in the regulation of- respiration •

and their significance in comparison with the central meéhanism

18

of respiration is at the prescrit time a subject of intense

discussion.

Some authors, including Heimans and his school,

pointing to the high sensitivity of the carotid sinus to

chemical stimuli insist on the primary role of the sinocarotid

mechanism in the regulation of respiration. Heimans comes to the

conclusion that the degree of blood supply' and metabolism in

the cells of the respiratory centre is a decisive factor in

the regulation of its activity only in unusual circumstances

which are not of physiological interest.

The simultaneous severance of both the aortic and

sinocarotid nerves in the experiments of Bacq, Brouha and

Heymans (1934) cause .dispnea, equally with prolonged high blood

pressure. This fact is cited by Heimans as evidence of the

presence of tonic inhibitory impulses goini; to the respiratory •

centre via the aortic and sinocarotid nerves •

Author authors (Schmidt, 1932, iiright, 1930, Schmidt

and Comroe, 1937) maintain that the available facts do not

provide a basis for proclaiming a role for the sinocarotid

mechanism, which is more an accessory rather than a necessary ,

constituent part of the normal 'regulation of respiration

* This is the transliterated form, but it would appear from the reference in the following paragraph that Heymans is the English spelling. - Translator.

19

This mechanism begins to. function only in extreme critical i298

conditions: high'content of carbon dioxide, anoxemia and the

action of poison. Under usual conditions, the regulation of

respiration is accomplished by the direct action of chemical

stimuli, mainlY carbon dioxide, on the respiratory centre.

According to C. Schmidt (1938), reflexes with presso-

and chemoreceptors of the aortic and sinocarotid reflexogennic

zones do not play a practical role in the regulation of res-

piration in mammals. In chronic aseptically conducted experiments

of denervation of the sinuses and aorta, respiration, according

to Schmidt, in no way differs from the normal. The hyperpnea

which was observed in the first days quickly passes, whereas,

Tachycardia and high blood pressure remain.constant. This

perMits Schmidt to conclude that tonic.inhibition by the aortic

and sinocarotid nerves of the respiratory centre is not necessarY • for the maintenance of normal activity to the same degree as

for the cardiac vagal centre and the vasomatorial centre. •

According to Schmidt, the chemoreceptors of vascular reflexo .-

gennic zones are specialized for reaction to a drop in oxidizing

proceSses in themselves by the emergence of afferent impulses

going to the respiratory centre. They are less sensitive than

the cells of the respiratory centre to physiological changes in

carbon dioxide tension and concentration of hydrogenous ions.

However, chemoreceptors are more resistant to unfavourable

conditions. They are the ultimum moriens of the.regulating

20

system of respiration, a mechanism which is relatively insen-

sitive and cruder, being included in the action during particu-

larly difficult conditions for purposes of maintaining the

activity of the respiratory centre. The dispute between the

schools of Heimans and C. Schmidt becomes basically a question

of the mechanism of the. origin of activity of the respiratory

centre. Whereas heimans completely adheres to the point of view

of the decisive role of the reflex chemoreceptor apparatus in

regulating the activity of the respiratory centre, Schmidt

regards as decisive (for mammals ) the sensitivity of the

respiratory centre itself to'carbon dioxide and assigns to

reflex chemoreseptor apparatus only the role of a reserve

mechanism which enters into action only under extreme:cir-

cumstances. fqevertheless, in considerinL the question of the

nature of the activity of the respiratory centre, C. Schmidt

(l938) arrives at the following conclusion:

"the possibility that we actually are dealinb with a mechanism

which is basically a reflex mechanism seems to be more certain

than it was ten years ago".

ATTEMPTS AT COMPLETE DEAFFEàENTATION OF THE RESPlitATORY

CENTRE

For a conclusive solution to the question on the true

nature of the rhythmic activity of the respiratory centre attempts

at a more or leàs complete deafferentation of the respiratory

21

centre have been made repeatedly, i.e. its isolation from all

peripheral afferent impulses.

Rosenthal (1862) was one of the first,to carry out

a significant deafferentation Of the respiratory centre on

rabbits: despite severance of the spinal cord at the level .

of the 7th cervical segment and the brain stem in the area of

the lamina quadrigemina as well as severance of all posterior

radicles in the cervical part of the spinal cord and bilateral

vagotony, the rabbit continued to breath rhythmically.

Langendorff (1887) isolated the respiratory centre

in a frog by means of the removal of the cerebral hemispheres -

and the midbrain, destruction of the spinal cord and extripation

of the heart and lungs; nevertheless, the nostrils and vocal

cords continued to produce rhythmic respiratory movements for

a certain time.

Marckwald (1887) came forward as a defender of the /299'

reflex theory of respiration: he severed the medulla oblongata

at the level of -the striae acusticae in a rabbit; breathing

continued Without particular changes. however, when he added -

bilateral vagotony to this operation, the breathing changed

abruptly: lengthy apasmodic inspiratory arrests of 1 - 2

minutes set in alternating with'active or passive expirations.

A subsequent severance of the spinal cord at the leval of the

last cervical vertebra and a bilateral severance of the cervical

and brachial plexus as well as both glossopharyngeal nerves

22

did not introduce any changes in the breathing picture which

was obtained earlier. Màrckwald came to the conclusion that

normal rhythmic respiration is a reflex act which is carried

out by means of the vagus nerves. During the exclusion of the

vagus nerves, the "upper cerebral pathways" replace them.

i.e., the nerves of the higher sensory organs, trigeminal

nerves and others. But with the exclusion of both impulses,

the automatic activity of the respiratory centre is expressed '

only in arrhythmic respiratory spasms.

However, the conclusions of Màrckwald underwent

severe attack from Franck and Langendorff (1888). They insist

that the isolated respiratory centre of the rabbit and female

cat iS not only capable of developing automatic actiVity but

that it also maintains almost normal rhythmic activity. They

look upon the respiratory spasms as a side effect of brain

lesion. 2hey explain their absence in the presence of the vagus

nerves by the regulating role of these nerves.

In subsequent years, Marchwalk (1890) as well as

Ascher and Luscher (1899) corroborated the initial observations

of Marckwald and showed that the functional exclusion df the

cerebral hemispheres, midbrain and lamina quadrigemina by

means of the introduction of congealing substances in the

vesels of the brain does not cause any disôrder in the breathing

of the rabbit,*. but a subsequent severance or the vagus nerves

causes the characteristic Marckwaldian changes in breathing,

expressed by lengthened spasmodic inspirations.

