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[No. 150.— [July 15, 1826.] LECTURES ON THE ANATOMY, PHYSIOLOGY, AND DISEASES OF THE EYE. BY MR. LAWRENCE. London Ophthalmic Infirmary, Moorfields. LECTURE XXII. Affections of the Iris. Glaucoma. Hy. drophthalmia. Gentlemen, IN some instances the iris is entirely de6cient. One or two cases of this kind are recorded, and two have come under my own observation, in which it seemed that the part did not exist in the eye ; in these cases there have been partial opa- rities of the capsule of the lens ; not, hovever,reqniring any operation. There are sometimes natural differences of colour between the two irides, and between different parts of the same iris. In a grey or light blue iris, you will some- times see one-third or one-fourth of a light brown. You must be aware of these natural diversities, for I have al. ready said that inflammation produces changes in the colour and figure of the iris, and if you were not apprized of the for- mrrfact you might be led into mistakes. There are sometimes, natural differences in the shape of the pupil, that opening being continued as far as its ciliary mar- gin on one side ; thus you may have a triangular pupil, with the apex turned tuwards the nose, or towards the cheek, and in other respects the eye may be perfectly formed. The iris frequently exhibits a number of dark-coloured spots upon its anterior surfuce, and althongh they do not form a part of its original structure, they can hardly be said to be the consequences of disease. I never saw them on the irides of young subjects; generally about the middle or after the middle period of life, but I will not say that they are the result of disease. Prolapsus or Procidentia Iridis. A protrusion of the iris (prolapsus vel procidentia iridis,) is a very frequent oc- currence, and important in its conse- quences. The iris floats naturally in the aqueous humour, and you will easily con- ceive that if the substance of the cornea should be destroyed by sloughing or by uleeration, that the aqueous humour will escape, and the iris force into the opening, and so produce a sort of hernia of the iris, especially if any pressure be made upon the globe of the eye, or by the spasmodic action of the muscles of the globe. This protrusion of the iris is sometimes called staphyloma iridis. When the whole of the cornea sloughs, as it does sometimes in gonorrhœal or purulent oplathalmia, you will have the whole of the iris protruding in an irregular mass at the front of the eye, and that has been called staphyloma racemosum from the resemblance which it has been supposed to bear to a bunch of grapes, the word rasemosum being immediately derived from the substantive racemus, which sig- nifies a cluster. When the inflammation subsides, the irregular tumour sometimes shrinks, the cornea becomes opaque at the point of pro- trusion, and the iris is permanently adhe- rent to the posterior surface of this opacity. The point of adhesion, and the situation of the previous protrusion are marked by a dark spot in the centre of the opacity. If the tumour should not gradually retire in this way, if it should remain perma- nently projecting, and if it should continue to form an irregular protruded surface, and irritate the eye, it will be necessary to remove the projection by shaving it off with a cataract knife ; but, generally speaking, this procedure is not neces- sary. The prolapsus iridis usually embraces only a part of the iris ; a portion of this structure passes through the opening

LECTURES ON THE ANATOMY, PHYSIOLOGY, AND DISEASES OF THE EYE

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Page 1: LECTURES ON THE ANATOMY, PHYSIOLOGY, AND DISEASES OF THE EYE

[No. 150.— [July 15, 1826.]

LECTURESON THE

ANATOMY, PHYSIOLOGY, AND DISEASESOF THE EYE.

BY MR. LAWRENCE.

London Ophthalmic Infirmary, Moorfields.

LECTURE XXII.

Affections of the Iris. Glaucoma. Hy.drophthalmia.

