~~~ l| | l ~~~~~~~~~~~~~~~- - 4FIGURE 1. Galvani's first experiment. (From Ref. 2, by permission)

The discovery of bioelectricityand current electricityThe Galvani-Volta controversy

Although the history of static electricity goes back to theancient Greeks, prior to the era of Galvani and Volta nosource had been discovered that could deliver a continuouselectric fluid-a term that implies both charge and current

L. A. Geddes, H. E. Hoff Baylor College of Medicine

Amid the tumultuous confusion and complexity of with all the array of modern techniques at our com-modern events, it is difficult to acquire the general mand, clearly still can gain much by noting andhistorical perspective so important to the scientist emulating the ingenuity, inspirational qualities, andand the engineer of pioneering nature. Yet a broad tenacity of purpose of these great pioneers.vision of the past is a most valuable asset to the work- Present-day investigators may also marvel at theers and inventors of today. It forms a foundation for insight of their predecessors who derived so muchfurther progress and suggests roads to even higher fundamental knowledge with the primitive and evengoals than we have thus far reached. It is truly said erratic equipment at their disposal. It is truly remark-that we of today stand on the shoulders of giants. able that they wrested such great wisdom from such

To help us use the past to inspire us to future limited resources. If the story of their ability can con-achievement, the authors of this article give us a tinue to guide and encourage the scientist and the en-thrilling trip in what might be termed a "technological gineer, then the future promises ever-greater accom-time machine." Hopefully we shall all benefit from the plishments for the service of mankind.lessons set forth, from the examples of Galvani and A. N. GoldsmithVolta, of Nobili and Matteucci. We of the space age, Director Emeritus, IEEE

IIFFE spectruill DF.CE%IFR 1971

Although almost everyone has heard of Galvani and ability to activate muscles and nerves, it is readily under-Volta-whose names have entered the English language in standable that biologists began to suspect that the "ner-such words as galvanize and volt-surprisingly few have an vous fluid" or the "animal spirit" postulated by Galenaccurate knowledge of the experiments they performed, to course in the hollow cavities of the nerves and mediatethe conclusions they drew therefrom, and the profound muscular contraction, and indeed all the nervous func-manner in which their studies influenced science within tions, was of an electrical nature. Galvani, an obstetricianonly a few years. There is no doubt that the chance ob- and anatomist, was by no means the first to hold such aservation by Galvani, the three experiments that he con- view, but his experimental search for evidence of theducted, and the controversy that ensued with Volta were identity of the electric and nervous fluids provided theat the basis ofthe discovery of all bioelectric phenomenons critical breakthrough. During the first of his experiments,as well as of current electricity, despite the fact that Gal- conducted in his home, he noted that every time a sparkvani's explanation for his experiment was wrong and was drawn from a nearby static-electricity machine whileVolta was not altogether correct in the theory he pre- an assistant was touching the sciatic nerve trunk of asented for the operation ofthe battery he devised. Because frog with the point of a scalpel, the leg muscles twitched.of the importance of these events, the authors have sought Green's translation2 of Galvani's account follows:to present the evidence to the reader by recounting the "I dissected and prepared a frog [as in Fig. 1] andGalvani-Volta story in a simple way, using quotations placed it on a table, on which was an electrical machine...drawn directly from Galvani's and Volta's reports. In widely removed from its conductor and separated by noaddition, the phenomenons they discovered are analyzed brief interval [distance]. When by chance one of thosein the light of present-day knowledge. who were assisting me gently touched the point ofa scalpelThe critical events of this history took place in the to the medial crural nerves, DD, of this frog, imme-

decade just prior to 1800. Before this time there had ac- diately all the muscles of the limbs seemed to be so con-cumulated a considerable inventory of facts relating to tracted that they appeared to have fallen into violent tonicbioelectricity and electricity in general. The Egyptians convulsions. But another of the assistants, who was onand Greeks had known that certain fish could deliver hand when I did electrical experiments, seemed to ob-substantial shocks to an organism in their aqueous serve that the same thing occurred whenever a spark wasenvironment.' It was also known that the application of discharged from the conductor of the machine. .."generators of static electricity would cause muscles to After some additional experiments to authenticate thetwitch by stimulating the muscle or its nerve directly. phenomenon, Galvani wrote:Well before the dawn of Christianity, static electricity "Aroused by the novelty of the circumstance, we re-had been discovered by the Greeks, who produced it by solved to test it in various ways, and to experiment, em-rubbing resin (amber or, in Greek, elektron) with. cat's ploying nevertheless the same scalpel, in order that, iffur. Later it was found that static electricity could be possible, we might ascertain the causes of the unexpectedcreated by rubbing glass with silk. It was thought that difference; nor did this new labor prove vain; for wedifferent types of electric "fluid" were produced