Studiçs'Onthe dsOlation of the respiratory centre

fi'OM -affeent influenCes.were renewed at the beginning of the

XX century. :For this Ptirpose,Étewart and Pike (1907) used

tempOrarY adut“neMia.of.the cerebrum and the cervical part

of the Spinal cp .i*d, which theY caused by a teMporary pressing

of the ateriésHdoing toYthe head. They observed that after

the restoration of normal circulation, by a certain time,

there arose spontanebus respiratory rnovementS, whereas, reflex

- excitability of the respiratory centre towards an artificial

stimulation of different senSory nerves (sciatic and vagus

nerves) i‘fas . .still not restored. The. respiratory rhythm observed

was similar to that . which appeared after a bilateral vagotomy.

The rpspiratory rhythm (4 times per minute) was. constant not

onlyin different individuals . of one and the same species of

animal bût eVen in different species of . animals (dog, cat,i:4

rabbit). Stewart and Pike call this respiratory rhythm "basic"

regarding it as a direct expression of the automatic activity

of the respiratory centre.

An attempt at the most complete isolation of the

respiratory centre was made by Foa (1911) who repeated the

experiments of Rozenthal (1862) and marckwald (1887). He

severed the vagus, sympathetic cervical and diaphragmatic

* Throughout the translation the cat is female. - Translator.

24

nerves on both sides and all posterior radicles of the

cervical part of the spinal cord. After this, he severed the

spinal cord at the boundary of the cervical and thoracic part

and also severed the stem of the brain at the upper boundary

of the medulla oblongata. After such a complex operation, the

animals required prolonged artificial respiration to sustain

life. After this, they could breathe spontaneously for several /300

hours. he respiratory movements observed were noted for their

asthenic and ataxic nature. Nevertheless, the results obtained

made it possible for Foa to conclude that the respiratory centre

isolated from all afferent impulses, is capable of automatic

activity.

The experiments of Foa were repeated by G.F. Heymans

and G. Haymans (1927) on annisolated" head of a dog included in

• • the carotid-jugular circulation of another dos. From this

isolated head, the author 'removed .the cerebrum above the

'medulla oblongata, severed the glossopharyngeal, lingual and

trigeminal nerves. 'Nevertheless, it could be established that

the breathing throat of a head isolated in this manner con-

tinued to produce respiratory movements.

The most recent attempt at incomplete deafferentation

of the respiratory centre was carried out by Fleisch and Tripod

(1938) who studied the afferent pathways and mechanism of the

origin of eompensating and.adapting diaphragmatic'reflexes of

Fleisch (1933). :.1.1he authors severed, in a'cU5, the 3rd to 7th

posterior radicles, inclusive, in the cervical part of the spinal

cord, the cervical sympathetic and vagus nerves on both sides.

2 5

Despite the severing the diaphragmatic reflexes of Fleisch

continued to take place. The authors express a number of

hypotheses (of little probability at the time) on the afferent

pathways of these reflexes. It should be pointed out that in

the experiments of Fleisch and Tripod which were described the

1st and 2nd posterior cervical radicles remained unsevered.

For this reason; the state of the diaphragm and the thorax is

reflected on the conditions of inflow and outflow in the cardiac

cavities which may be reflected reflexly respiration through the

sinocarotid apparatus which remained excluded.

Defenders of the theory of automatism of the respiratory

centre regard the most decisive evidence of automatism to be the

experiments of Winterstein (1911) with registration of currents

of action of the central ending of the severed diaphragmatic

nerve in a curarized rabbit the life of which was maintained

according to the method of Melitser* and Auer* by the intro-

duction of compressed air into the trachea (up to 15 - 20 of

mercuric column). The presenc e . of currents of action in the

diaphragmatic nerve, despite the absence of respiratory move-

ments made it possible for the author to draw a conclusion on

the automatic activity of the respiratory centre. The experiments

of Winterstein.were repeated and corroborated by Adrian (1933),

and Adrian, Bronk and Phillips (1932), who registered the currents

of action of the diaphragmatic nerve of a curarized animal with

the aid of theoscillograph of Mettyus*.

* Direct transliterations from the Russian. - Translator.

26

However, it Should be noted that curare, which

paralyses the endings of the motor nerves of respiratory mus-

culature, in no way excludes afferent impulses doing from the

respiratory apparatus. Maintenance of the thorax in a pro-

longed inspiratory position and the expansionof the lungs

during the introduction of compressed .air into the trachea

according to the method of Melltser and Auer could serve as a

constant source of afferent impulses of a vagal, thoracic and

diaphragmatic nature. The pulmonary receptors of expansion,

as the experiments of Adrian (1933) showed, similar to the

proprioceptors of the skeletal musculature, adapt poorly and

during prolonged•expansion of the lungs the inspiratory afferent

impulses continue to advànce along . the vagus nerve. With this

*information, the conclusion of the. experiments of vinterstein,

Adrian, Bronk and Phillips cited above become highly questionable.

The defenders of the theory of automatism of the

respiratory centre particularly emphasize the importance of the

experiments of Adrian and Buytendijk (1931), who registered the

currents of action .of the respiratory centre in an isolated /301

brain stem of a goldfish extracted from the body of the animal.

The periods of oscillation of the potential almost coincides

with the normal rhythm of respiration and, in the opinion of

the authors, depends.on the rhythmic activity of the respiratory

centre.

• ■

27

As early as 1_882, Sechenov, with a more primitive

method, with the help of a compass, detected in the medulla

oblongata, which was extracted .from the skull and remained in

contact with the , cord which was also extracted from its

canal, spontaneous rhythmic oscillations of galvanic current,

which he associated with the spontaneous occurrence of dis,

charges in the medulla oblongatal "Spontaneous oscillation

of the current are essentially the expressors of stimulating

impulses originating in the medulla oblongata which is separated

from the middle part of the cerebrum". however, Sechenov does

not associate the spontaneous rhythmic oscillations of the

current with the automatic impulses of the respiratory centre

but regards them as "expressors of movement impulses originating

in the medulla:oblongata upon.itL 17eparation from the middle the

parts ofAcerebrum and producing forced movements". The emergence -

of rhythmic oscillations of the current in the medulla oblongata

is explained by Sechenov by stimulation from the wounded

surfaces of the brain and also by the "deforMation of the upper

half of the brain associated with its atrophy".

These observations by Sechenov should also be

completely relevant to the experiments of Adrian and Buytendijk:

fresh severances of the brain, in their experiments, could

undoubtedly serve as a .continuous source of sensory impulses to

the•respiratory centre whose activity they maintain.