Gentlemen,IN some instances the iris is entirely

de6cient. One or two cases of this kindare recorded, and two have come undermy own observation, in which it seemedthat the part did not exist in the eye ; inthese cases there have been partial opa-rities of the capsule of the lens ; not,hovever,reqniring any operation.There are sometimes natural differences

of colour between the two irides, andbetween different parts of the same iris.In a grey or light blue iris, you will some-times see one-third or one-fourth of a

light brown. You must be aware ofthese natural diversities, for I have al.

ready said that inflammation produceschanges in the colour and figure of the iris,and if you were not apprized of the for-mrrfact you might be led into mistakes.There are sometimes, natural differencesin the shape of the pupil, that openingbeing continued as far as its ciliary mar-gin on one side ; thus you may have atriangular pupil, with the apex turnedtuwards the nose, or towards the cheek,and in other respects the eye may beperfectly formed.The iris frequently exhibits a number

of dark-coloured spots upon its anteriorsurfuce, and althongh they do not form apart of its original structure, they canhardly be said to be the consequences ofdisease. I never saw them on the iridesof young subjects; generally about the

middle or after the middle period of life,but I will not say that they are the resultof disease.

Prolapsus or Procidentia Iridis.

A protrusion of the iris (prolapsus velprocidentia iridis,) is a very frequent oc-currence, and important in its conse-

quences. The iris floats naturally in theaqueous humour, and you will easily con-ceive that if the substance of the corneashould be destroyed by sloughing or byuleeration, that the aqueous humour willescape, and the iris force into the opening,and so produce a sort of hernia of theiris, especially if any pressure be made

upon the globe of the eye, or by thespasmodic action of the muscles of the

globe. This protrusion of the iris issometimes called staphyloma iridis. Whenthe whole of the cornea sloughs, as itdoes sometimes in gonorrhœal or purulentoplathalmia, you will have the whole ofthe iris protruding in an irregular massat the front of the eye, and that has beencalled staphyloma racemosum from theresemblance which it has been supposedto bear to a bunch of grapes, the wordrasemosum being immediately derivedfrom the substantive racemus, which sig-nifies a cluster.When the inflammation subsides, the

irregular tumour sometimes shrinks, thecornea becomes opaque at the point of pro-trusion, and the iris is permanently adhe-rent to the posterior surface of this opacity.The point of adhesion, and the situationof the previous protrusion are marked bya dark spot in the centre of the opacity.If the tumour should not gradually retirein this way, if it should remain perma-nently projecting, and if it should continueto form an irregular protruded surface,and irritate the eye, it will be necessaryto remove the projection by shaving it offwith a cataract knife ; but, generallyspeaking, this procedure is not neces-

sary.The prolapsus iridis usually embraces

only a part of the iris ; a portion of thisstructure passes through the opening

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the cornea, and forms a dirty brownishtumour, and this tumour by being rubbedrepeatedly against the lids, will producesometimes inflammation of the lids, andthus affect the whole eye, producing con-siderable pain and intolerance of light.The irritation produced by the pressureof the edges of the aperture upon thedelicate textnre of the iris, causes adhe-sion of it to the sides of the aperture ;the irritability goes off, and the tmnour

produced by the protrusion, sinks in. Stillthe iris remains adherent to the part inwhich it is engaged, and the ultimate ap-pearance of the part is that of a black orbluish point on the cornea, surrounded byan opaque margin. You may see cases

in which more than one such points are

formed on one eye.

Treatment of prolapsus iridis.—It re-quires in general no particular treatment.You mut remove the inflammation as youwould in any other case. We cannot re-

place the prolapsed iris ; it would notcome out, unless there was some pressurefrom behind; you cannot succeed in re-

storing it in opposition to this force, andsuch an attempt would only aggravate themischief. In a short time the iris becomesadherent to the edges of the cornea. Inever saw an instance of prolapsed iris inwhich it could be returned into its naturalsituation. All you can do is to reduce theinflammation and irritation in the part,and wait for the natural process of ttie

shrinking and reduction of the tumour,nntil there is only the small dark-cotouredpoint remaining. Now the small brownishtumour which the iris forms may not sub-aide when the irritation of the eye goesoff ; it often remains prominent and youmight in that case touch it with a pencilof the nitrate of silver to cause it to col-