by these found that the whole thing was to be attributed to thetwo methods; consequently the adjectives "resinous" and different part of the scalpel by which we held it with our"vitreous" were applied. It was also common knowledge fingers: for since the scalpel had a bone handle, when thethat a substantial quantity of electric fluid could be pro- same handle was held by the hand, even though a sparkduced by frictional electric machines, the first of which was produced, no movements resulted, but they did ensue,appears to have been developed by Von Guericke about if the fingers touched either the metallic blade or the iron1672. In 1747 Van Muschenbroek and Von Kleist inde- nails securing the blade of the scalpel."pendently discovered that electric fluid could be stored in It is clear from this report that Galvani didn't demon-a Leyden jar, the precursor of the capacitor. strate the existence of bioelectricity; stimulation of theAbout this time Franklin had become interested in crural (sciatic) nerve occurred by electrostatic induction

electricity and he performed experiments that led to the in the circuit between the static-electricity machine, the"one-fluid theory," which stated that there was but one frog preparation, the observer, and earth. Nonetheless,type of electricity and that the electrical effects produced the experience prompted him to wonder if atmosphericby friction reflected the separation of electric fluid so that electricity would produce a similar response. His nextone body contained an excess, the other a deficit. (It is experiment was designed to test this hypothesis. Theinteresting to note that the "unit of electric fluid," the various translations of Galvani's second experiment agreeelectron, was not discovered until more than a century in overall, but not fine, detail; Green's translation2 states:later.) Franklin also showed that atmospheric electricity "Having discovered the effects of artificial electricity on(lightning) and artificial electricity, derived from electric muscular contractions which we have thus far explained,machines, were one and the same. By this time Coulomb there was nothing we would sooner do than to investigatehad performed his experiments and enunciated his inverse- whether atmospheric electricity, as it is called, would af-square law for the force of attraction or repulsion between ford the same phenomena, or not: whether, for example,charged bodies. Despite this array of discoveries, it is by employing the same devices, the passage of lightning,important to note that before the time of Galvani and as of sparks, would excite muscular contractions.Volta, there was no source that could deliver a continuous "Therefore we erected, in the fresh air, in a lofty part offlow of electric fluid, a term that implies both charge and the house, a long and suitable conductor, namely an irroncurrent. wire, and insulated it [Fig. 2] and to it, when a storm arose

in the sky, attached by their nerves either prepared frogs,Galvani's experiments or prepared legs of warm animals .............. Also we attached

Against such a background of knowledge of the "elec- another conductor, namely another iron wire, to the feet oftric fluid" and the many powerful demonstrations of its the same, and this as long as possible, that it might extend

Geddes, Hoff-The discovery of bioelectricity and current electricity

as far as the waters of the well indicated in the figure. dry; nothing similar occurred; it was not possible toMoreover, the thing went according to our desire, just as observe any muscular motions or contractions. Results ofin artificial electricity; for as often as the lightning broke this sort both brought us no slight amazement and beganout, at the same moment of time all the muscles fell into to arouse some suspicion about inherent animal electricityviolent and multiple contractions, so that, just as the itself. Moreover both were increased by the circuit of verysplendor and flash of the lightning are wont, so the thin nervous fluid which by chance we observed to be pro-muscular motions and contractions of those animals pre- duced from the nerves to the muscles, when the phe-ceded the thunders, and, as it were, warned of them; nay, nomenon occurred, and which resembled the electricindeed, so great was the concurrence of the phenomena circuit which is discharged in the Leyden jar."that the contractions occurred both when no muscle con- Figure 3 illustrates a variety of Galvani's experimentsductor was also added, and when the nerve conductor was in which a bimetallic arc is used to connect the spinalnot insulated, nay it was even possible to observe them marrow to the leg muscles. Although Galvani noted thatbeyond hope and expectation when the conductor was the "contractions were different in accordance with theplaced on lower ground particularly if the light- diversity of the metals," he reasoned that by connectingnings either were very great, or burst from clouds nearer the nerve and the muscle by the metallic arc (armature)the place of experimentation, or if anyone held the iron consisting of two dissimilar metals, he had discharged thewire F in his hands at the same time when the thunder- animal electricity present in the muscle, thinking that thebolts fell." nerve and muscle were analogous to the inner and outer

In the course of these experiments, Galvani noted an- conductors of a Leyden jar. It was Galvani's failure toother phenomenon, which, according to Green,2 he re- realize that a conducting arc of two dissimilar metals wasported as follows. This observation has become known essential for contractions that later led Volta to find aas Galvani's second experiment. very different explanation for the phenomenon.