2 8

The possibility of a spontaneous formation of

rhythmic impulses in an isolated respiratory centre is by no

means excluded by contemporary authors. 2he latest

electrophysiology data by C. Schmidt (1938) support the ability

of the cells of the motor nerves to form rhythmic impulses.

In exactly the same manner, isolated neurons of the sympathetic

nervous system . manifested rhythmic volleys of impulses; during

the registration of currents of action of cardioaccelerator and

vasoconstrictive fibres, these volleys of impulses frequently

have the same rhythm as breathing. However, the question is to

what extent the capacity of isolated neurons for automatic

activity can be used during the normal functioning - of the

nervous system.

In summing up the attempts at deafferentation of

the respiratory centre, Gustav Bayer (1925) justifiably points

to the impossibility of the complete isolation of the respiratory

centre from the afferent impulses and .to the fact that the

operative methods which should lead to isolation and the exclusion

of stimulations are themselves a'source of numerous impulses

going to the respiratory centre from all the Severed nerves and

conductor pathways.

The method of deafferentation, so much the more of

complete deafferentation, cannot provide the answer to the true

nature of the açtivity of the respiratory centre since deaf-

ferentation itself to a certain degree, leads to the destruction

29

of the dynamic whole which is called the centre. The deafferented

respiratory centre is no longer the same respiratory centre

it was in the intact animal: it becomes inert and insensitive

to humoral and reflex stimuli. The conclusions which we

obtain by deafferentation cannot be applied to the respiratory

centre functioning in an intact animal in close interaction

with all of the numerous afferent systems of the organism.

They only give evidence of a respiratory centre of profoundly .

defective deafferented animal. Therefore, the presence of

absence of respiratory movements after complete or partial

deafferentation does not give us the right to make a final /302

opinion on the true nature of the activity of the respiratory

centre and on the presence or absence of automatism in the

nerve centres in general.

L. AFFERENT SYSTEM - STIMULATORS OF THE FUNCTIONAL

ACTIVITY OF THE CENTRAL NERVOUS SYSTEM

Automatism and the reflex principle in the activity

of the respiratory system have not until recently been opposed

as mutually exclusive mechanisms. Meanwhile, in actUality,they

turn out to be closely interwoven and interrelated. The humoral

conditions of the environment show their influence on the excit-

ibility of the nerve centres to reflex stimulations, but the

afferent impulsés in turn condition the excitibility of the

nerve centres to humoral stimulations and, in addition,

30

maintain their capacity for automatic activity. As the results

of numerous investigations show, all sensory organs without

exception, in addition to their reflex phasic function, fulfill

the role of stimulators of tonus of the central nervous system.

For certain affernet systems, this is the primary function.

In his textbook on comparative physiology, Buddenbrock (1928)

cites the most interesting facts on the stimulation of the

4ctivity of the central . nervous system: he describes specialized

mechanoreceptors, the main purpose of which is not in causing

certain reflex reaction but in the regulating influence which

they have on the normal functioning of the motor apparatus.

They are first encountered in coelenterata (in jellyfish) in

the form of sensory bulbs containing an otolithic apparatus

in the distal end. Their function according to Uexkull (1904)

is very unique: automatic rhythmic contractions of the umbrella

of jellyfish are found to be in direct relationship to the

stimulation of otoliths during uninterrupted pendulum-like

oscillations .of the sensory bulbs caLsed by the constant move-

ment of water. With . the removal of all bulbs exCept one, the

contractions of the umbrella continue, but, when a thin stick

interferes with . the pendulum-like oscillations of this last

bulb, the rhythmic contractions of the umbrella of the jelly-

fish quickly 'cease.

In insects, we encounter similar . stimulator organs,

for example balancers in flies. Morphologically, they are

31

transformed into posterior wings. During flight, the balancers

move in very fast rhythm synchronically with the movements of

the wings. These movements stimulate the sensomi- cells at the

base of the clava of the balancer, toning the flying musculature.

The cementing or extraction of the balancers sharply decrease

the motor capacity of the wings. A fly devoid of balancers can

only produce unskillful leaps. In many species of flies, the

feet are so weak after the removal of the balancers that a fly

which is motionless cannot hold itself up in a normal way. In

some species of.flies, the sensory endini;s of the feet also

serve as stimulator crgans. ';vith the amputation of all six feet

a fly can still fly. But after the additional remover of the

balancers, a fly not only loses the capacity for flight but also

all mobility disappears in the wings which react only with move-

ments of insignificant amplitude to the strongest stimuli.

Nigh moths are an interesting example; awakening after diurnal

sleep, they are not capable of flying at first. Only after

they buzz for a long time without rising into the air do they

recover their flying ability. l'his buzzing before flight

apparently serves, with the aid of proprioceptive stimulations,.

to supply new toning up stimulating impulses in the nervous

system which has been weakened by diurnal•sleep. .

Particularly interesting are the respiratory /303 i

movements of thelarVa of the dragonfly which consist of

rhythmic movements'of the abdomen. The ganglion of the

3 2

posterior segment is regarded as the centre of these res-

piratory movements which emerge reflexly as a consequence of

the stimulation of the receptors situated in the' anal valves

of the appendages.of the posterior segment (Matula, 1917).

The .organs which stimulate the tonus of this respiratory

reflex arc are the sensory formations which are situated

in the front pair of limbs (in the tarsus). Severance of

the ventral chain behind the thoracic ganglion and also the

removal of the anterior limbs lead to an abrupt slowing down

of respiratory movements.

The mechanoreceptors in the metatarsal surfaces of

the feet of insects as well as the numerous sense organs of

unknown function, especially the chcirdotonal organs found in

the legs, wings, trunk and antennae of insects, possess the

distinct function of stimulating organs.

Muscle tone, being both in invertebrates and verte-

brates a necessary condition for maintaining a fixed position,

and for moving, is the result of a continuous flow of impulses

along the afferent nerves.

According to Buddenbrok e muscle tone declines

greatly when an animal is brought to the state when stimulations

of the external environment are . reduced to à minimum. Thus,

Sipunculus e lying for a long time in its sandy tubule, covered

with mucus, is completely atonic and unexCitable. But when it

is taken from the tubé and mechanically stimulated, muscle tone

is again reStored.

3 ,3

Maintenance of body position and organs of animals

depends on the tonic contraction of certain groups of muscles,

which is accomplished due to the presence of speCial adjusting

reflexes evoked by the stimulation of visual dnd vestibular

apparatuses and Proprioceptors and exteroceptors of the motor

apparatus. AIL sensory organs, particularly visual and

vestibular apparatuses, may be regarded with full justification

as stimulator organs. Very interesting in this cnnnection are

the results of the observations of Galkin (193j) and Abuladze

(1936) on dogs with three distant . receptors (olfactory,

auditory and visual) destroyed. After such an operation,

the dogs sleep for twenty-four hOurs and awaken only to perform

the natural necessities.