lapse. The partial prolapses of the irisin which the application of the nitrate ofsilver is admissible are when they are verysmall, when the tumour is about the sizeof a fly’s head, which has been calledmyocephalon; when larger or about thesize of the head of a nail, it is calledclavus; great care must be observed inusing it, as it may do much harm if itshould not do good.The prolapsus iridis may produce very

tsnfavourable changes in the state of thepupil, and will either impair or destroyvision. Prolapsus iridis may produceeither an oval or elongated figure of thepupil ; it may draw down the pupillarymargin so as to contract the pnpil verymuch or completely to close it. Youhave, occasioned by this prolapsus, a dis-placement of the pupil, a contraction ofthe pupil, and in addition to these change s

you have an opaque margin surroundingthe adherent edges of the iris and cornea;and these changes altogether, produce avery imperfect state of vision, and inother instances completely destroy it. A

mere prolapsus situated near the marginof the cornea, or above the situation ofthe pupil, or on either side of the pupil,does not interfere much, generallyspeaking, with vision ; whilst a slightprolapsus situated immediately oppositethe pupil, will very much interfere with it.Now with respect to the changes in the

figure of the pupil, that is of itself a eir.cnmstance of no consequence to the func.tions of the eye ; and in the changes offignre arising from prolapsus or fromiritis, it does not appear to be a matter ofmuch importance whether the pupil is

triangular, square, or oblong, as they arealso capable of transmitting Jight to theinterior of the organ. It is very commonto hear persons inquire, after the opera-tion for cataract has been performed," is the pupil circular?" as if that were themost important point to which the atten-tion should be directed ; but the fact i,that it is no matter whether the pupil iscircalar or not ; any other figiire wiU dojust as well.When the tns adhere o the posterior

surface of the cornea, which it frequentlydoes after serious inflammation affectingthe cornea, and which it necessarily doesafter ulceration of the cornea with pro.tapsus ; that adhesion is called synechiaanterior, the Greek term synechia beingequivalent to adhesion, and the epithetanterior being added to distinguish itfrom the adhesion of the iris to the cap-sule of the crvstalline lens. This ante-rior adhesion is generally accompaniedwith leiicotna of the cornea, and it usuallyhappois, when there is a dense opacityof the entire cornea, that the iris is moreor less adherent to its posterior surface.There is no remedy for this adhesion; yoncannot detach it any more than you candetach an adhesion of the intestines tothe peritonaeum, or of the lung to the

pleura. The same observation will applyto the synechia posterior, or the adhesionof the ptipillary margin to the capsule ofthe lens; this adhesion is produced bylymph effused under inflammation fromthe pnpillary margin of the ins. The con-nexion may be more or less, it may ad-here in one, or in several points only, orthroughout its whole circumference. Itis frequently attended with capsularopacity, or the formation of the adven-titious membrane before described, as

Ibeing sometimes found in iritis. Thisposterior adhesion, like the anterior, isirremediable. But in the cases of con-

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traction of the pupil from prolapsus iridis,or from synechia anterior; or of its beingcoveredbyleucoma ; and in cases of con-fracted pnpif, from partial synechia pos-terior, unattended by the formation ofadreutitions membrane, or opacity of thecapmle, we are often able to renderthe most essential service to vision by thense of belladonna to dilate the pnpil. Ifprolapsus shonld have taken place, andif, in conjnnction with that prolapsus,there should be opacity of the cornea co-vering the pupil, you may often, by thebelladonna, dilate the aperture so as to

get its circumference beyond the opaqnespot. Even in cases where there has beenpartial opacity of the capsule, and whop ethe pnpillary margin appeared at first

sight adherent throughout, it has beenoften found, on applying the belladonna,that a small portiou of the margin hasremained free, and capable of dilatation,with gleat improvement of sight. We

ought not, therefore, to sav, that thpsecases are irremediable; and I have oftenbeen surprised to see how well patientshave been able to see through a verysmall pupillary aperture. I have seen pa-.tients enjoying very tolerable vision, whenthe opening in the iris has not been largerthan a small pin’s head. In these cases,if yon find that belladonna will give the

patient vision, or improve the state of

vision, you must employ it once in twenty-fonr hours, to keep np its effect perma-nently. Some of the cases I have men-tioned, admit of no other remedy, butthere are others which admit of othermodes of relief, as bv making an artificialpupil, of which I shall have to say morehereafter.In systematic works on diseases of the Ieye, you will find a contracted state of

the pupil, and an nnnatnrally dilated stateof the pupil spoken of, the first beingcalled myosis, and the latter mydriasis.Now it is not uncommon to meet withindividuals who, being accustomed to lookat extremely minute objects, have a verycontracted pupil, yet fully sufficient forthe purposes of life. ,

A preternaturally dilated state of thepupil, is not a common occurrence in thesound condition of the eye; it is mostcommonly dependent on a loss of sensi-hility in the optic nerve. If the ptipil bedilated with a sound nerve, the sightmay be benefited by looking through akt of pasteboard darkened within, andhaving in its centre a small opening,corresponding to the natural size of thepnptt. It might be fixed into a frame,and worn as a spectacle.Among the consequences of inflamma-

6,)ti affecting the internal paft of the

globe, must be reckoned It)) opaque statedof the capsule and of the lens itsetf,or a capsnlo-lenticalar cataract. Tlrereis generally considerable thickening ofthe capsule of the lens from depositioninto its textnre, or on its surface; andwith this opacity of the capsule, thereis generally adhesion of the iris. Thereis no remedy for this kind of opacity ;and in cases in which the inflammationhas been so serious as to produce theseeffects, it almost invariably affects theretina also, and makes it amanrotfic.The term of glaucoma was formerly

given to cataract, but is no longer em-ployed for that purpose ; we use it novoto denote a certain affection of the vitre-!ous humour consequent on inflammationof that part of the eye, attended withan alteration in the colour of the pupil.It is an important affection, because itdirectly interferes with the transmissionof light to the retina, and because it maybe mistaken for cataract; the inflamma-tion which produces glaucoma, often, in-

deed generally, extends to the retina,and causes it to be amaurotic.

,5ynipto)ns.-Tlie first symptom of glau-coma is a pain in the head, usually situa-ted over the brow, and frequently the pa-tient describes it as extending quitethrough the forehead. This pain inmany cases Is very severe, but in othersnot so strongly marked. In conjunc-tion with this pain., the patient begins tocomplain of dimness or of weakness ofthe sight, and if you examine the eye atthis time, yon find that instead of ex-hibiting its natural deep black colour, the,pupil is ofa greeriish,mttddy green, oryel-lowish green colour. A discolouration,

which if yon look at it in a strong lightwill appear like a yellowish met,illic re-flection from the bottom of the eye, i6looks almost as if there was a piece of me-tal quite at the bottom of the eye; thepupil at the same time is generally ratherdilated, and the iris sluggish iii its mo-tions. Such are the symptoms of glaucoma.Now, the state of’ vision is different indifferent instances ; in some yon will have!an alteration of the pupil distinetly pro-dufed, and yet the vision may remain

tolerably perfect. In other ca:esyou willifind that vision is entirely loxt, with’

apparently no more discolouration ofthe back part of the eye, or alteration ofthe pupil, than in the former instance.Glaucoma is an inflammation of the vi-treons humour, which changes its textur eand colour ; now when you consider howclosely the retina lies upon this; humour,you ean have no difficulty in accordingfor their being both inflamed:; indeed itwould be more difficiat to explain how

2 K 2

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they could be separately inflamed: whetherthey are both inflamed from the com-mencement of this affection or not, if theinflammation of the vitreous humour beallowed to go on, and be not checked, itwill proceed to involve the retina, andcause such changes in its strncture as torender the eye permanently amanrotic.During the progress of such a case, thevision becomes gradually worse andworse ; the discolouration of the pupil,or rather of the fnndus of the globe be-hind the pupil, becomes more considera-ble ; the iris becomes more and moresluggish; until it is at last motionless,and vision is entirely lost. The affectiondoes not always stop at this point, butsometimes attacks the lens, and rendersit opaque, so that it is no uncommon

thing for cataract to occur subsequentlyin an eye which was originally attackedby glaucoma. The cataract thus pro-duced is greenish, yellowish, or dirtywhite, (cataracta viridis or glaucomatosa.)