In considering these facts, Academician I.P. Pavlov

(1935) cites an old fact by Shtryumpell*:. he had a patient whose

sense organs were injured, having only two outlets to the outer

world: one eye and one 'ear. Covering these openings with a

hand, he fell asleep in a fatal way. In connection with these

facts, it is relevant to recall the statement by Starling when

he was considering the problem of the autômatism of the central

nervous system, "with the absenée of afferent impulses the

entire nervous system would be inactive".

Stimulation of the most diverse exteroceptive systems

causes changes in the functional state of the central nervous

system.

* Direct transliteration from Russian. - Translator

34

Very interesting from this point of view are the data

of I.M. Sechenov which date back to 1903 on increased.muscular

efficiency under the influence of the stimulation of the sensory .

nerveS. These data served as the beginning of an experimental /304

study of phenomena of increase in the functional capacity of

muscles and sensory organs, under the influence of accessory

stimuli and were the bas,of a study of sensitization of

the sensory organs.

The role of exteroceptors in tonus of the central

nervous system is particularly clearly outlined during a

study of the evolution of the functions of the skeletal muscul-

ature In the ontogenesis of mammals which are born blind.

Koshtoyants and Ryabinovskaya (1935) note that by

the time the eyes of the new born animals are open, in the

period between the 7th and llth day of postnatal development,

the speed of muscle contraction is spasmodically shortened by.

half and the quantity of phàsphagen in the muscle increases.

On the basis of his observations in the study on

the change in chroMaxy in new born piglets, rabbits and mice,

Yu.A. Klass (1937) concludes that the opening of the eyes of

the animals coincides with a drastic shortening of chromaxy. •

In connection with the problem being considered by

us, the influence of the interoceptors of the respiratory appar-

atus on the tonus of the skeletal musculature is very interesting.

For the first tiMe, N.E. Vvedenskii (1879), in one of his early

35

works e carried out in the laboratory of I.M. Sechenov, pointed

to the existence of a connection between periodic general

movements and respiratory movements in the frog.

King, Blair and Garrey (1931), in a very -thorough

study, showed that tendon reflexes and the scratching: reflex

reveal a natural increase during the inspiration phase.

In a joint study with V.A • Muzykantov and h.L.

Mitropolitanskaya (1934), Kh.S. Koshtoyants showed that as a

result of the bilateral removal of the pulmonary sacs in axootls

there sets in very distinctly an atonic inert state in the

trunk musculature and a disturbance in the coordination move'

ment s.

A carp without a swim bladder behaves similar to

an axototl Without pulmonary sacs. It is well known that the

swim bladder of fish, being a derivative of the primary

intestinal tubule, is a formation which is genetically related

to the respiratory apparatus and the intestinal tract.

Having studied the nature of the tonus of the motor

musculature of the ascidian, Iordan (l935) showed the role in

this act by the branchial intestine which when filled with water

causes a distinct rise in tonus. Thus, the rhythmic act of

swallowing water by the ascidian is the source of rhythmic

processes of increasing and lowering.the tonus of the motor

musculature.

36

Numerous data in the literature convince us that the

hollow organs of respiration, circulation and digestion are a

source of continuous afferent interoceptive impulses which

tone the entire central nervous system, including the respira-

tory centre. Of the greatest interest in this respect is the

tonic influence of the pulmonary vagus nerves. According to

Kachkovskii (1899) and Cheshkov (1902), bilateral vagotomy

leads to ossification of the respiratory apparatus. The .

respiratory centre loses its mobility and its psychological and. '

reflex excitability fall,.. A correct relationship between the

frequency and depth of respiration and the strength and nature

of the stimulus is disrupted. During heat dyspnea, the breathing

of an animal which has undergone vagotomy is markedly. differ-

ent from the breathing of a normal animal and it easily acquires. ,

the nature of heavy dyspnea.

Baglioni (1911) speaks on the question of automism

of the respiratory centre, in this manner: when to this

characteristic (automatism) of the activity of the reSpiratory

centres we add the quite specific property wnich distinguishes the /305

respiratory centre from all other nerve centres, i.e., that their

normal activity does not depend on adequate peripheral impulses

going along afferent nerve fibres so that they can also be

active after they are isolated from all sensory nerves, then

the state of our knowledge does not provide a basis for such

an assumption",

57,

5. EVOLUTION OF REFLEX CONNECTIONS

OF THE RESPIRATORY CENTRE

IN VERTEBRATES

Until recently, in the study of comparative

physiology of respiration in vertebrates, the greatest

attention has been given to the examination of the evolution

of the mechaniSm of respiratory movements. fhe question of

the evolution of structure and functional interrelationships

of the respiratory centre and the entire innervation apparatus

of respiration has scarcely been touched. Pleanwhile, it is

these questions which require the greatest de;,;ree of comparative

physiological clarification. Thus, for example, the automatism

of the respiratory centre is regarded not as à certain stage

in the development of the animal world but as a basic . inherent

quality which is peculiar to the central nervous system of

every species of animal, regardless of its position on the

phylogenetic ladder of development. Cited as evidence for

either concept are fa ts from the physiology of respiration of

different species and classes of animals, including inverte-

brates, Mdthout consideration of data on the evolution of the

innervation apparatus of respiration. Meanwhile, "on the lower

rungs of evolution of animals we may encounter such regulator

mechanisms which in higher developed animals

• are

only found in a rudimentary state and manifest themselves only

in embryonic or early post-natal periods. In adult animals,

3 8

these regulator mechanisms may manifest themselves and prove to

be even crucial only under certain particular conditions"

(L.A. Orbeli). "By*means of a careful and thorough study of

the comparative physiology of the nervous system, we are able

within the specific activity of our nervons system to detect

traces of physiologically ancient forms àf activity and

to disclose those complexities which are conditioned by this

stratification of phenomena which date to different epochs"

(L.A. Orbeli) . . •

In comparative physiology of the nervous system,

there are two schemes of evolution of the innervation apparatus

of respiration. According to the first, which was developed

by Bethe (1903) in General Anatomy and Physiology of the

Nervous bystem, lower vertebrates (fish and amphibians)

possess an exclusively reflex apparatus of respiration which

is different from the automatism of the resPiratory centre

in higher vertebrates. Bethe explains his point of view on .

the reflex nature of respiration in lower vertebrates by the

absence of reactions of respiration to changes in the content

of gases in the outer environment. However, subsequent inves-

tigators showed the possibility of obtaining dyspnea in fish

and frogs in anaerobic conditions and in an atmosphere of

002 ' (Babak, 1907) and in the presence of cyanides, in frogs

(Karasik, 1928). On the basis of these investigations, the

forementioned authors came out in defence of the automatic

nature of respiration in lower vertebrates.

39

Discovery of the presence of special chemoreceptors

in vascular reflexogenic zones compelled us to critically

reconsider and subject to experimental verification the data

of the debate on the true nature of the activity of the res-

piratory centre both in lower and higher vertebrates.

The second scheme of evolution of the innervation

apparatus of respiration, developed by Lumsden (1923), concerns

the evolution of the structure of the respiratory centre.

According to Lumsden, fish and amphibians (frogs) only possess

one primitive respiratory centre "gasping" (sighs) which is

transitional between the centres of brachil and pulmonary /306

respiration and provides a trpe of respiration which consists

of separate deep sighs. Lumsden considered insensitivity to

carbon dioxide to be characteristic of this centre of "gasping".

The single stimulus of this centre is the insufficiency of

oxygen.

In reptiles (toroises), Lumsden assumes the

presence of three respiratory centres, the higher of these

• being the "apnoeic" centre which provides in reptiles a type

of respiration with long stoppages on inspiration. The

functioning in turn of the

active expiration establishes the characteristic respiration of

tortoises. The lower respiratory centre of "gasping" normally

does not even function in tortoises. The centres of respiration

of the tortoise: the apnoeic centre and centre of expiration

"apnoeic" centre and the centre of

1+0

are stimulated and regulated by thé active reaction of the

blood. In-higher vertebrates, in mammals, there appears an

additional fourth "pneumotaxic" respiratory cenGre which provides

a normal rhythm of respiration. Thus, in mammls, according

to Lumsden, there are four co-ordinative respiratory centres.

. centre of sighs ("gasping") in the area of the

writing pen*(in the location of the "nucleus of life"

of Flourens;

2) "apnoeic" centre in the area of the striae

acusticae;

3 ) centre of active expiration, located directly

below the area of the striae acusticae;

4) "pneumotaxic" centre, located in the upper

part of the Varolio bridge.

Lumsden considers the lower respiratory centres--

TTgasping", "apnoeic" and the centre of active expiration - in

mammals as rudimentary, put into action only after the higher

lying centres have been'cut off. The higher respiratory

centre - "pneumotaxic" - in mammals is regulated by means of

pulmonary vagus nerves which are stimulated by the expansion

of the lungs during inspiration.and their collapse during

• expiration. The appearance of the "pneumotaxic" respiratory

centre in mammals provides a rhythmic change in phases of

respiration.

* Literal rendition. - Translator.

41 _

Barcroft (1934) speaks out against the presence of

anatomically isolated respiratory centres; he allows only the

presence of the inspiratory and expiratory centres located in

the medulla oblongata at the level of the Flourens "nucleus of

life". According to Barcroft, the normal rhythm of respiration

is created by means of reflex inhibition of the activity of the

inspiratory and expiratory centres.

Basic reflex apparatuses, regulating the activity

.of the respiratory centre are the Vagal reflexes of Hering and

Breuer and the vascular sinocarotid and aortic reflexes.

On the basis of eMbryonic data, Koch (1931) and

Boyd (1937) came to the conclusion that the aortic and sino-

carotid zone in mammals should be considered as the vestiges of

the primitive branchial vascular system of the embryo and the .

sinus and aortic nerves are representatives of nerves which

innervate the branchial arches in the embryo: the sinocarotid

nerve - the third branchial archa and the aortic nerve - the

fourth and fifth branchial arches. In vertebrates which live

in water and have a branchial mechanism, the sensory nerves

of the branchial arches play, a role in the defence against the

penetration of poisons into the organism through the branchial

apparatus and ln the coordination of respiratory movements with .

the movement of the blood in the breathing surfaces of the

branchiae. But in mammals which breathe air, the aortic and

sinocarotid apparatus should be examined as a survival of

4e

primitive and older relationships having as its basic func Lion

the regulation of blood pressure and the activity of the heart.

On the basis of the embryological data of Koch and Boyd, the

discussion of the role of the branchial nerves in fish and

pressoceptor nerves in amphibians, reptiles and mammals is of /301

great interest.

For purposes of disclosing the picture of evolution

of the functional relations of the respir;?tory centre, we

conducted a comparative physiological investigation of the

reflex connections of the respiratory centre on different

stages of the phylogenetic development of vertebrates: fish,

amphibians, reptiles and mammals.

In analyzinL; the mechanism of the regulation of

respiration in fish, vie fixed our attention on the role of the

branchial nerves...It was established that severirw or the

vagus nerves beneath the skull in fish leads .to an irreversible

stoppage of breathing. A similar fact is noted also in the

work of American authors Klark .r.d Powers (1940). However, they .

did not subject this fact to further-analysis. Using the

method of sectioning rami of the vagus nerve on different levels

succeeded in proving that fibres, the exclusion of which causes

an irreversible cessation of breathing enter into the composition

of branchial nerves. In addition, in order to obtain the

described effect it is sufficient to sever only the fifth pair .

of the branchial 'nerves and only one prebranchial ramus of this

- pair.

43

A second fact which is no less important is the

general shock-like irreversible inhibition of the entire

central nervous system which develops after the Cessation of

breathing resulting from severing the ,branchial nerves and

leading to death. With the aid of applying preliminary

narcosis or c'Ocainization of the branchial nerve, it was

shown that the cause of the development of ,Y,eneral inhibition

of the central nervous system as a result of the severin of

the branchial nerves is not at all by itself a trauma but an

exclusion of afferent impulses going along the branchial nerves

and normally toning the central nervol.s system.

• Thus, in fish, we disclose the presence of a special

reflexogenic zone in the branchial area which reflexly gives

rise to respiration both to the similar sinocarotid and sortie

zones in mammals. The branchial reflexogenic zone is dominating;

it provides the activity of the respiratory centre. Its ex-

clusion leads to the cessation of respiration, to a shock-like

state andin the final analysis to death.

The branchial reflexogenic zone possesses, similar

to the sinocarotid zone, a high chemical sensitivity to adrenalin

and nicotine'.