Causes,—With respect to the causes ofthis affection, we can point out nothingpeculiar as contributing to its occurrence.It takes place at or after the middle pe-riod of life, and in persons not of themost healthy character. It appears tome to be merely a chronic form of thesame inflammation which I have de-scribed to you as the arthritic inflam-mation affecting the posterior coats ofthe eye; the changes which occur in theretina, vitreous humour and lens, as theconsequences of that inflammation, arerapid and sudden, whilst in the presentcase the disease has a slower progress,and the changes are more slowly pro-duced ; but it certainly does appear tooccur more frequently in such persons asare liable to gout and rheumatism thanin others. It is of considerable import-ance that you should be well aware of thecharacteristics of this affection, since itis so liable to be mistaken for cataract.

Diagnosis.—The discolonration of thepupil arising from glaucoma and cataract,may be distinguished by the tint of colourwhich it exhibits; in glaucoma, it is

green or of a yellowish green, and if yonlook at the eye laterally in glaucoma, youcan see no discolouration, whilst incataract the pupil looks grey, or of agreyish white, and it remains so whetheryon look at the eye laterally or not. Theloss of vision in glaucoma is not in directproportion to the change of colour of thepupil; with an inconsiderable change inthe colour of the pupil, you may havevision entirely destroyed or very seriouslyimpaired; but in cataract there is a directproportion between the state of opacity I

or change of colour and the injury to

sight. In cataract, vision is best in amoderate or weak light ; but in glaucomathe vision is most perfect in a strong light,because in glaucoma as the retina is be-come less sensible, more light is requiredto make an impression on it. These arethe principal distinctions between glau-coma and cataract; great care is neces.

sary sometimes to be able to speak de-cidedly as to the nature of the disease,especially in the early or incipient stagesof either affection.

Prognosis.—The prognosis in glaucomais unfavourable ; we have no means ofchanging the condition of the vitreoushumour when it has once lost its trans.

parency ; we cannot bring it back againto its natural appearance ; we cannotrestore the vision which has been lost,and all we can expect to do, is to pre-

( serve the little sight which remains.Treatment.-Beer says that no treat.

ment will be of any effect in preventingcomplete amaurosis ; but I do not con.sider’that observation to be quite correct.There is a decided congestion about thebrain and orbit, and the removal of thatcongestion is attended with considerablebenefit. The treatment must he decidedlyantiphlogistic, yon must take blood bycnpping; give active purgatives, andalterative doses of mercury; the patientmust be put upon a regulated plan ofdiet, and avoid using the eye. If youfollow up this plan of treatment, you willprevent any decided advance of the dis-ease. In the first place, where there isactive congestion going on, the patientwill express himself as having deriveddecided relief from such treatment; andI have seen cases of glaucoma, which intwo or three years, by attending to theparticulars just mentioned, have shownno advance of the affection.

[Mr. Lawrence detailed some cases

illustrating the progress and treatmentof glaucoma, and showing the effectwhich this change of the vitreous hnmonrsometimes has in pushing forward thelens and iris against the cornea, and in

producing slow inflammation of the iris.]

Synchysis Oculi.There is another change occurring in

the vitreous humour, the nature andcauses of which are obscure: it is amelt-ing down, or conversion of it into a fluidstate; it is called synchysis, a Greekword, which means melting. It may bethe chronic result of long continued in-ternal inflammation, but it is sometimesa gradual change in the consistence ofthe vitreous humour, unconnected with