The discovery of the vitally important role of the

branchial réflexogenic zone in fish in the regulation of res-

piration and fUnctional activity of the entire.central nervous

system made it possible to assume that also in amphibians (frogs),

44

which are closest to fish in the evolutionary scale of the

phylogenetic development of vertebrates, the branchial reflex-

°genic zone which has been transformed into the aortic zone

has preserved its.importance.

The experiments which we conducted in bamarkand in

the autumn of 1942 on Rana ridibunda in conditions of high

atmospheric temperature and bright illumination, completely

corroborate the point of view referred to. High bilateral

vagotomy leads to the cessation of respiration and a subsequent

slowly developing process of irreversible inhibition (shock-

like state) and to death. This fact is obtained so reliably

that by severing the nerves we succeeded in disclosing, with

greater accuracy than this would have been possible with the

aid of histological methods ) the course of fibres, the exclusion

of which leads to the phenomena referred to above.

By means of high and low severance of the vagus

nerves ) it was established that in Rana ridibunda these fibres

are a part of the long larangeal nerve. The results of the

high and low severance of the long larangeal nerve led to the

idea of looking further for these fibres in the rami of the

long larangeal nerve. With the aid of a binocular magnifying

glass ) we succeeded in detecting such a ramus which goes towards

the heart and ) apparently represents the aortic nerve.

Severance of this nerve led to the same results as the high

severance of the vagus or long làrangeal nerve. /308

Z r 5

With the aid of chemical action, we succeeded in

detecting also the termination point of this nerve (reflexogenic

zone) on the dorsal surface of the aortal bulb and bifurcation

of the aorta. This zone turned out to be very sensitive to

nicotine (1:500 and 1:10,000) and cyanide potassiUm (1:1,000

and 1:10,000), similar to the aortic éricl sinocartid zone in

mammals.

Later, the question arose of the analysis of the

causes of the emergence of the shock-like state of the central

nervous system. vvith what we are dealing with the results

of the stimulation of the sensory nerve when it is severed or

with the consequenceS of the exclusion of afferent impulses

• which normally tone the central nervous system?

The application of novocain on the vagus nerves of

long laryngeal nerves or area of the reflexogenic zone leads

to the same results as severance of the nerves, testifying to

the fact that the shock-like state is, apparently, the result

of exclusion. and not stimulation. Testifying to this are also

the experiments with preliminary urethane narcosis which in

removing the nociceptive effects durinc severance does not at

all prevent the shock-like effect of the severance of the vagus

nerves.

Experiments with preliminary narcosis of the spinal

cord in frogs showed that the spinal cord, isolated from higher

divisions of the. central nervous system does not, after bi-

lateral severance of the aortic nerves, disclose such a sharp

46

decline in reflex excitability as with the complete connection

of the spinal cord with the hi,:her divisions. l'his made it

possible to assume that as a result of bilateral, vaeotomy the

brain becomes the source of inhibitory influences which it

exerts on the spinal cord.

Experiments with severance of the brain of frogs

at different levels demonstrated that namely the medulla

oblongata becomès such a source of inhibitory influences after

severance of the aortic nerves.

In the article "Physiological Bases of Traumatic

Shock", Academician L.A. ureli explains the emergence in frogs

of irreversible inhibition as a result of severing the aortic

nerves by disruPting the normal balance between stimulation and

inhibition following the exclusion of the stimulating impulses

which go from the walls of the aorta which .normally oppose the •

inhibitory influences coming from some other reflex zones.

This disruption of the normal balance between

stimulation and inhibition can, therefore, be regarded as the

cause of the creation, as a consequence of severing the aortic

nerves, of a stable focus of inhibition in the medulla oblongata,

which is the source of inhibitory influences exerted by the

.medulla oblongata on the spinal 'cord and leadinE in the final

analysis to the death of the animal.

So far , we know little about the nature of irre-

versible inhibition of the central nervous system resultint-;;

from severance of the aortic nerves. Additional study of this

question is required.

47

The slow development of the process of inhibition and

the stability of this state permit us hypothesize the chemical

nature of the• process of distribution of inhibition along the

central nervous system in this case.

The fact of sharp retardation or even complete

cessation of the heart in the frog, which sets in a considerable

time after bilateral severance of the aortic nerves, indicates

the emergence of chemically active substances in the blood

channel. l'he cessation of the heart in this case cannot be

explained by neural inhibitory influences in view of the

severance of the'vagus nerves. Nor can it bu explained by

asphixiation resultinE from suffocation since with reversible /309.

cessation of' respiration resulting from curarization the heart

did not stop and scarcely retarded its automatic activity.

The interchange of gases in the frog is ensured to a sufficient

degree by cutaneous respiration.

Inhibition of the spinal cord arising as a result

of'severance of the aortic nerves in the frog, as.was shown by

the experiments, spreads from the brain to the spinal cord

intracentrally and not along sympathetic . pathways. It should

be compared not with "Sechenov" inhibition but with "spinal

shock". This "inhibitionfl e however, in contrast to "spinal shock"

is irreversible in nature and leads to final death of the animal

in 30 - 40 minutes.

Reptiles are the ancestors of higher vertebrates -

the first atmospheric-terrestial inhabitants. P'or the solution

to the basic question, the evolution of reflex cOnnections must

be studied, therefore, reptiles have a special importance.

In tortoises, we do not succeed by.means of partial

deafferentation in disclosing any single dominating reflexogenic

zone the exclusion of which would lead to such results as did

severance of the branchial nerves in fish and the aortic nerves

in amphibians and, namely, to the irreversible cessation of

breathing and inhibition of the central nervous system. In

tortoises, the respiratory centre has various reflex connections

with all afferent sYstems of the organism. The exclusion of all

of these systems separately leads only to a change in the

nature of the respiratory movements. .But the general respiratory

activity, is preserved. It should be emphasized that the afferent

systems exert not only a tonic but also an inhibitory influence

on the respiratory centre.

In contrast to fish and amphibians, in tortoises the

pressoceptor nerves (aortic and sinocarotid) do not play a

decisive role in the regulation of respiration. In vertebrates

which live in water and are supplied with branchia, the branchial

nerves play a definite roie in the defence against penetration

of poisons into the organism via the branchial apparatus and •

in the coordination of respiratory MevementS with blood pressure

in the respiring.surfaces of the branchia and With the pressure

of the water flowing past.

4:9

In amphibians ) assigned together with fish to the

group of fish-like forms, the pressoceptive aortic nerves,

analogues of the branchial nerves, still preserve their

physiological importance. But in reptiles, the first true

terrestial animals, the pressoceptive nerves lose their role

. of basic and sole stimulators of the respiratory centre. The

role of such stimulators in tortoises is taken on by other

afferent systems, primarily the'pulmonary vaaus nerves and distant

receptors.