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Inflammation. The fluid has sometime,a brownish discolouration. The iris is lit-tleaffected in its colour or figure; but,instead of the natural motion of the pupil, Bor rather instead of the gradual contrac-tion and relaxion of the fibres of the iris,there is a peculiar tremulous or oscillatorymotion of the part the natural supportwhich the iris receives is lost, and henceit shakes backwards and forwards like a

rag in a bottle of water. It is an ap- ipearance at once very striking and cha-racteristic of the affection. It often hap-pens that the lens loses its transparencyin these cases, and cataract is added tothe other affection ; the capsule of thelens has been found converted into acretaceons substance in snch instances,which could be distinguished by its pecu-liar yellowish white colour. This stateof the vitreous humour has been consider-ed as the result of some internal inflam-mation, and Beer seems inclined to as-’cribe it to the effect of mercury, sofreely used for the removal of that in-,ternal inflammation. I cannot say thatI have ever seen an instance corrobora-tive of this opinion, which seems to bemerely grounded on the antiquated andabsurd notions of resolvent and dissolventpowers of the remedy in question. Ihave given mercury very largely in a vastJmmher of such cases, and should havehad ample opportunities of seeing it, ifsuch an effect had been produced. ,

In a few instances I have seen thistremulous motion of the iris occur afteroperation for cataract. Usually, this dis-solved state of the vitreous humour indi-cates a diseased condition of the internal

parts of the eye, and the truth is that theretina has lost its sensibility in such cases.Sllch a state of the vitreous humour doesnot admit of any benefit, and if a cata-ract should be present no relief can beafforded by an operation. ,

Hydrophthalntia.This is a state of the eye in which the

’’

whole of the globe becomes enlarged,from an increase of its humours, parti-cularly of the aqueous : is is called hy-drophthalmia, and sometimes bnphthal-mus, from its increased size. The corneais more or less opaque in some instancesin this state of the eye ; and the eye, inaddition to this, is frequently amaurotic.Itappears to be produced by long-continued chronic inflammation of the inter-nal parts of the eye, occasioning an in.creased secretion of the various humours,and thus giving rise to this increase inbulk. Hydrophthalmia may produce thetame incollvenience as staplyloma; the r

projection of the eye becomes a source of, mechanical irritation; or it may be sub-ject to attacks of inflammation, whichmay also sympathetically affect the othereye. Under such circumstances we maytry the palliative mode of relief, such aspuncturing the cornea, or puncturing theglobe behind the cornea, so as to let outa part of the fluid. It is probable thatrepeated punctures of the globe might,by allowing the fluid to escape, cause

ultimately a collapse of the globe, andthus get rid of all further inconvenience;but if it should be found that this planwill not succeed, I see no reason why thesame operation as that practised for thestaphyloma corneae, should not be per-formed, especially if the cornea shouldbe opaque; the globe would then col-

lapse, all source of irritation be removed,and the deformity be remedied by usingan artificial eye.

I Varicose Ophthalmarz is a term some-

times used, but the only state of the eyein which we observe the vessels of theeye property varicose,. is that inflam-mation of an arthritic kind affecting theposterior coats of the eye. When the eyehas been for some time suffering underthat inflammation, some varicose trunksof vessels appear upon the surface of theorgan; so that the varicose state of the

vessels does not make its appearanceuntil the inflammation has begun to suh-side, and then it cannot be catted a vari.cose ophthalmia, but merely a changeproduced as the consequence of the pre-vious inflammatory action, and which isgenerally found to happen when the eyeis completely amaurotic.When the eye has been the seat of

general inflammation and suppuration, orwhen it has been the seat of destructivenlceration; as the consequence of puru-lent or gonorrhœal ophthalmia ; when thecoats of the eye have collapsed in con-

sequence of the operation for hydroph-thalmia., or staphyloma, the coats shrinkup and retire within the orbit, the size ofthe glohe is reduced to very diminutivedimensions, almost to a mere tubercle ;and such a state of the eye has beencalled consumptio purulenta oculi. There isanother species of shrinking of the globe,in which the globe, without suppurationor any obvious change of structure, un-dergoes absorption, and a gradual dimi-nution of size; such a state is calledatrophia 6culi. This atrophia will takeplace after various inflammations; it willtake place as a consequence of severe in.ternal inflammation, in which the func-tion of the retina is destroyed, and it