In terrestial vertebrates, beginning with reptiles,

the pulmonary reflexes of Hering and Breuer take on a special

role in the regulation of respiration. The exclusion of vagus

nerVes in tortoises leads to periodic breathing with long

periods of apnea, with the respiratory centre becoming a little

sensitive to humoral stimUlation. The role of pulmonary re-

flexes in tortoises is still smaller than in mammals.

In terrestial vertebrates living in an atmospheric

environment, the distant receptors of hearing sight and smell

take on an especially important role. bimultaneous exclusion

of all three distant receptors leads to sharp depression of

respiratory activity and lowering of the overall activity of

the animal. jùring a lengthy period, respiratory movements

of small arriplitune and sparse rhythm occur.

In.examining data with exclusion of a significant

number of afferent nerves, we have difficulty in insisting on /310

50

the exclusive reflex nature of the activity of the respiratory

centre in tortoises. Although, at the expense of all cranio-

cerebral nerves, deafferentation led to the cessation of

respiration in our experiments, this only set in gradually:

the respiratory centre became unusually inert j its activity

only died out gradually. There is' no such picture of cessation

of respiration in fish and amphibians with the severance of

the vagus nerves. de are obliged to assume that in hiLher

vertebrates, beginnirw with reptiles, the functioning of the

respiratory centre is based on another principle than in lower

vertebrates. In reptiles, ap -earently, we already encounter the

rudiments of automatic activity of the respiratory centre. In

addition, the excitability of the respiratory centre is found

in close relationship with the presence and nature of the

afferent impulses advancinL to it. Deafferentation leads to

a sharp decline in the excitability of the respiratory centre. '

In mammals, as in reptiles, we do not succeed in

disclosing among all of the reflex connections of the respiratory

centre any one dominant connection, the exclusion of which would

lead to an irreversible cessation of respiration and general '

• inhibition of the central nervous system.

The various severins of afferent nerves (distant

receptors, vagus, glossopharyne:eal, nressoceptive and spinal

receptors) which we have performed show that afferent nerves

exert both a tonic and inhibitory influence. A massive

51

exclusion of afferent sYstems leads to a sharp depression in

the activity of the respiratory centre and the entire central

nervous system. In addition, there is no quick Cessation of

respiration but only a low dying out of its activity.

The basic principle of activity of the respiratory

centre in mammals, as in reptiles, is its automatism. The

excitability of the respiratory centre is in close relationship

with the presence and nature of afferent impulses advancing to

it. Deafferentation leads to a sharp decline in the excitability

of the respiratory centre, riht to the complete - cessation of

its activity.

Of great interest is the fact that among the species

of animals studied by us, two groups have been disclosed with

different degrees of perfection in the respiration regulation

apparatus, mainly rodents (mice, rats, guinea pigs and rabbits)

which belonË: to more primitively structured mammals and dogs

and cats which belong to hiher mammals. Uri the phylogenetic

ladder of development of mammals, rodents branch out from the

general tree very early, beginning with the primary placentals,

whereas, canine and feline animals represent a hiher rung of

development of predatory mammals. This was also reflected in

the data we obtained on the results of severance of afferent

nerves. Rodents, in contrast to higher mammals - dogs and cats -

possess an astonishing sensitivity to bilateral vagotomy.

52

As a resuatof such an operation in rodents,

respiration took on a typical non-vagus nature, the entire

skeletal musculature was involved in the act of 'respiration.

Depression of the respiratory centre gradually set in, accom-

panied by inhibition of the central nervous centre which, in

1 - 11' hours, led to the complete cessation of respiration

and death.

Vagotomized tortoissE, however, continue to live

for many days. •

Thus, in rodents we note to sonie degree a preser-

vation of old coordination relationships which are established.

in fish and amphibians, namely, the close relationship between

the activity of the respiratory centre and vagal afferent

impulses with the only differencebeing that . in fish and

amphibians the branchial and pressoceptive reflexogenic zones

have a decisive importance, whereas, in rodents this role

passes over to the pulmonary vagus nerves.

New born rodents (mice, rabbits, and guinea pigs)

.disclose a still greater sensitivity than mature rodents to

bilateral vagotomy which in them leads a very speedy total

cessation of respiration and to death.

New born kittens and pups (higher mammals) disclose

longer survival after bilateral Vagotomy (up to 24 hours or

more). However, they-all die invariably after this operation.

5 3

In contrast to this, mature dogs survive up to a year or more

with certain operative methods and special conditions in the

care of the animals (Acad. I.F. Pavlov, Gheshkovi Kachkovskii).

Vagotomy in mammals not only leads to a change in

the rhythm and amplitude of respiration but also sharply

reduces the ek.citability of the respiratory centre to humoral

and reflex stimuli. .After vagotomy, the respiratory centre

becomes sluggish and inert and reacts poorly to hyperthermia.

The severance of all posterior cervical roots with

subsequent transverse severancece the spinal cord at the

boundary of the thoracic and cervical parts leads only to the

quickening and not to the cessation of respiration. However,

subsequent vagotomy after a preliminary exclusion of all

spinal afferent systems leads considerably faster to the

cessation of respiration.

The preliminary exclusion of distant receptors

in pups and mature dogs sharply increases the sensitivity

of the respiratory centre to subSequent vagotomy and sever-

ance of the sinocarotid nerves which lead to a quick cessation

of respiration and to death.

With the isolated seVerance of the vagus and pres-

soceptor nerves other afferent'systems (dietant receptors

and spinal afferent systems) replace thenrand continue for

.some time to tone the respiratory centre and maintain its

functional activity.

54

The regular experiments Which we conducted on dogs that

showed.the exclusion of distant receptors by severini ... the visual

and olfactory nerves and destroying the labyrinths leads to

a sharp decrease in the total activity of the central nervous

system, disorder in motor coordination and disruption of res-

piration regulation, dissociation of costal and abdominal res-

piration and serious distrophic disorders which brin death

to the animals in the final analysis. The fact of the appear-

ance of such serious disorders with the e«:(clusion'of distant

receptors testifies to the large role which the distant receptors

play in the toning of the central nervous system and in the

stimulation of all vital activities of the organism.