appears that the eye, like the other or-

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gans of the body, undergoes a gradualabsorption and decay when it is renderedincapable of executing its function. Incases of internal inflammation, producedby penetrating wounds of the eye, atro-phia is a frequent occurrence. When thisatrophia commences, you may feel the

globe soft and flaccid, and when the lidsare closed you may observe a depressioninstead of the ordinary convexity. The

eye will continue to shrink up until itcomes to almost the size of a large pea,or bean, and in the centre of this struc-ture you may perceive a small spot of thecornea remaining, and somewhat of theappearance of an iris. It may be con-sidered to be the favourable terminationof a case of internal inHammation ; of sncha case, I mean, in which the functions ofthe internal part of the organ have beendestroyed,becausethe patient is no longerliable to the risk of staphyloma, or pro.trusion of the globe, to cause irritationor relapses of a dangerous inflammatoryprocess. The state of atrophia is, in itself,remediless ; I have never seen a case inwhich, by any method, the progiess ofthe affection eould be put a stop to.

LECTURESON THE

THEORY AND PRACTICE OF PHYSIC,

BY DR. CLUTTERBUCK.

Theatre, General Dispensary, Aldersgate-street.

LECTURE XXXII.

Diseases of the Absorbing System.Gentlemen,THE food having undergone the neces-

sary changes in the organs of digestion,by which it is converted into a I’niJk-likeflnid’termed chyle, we have next to tracethe route of this from the alimentarycanal into the left subclavian vein, inorder to be mixed with the general massof blood, The lacteal vessels, opening Ievery where on the internal surface ofthe small intestines, are the immediatechannels through which the chyle entersthe general system. Now as these ves-sels make a part only of the generalapparatus by which foreign matters areintroduced into the body,and as this orderof parts are peculiar in their structure aswell as in their office, the diseases towhich they are liable cannot be suffi-cieutly understood, without brietfy ad-

verting to the physiology of these parbaltogether.The absorbing system, then, consists of

a set of vessels, the principal trunks ofwhich enter the great veins near to the

heart. From these trunks, the absorbentsramify throughout the body, in company,for the most part, with the blood vessels.They are, however, much le.s conspicuousthan these, partly on account of theirminuteness and transparency, and partlyfrom the colourless nature of the fluidthey mostly convey. The absorbing systemis commonly divided into two branches;.the one opening, as before observed, up-on the internal surface of the alimentarycanal, for the purpose of absorbing or

taking up the nutritious and digestedparts of the food in the form of cliyle, andwhich, from the white colour of this fluid,are termed the lacteal absorbents; theother branch, the lymphatic absorbQuts, isdistributed every where throughout thebody, opening on every surface, and iutoevery cavity and interstice, ready to takein such matters as are presented to themThe fluid absorbed by the latter beingcolourless like water, they have beentermed lymphatics accordingly, and some-times interstitial absorbents ; though thisterm, of course, does not apply to thosewhich open into the greater cavities, orupon the external and other surfaces ofthe body. These two branches, however,of the absorbing system, discharge them-selves into one common trunk, the thora-cic duct, as it is called, placed along thefront of the spine, and are in all essen-tial respects the same. The absorbentsresemble veins more than arteries, the

fluid they convey moving, like the venousblood, from the extreme branches to.

wards the trunks ; while, like veins, theyare also furnished in various parts withvalves that open towards the heart, so asto prevent a retrograde course oftheflnid,when they are subjected to mechanicalpressure of any kind.The function performed by this order

of vessels, is sufficiently ascertained.-They are in fact the principal, if not theonly channels, by which foreign mattersmake their way into the system. Theyalso serve to take up the lymph or fluidthat is constantly escaping from the ex.haling extremities of the arterial system,into the different cavities and intersticesof the body.The manner in which they accomplish

their purpose, is however a matter ofdispute among physiologists; some ofwhom consider them as mere pa6,iivetubes of conveyance, while others, withmore probability, imagine them to heendued with an active or muscular power,