CONCLUSION

In contrast to the scheme of Lumsden, we, on the

basis of the experimental data we.have obtained, present a the

scheme of evolution of.functional relationships of the respiratory

centre not only as an evolution of structure but as an evolution

of the reflex connections of the respiratory centre under the

influence of which the excitability to humoral stimuli changes

und the capacity of the respiratory centre for automatism is

manifested. The evolution of the respiratory centre traverses

the historical path from a reflex respiratdry act in lower

vertebrates • o perfect automatism in higher vertebrates.

55

The fine adaptation of the activity of the res-

piratory centre in the regulation of supply of oxygen to the

organism and removal of carbon dioxide in accordarce with the

physiological requirements of the organism, which depends on

the rate of the metabolic processes, become posle only when

the respiratory centre, due to an incre,Àse of its sensitivity, /312

begins to function automatically under the direct influence

of the metabolic processes in the centre itself.

The reflex innervation apparatus of respiration

in lower vertebrates cannot adapt itself to such a fine deFree

to the rate of flow of the metabolic processes. Iherefore,

the evolution of the functional relations oU the respiratory

centre from a reflex respiratory act in lower vertebrates to

perfect automatism in hi;:hur mammals should be considered a

.progressive fact of the hihest degree.

The innervation relations of the motor apparatus

traverse another historical path of evolution, namely, from

peripheral automatism to the reflex act. ror tne moor apparatus

"the chance from peripheral automatism to the reflex act, which

is subordinated to the central nervous system, to a great

extent provides speed, exactness and refinement in a reaction

to stimuli from the quickly changing outer environment" (Orbeli)..

Common to peripheral automatism of effector organs

and automatism of the-respiratory centre is their dependence

of the chemical .Composition of the environment.

56

In this connection, we should particularly stress

the striking sensitivity of the respiratory centre to the

pressure of gases (especially CO 2 ) in the blood and in the

environment which•directly wash it. In this, the respiratory

centre differs from other nerve centres which', althouFh they

also react to the fluctuation in gas content in their immediate

environment, do not react to the same degree nor in the same

manner as the respiratory centre.

Also common to the peripheral automatism or the

effector organs and automatism of the respiratory centre is

the intimate mechanism of. the emergence of automatic rhythmic

states of excitation. It is conditioned by fluctuations in

sensitivity associated with refractivity in different 2hases

of activity.

There is also a principal difference between the

peripheral automatism of the heart and the automatism of the

nervous centre (respiratory). Although automatism lethe heart

is regulated by the nervous system, it is realized in a very

perfect form in an isolated heart as well. •

Btït. automatism of the respiratory centre is.con-

ditioned by the presence and nature of the current of afferent

toning impulses which advance towards the respiratory centre.

Deafferentation of the respiratory centre sharply decreases its

excitability to humoral stimuli and together with this decrease

its capacity for automatic activity.

57

Automatism and the reflex principle in the activity

of the respiratory centre in higher mammals by no means oppose

each other as two mutually exclusive mechanisms. un the con-

trary, we emphasize their close interdependence. In essence,

it is. impossible to iMagine perfect automatic .activity of the

respiratory centre without the influence of various afferent'

impulses upon it.

The two basic functional mechanisms of the central

nervous system - the reflex Mechanism which is based on the

inflow of afferent impulses from the periphery and the auto-

matic mechanism which is based on the influence of humoral

stimuli directly on the nerve centre - are in actuality closely

interwoven and interrelated in a single dialectic %I-1On".

In examining the course of development of the

functional relationship of the respiratory centre, we are

greatly interested is the role of different afferent systems

in the stimulation of activity of the respiratory centre in

the different stages of phylcwenetic development of vertebrates. 7313

At lower stages in the evolution of vertebrates, the activity

of the respiratory centre is stimulated by the inflow of afferent

impulses from the vascular reflexogenic zones. The vascular

system, the mOvement of blood along which is determined by the

automatically working heart, is'itself a source of afferent

impulses which reflexly tone the activity of the respiratory

centre in lower vertebrates. •

5 8

In amphibians, which together with fish belong

to . the general group of fish-like forms, the pressoceptive

nerves - analogues of the branchial sensory nerves - still

retain their physiological meaning. But in reptiles, the

first true terreetial vertebrates, the pressoceptive nerves

loSt their role . of basic and sole stimulators of the res-

piratory centre. The role of such stimulators in hiher

vertebrates is taken on by other afferent systems - primarily,

the pulmonary vagus nerves'and distant receptors. In tortoises,

the stimulating influence belongs in equal degree to all afferent

systems, primarily, to the distant receptors which acquire a

special role in terrestial animals living in an atmospheric

environment.

In mammals, the pulmonary vagal reflexes of Herinif

and Breuer acquire an especially important. role. Exclusion

of these reflexes renders the - respiratory centre inert and

little sensitive to humoral and reflex stimuli. The distant

receptors and also the spinal afferent systems play an unquestion-

ably . important role in toning the respiratory centre. Their

preliminary exclusion sharply increases the sensitivity in

the animals to the subsequent severance of the vagus and

pressoceptive nerves.

59

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* Direct transliteration from Russian. Possible English renderings

are Holden and Priestly. - - Translator.

11

It

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66

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German and French E.C. 4.11.1969 bibliogr. titles

GERMAN: 34. Baglioni: Comparative physiology of respiratory

motions of vertebrates.

35. Babak: The question of the development of

respiratory motions 'in fish.

36. Bayer: Control,of breathing.

38. Bethe: General anat. and physiol. of the

nervous system.

39. The theory of central • unction. Brown:

42, The reflex function of the central nervous system.

43. Bracke: Refractory phase and rhythmicity.

44. Buchanan: is the reflek strychninetetanus etc.

45. Buddenbrock: Outline of comparative physiology.

FRENCH: 52. Flourens: Experiments on the nervous system.

GERMAN; 62. Hering: The autoregulation of respiration through

n. vagus.

IT 63. Hess: The control of breathing.

FRENCH: 64. Haymans: The carotid sinus and the other

reflexogenous vasosensit ive zones.

GERMAN: 67. Koch: The reflex autoregulation of circulation.

69. Physiology of the spinal' and encephalic marrow• .

75. .Matula: Investigations of the performance of the .

nerve centres in Decapoda.

* r 67

-2

tt

It

IT

GER1JAN:79. Rosenthal: Respiratory motions and their connection

with nervus vagus.

85: Traubel: Physiology of the nervus vagus.

86: Uexküll: The origin of rhythm in ani:lals.

89: Winterstein: The automatic activity of the •respiratory

• centres.

90: The reaction theory of respirtory control.

92: Verworm: Physiology of the central nervous system.

'93: Verworm: Fatigue, exhaustion and relaxation of the

• nervous centres of the spinal narrow.

• .