"Wherefore, since I had sometimes seen prepared frogs (It is of interest to note that a new English translation ofplaced on iron gratings which surrounded a certain Galvani's De Viribus Electricitatis is available, with an in-hanging garden of my house, equipped also with bronze troduction by Cohen of Harvard and a revised biblio-[some accounts refer to copper or brass] hooks in their graphy by Fulton and Stanton of Yale.3 See also Ref. 4.)spinal cord, fall into the customary contractions, not onlywhen the sky was lightning but also sometimes when it Volta's explanationwas quiet and serene, I thought these contractions derived Galvani's investigations aroused a virtual furor oftheir origin from the changes which sometimes occur in interest. Wherever frogs were to be found, scientists andatmospheric electricity. Hence, not without hope, I began laymen alike repeated his experiments with routinediligently to investigate the effects of these changes in success. Dibner4reports that Galvani's second experimentthese muscular motions in various ways. Wherefore at was performed at social gatherings and Galvani's explana-different hours, and for many days, I inspected animals, tion for the muscular contractions (discharge of a nerve-appropriately adjusted therefor; but there was scarcely muscle Leyden jar) was accepted without question-evenany motion in their muscles. Finally, weary with vain ex- by Volta, who had received a copy of Galvani's paper andpectation I began to press the bronze hooks, whereby verified the phenomenon. However, Volta very soon hadtheir spinal cords were fixed, against the iron gratings, to second thoughts on the subject and found that the essen-see whether by this kind of device they excited muscular tial requirement for producing contractions was the pres-contractions, and in various states of the atmosphere, and ence of two dissimilar metals joined at one end, with theirof electricity whatever variety and mutation they pre- free ends applied to either the nerve or muscle. If a singlesented; not infrequently, indeed, I observed contractions, metal was applied to the nerve and muscle, no contrac-but bearing no relation to varied state of stmosphere or tions were obtained. Volta immediately described hisof electricity. findings in letters to various learned societies. (The ex-

"Nevertheless, since I had not inspected these contrac- periments conducted by Galvani and Volta were reportedtions except in the fresh air, for I had not yet experi- in letters and scientific publications.5'6) Of the variousmented in other places, I was on the point of seeking such translations published, that which appeared in 1793 incontractions from electricity of the atmosphere, which the Transactions of the Royal Society-of which Voltahad crept into the animal and accumulated in him and was a foreign member-is perhaps one of the more in-gone out rapidly from him in contact of the hook with the teresting. The report was the content of a letter fromiron grating; for it is easy in experimentation to be Volta to Tiberius Cavallo7:deceived, and to think one has seen and discovered what "But if he [meaning Galvani] had but a little morewe desire to see and discover. varied the experiments, as I have done, says Mr. Volta, he"But when I had transported the animal into a closed would have seen that this double contact of the nerve and

chamber and placed him on an iron surface, and had be- muscle, this imaginary circuit, is not always necessary.gun to press against it the hook fixed in his spinal cord, be- He would have found, as I have done, that we can excitehold the same contractions and the same motions! Like- the same convulsions and motion in the legs, and thewise continuously, I tried using other metals, in other other members of animals, by metallic touchings, either ofplaces, other hours and days; and the same result; except 2 parts of a nerve only, or of 2 muscles, and even of differ-that the contractions were different in accordance with ent points of one simple muscle alone."the diversity of metals, namely more violent in some, and Following a discussion of various complementary ex-more sluggish in others. Then it continually occurred to periments, the report continues:me to employ for the same experiment other bodies, but "Yes it is a quite different sort of method of electricthose which transmit little or no electricity, glass for fluid, of which we ought rather to say we disturb theexample, gum, resin, stone, wood, and those which are equilibrium, than restore it, in that which flows from one

40) IEEE spectrum DECEMBER 1971

S~~~~~~~~~~~~~~~~~~~~~~~~---a _ BC 5_~~~~~~~~~~~~~~~~Ged, Hol Th dicvr fbolcrct ti uritcetiiv4

part to another of a nerve, or muscle, etc. as well as place is it not capable of giving every moment shocks ofinteriorly by their conducting fibers as exteriorly by greater or less strength, according to circumstances-means of metallic conductors, not a consequence of a shocks which are renewed by each new touch, and which,respective excess or defect, but by action proper to these when thus repeated or continued for a certain time, pro-metals when they are of different kinds. It is thus, says duce the same torpor in the limbs as is occasioned byMr. Volta, that I have discovered a new law, which is not the torpedo etc. ?'so much a law of animal electricity, as a law of common Volta soon found that evaporation of the electrolyteelectricity; to which ought to be attributed most of the weakened the strength of the pile. In the same paper, hephenomena, which would appear, from Galvani's experi- described the predecessor to the wet battery, which hements and mine, to belong to a true spontaneous animal characterized as a "crown of cups" (couronne de tasses)electricity, and which is not so; but are really the effects of and which produced a stronger and longer-lasting electrica very weak artificial electricity. As to the motion of the force. (The Royal Society translator used the term "chainmuscles, my experiments, varied in all possible ways, of cups.") Volta's account8 follows. Note that he used Sshow that the motion of the electric fluid, excited in the and Z as the symbols for silver and zinc.organs, does not act immediately on the muscles; that it "I dispose, therefore, a row of several basons [basins]only excites the nerves, and that these, put in motion, or cups [Fig. 4] of any matter [material] whatever, exceptexcite in turn the muscles." metal, such as wood, shell, earth, or rather glass (small

Volta believed that the source of potential that stim- tumblers or drinking glasses are the most convenient),ulated the spinal nerves (and which could be shown to half filled with pure water, or rather salt water or ley: theyevoke sensation by placing a copper coin above and a are made to communicate by forming them into a sort ofsilver coin below the tongue and bringing the edges of the chain, by means of so many metallic arcs, one arm ofcoins together) was the "mere mutual contact of different which, Sa, or only the extremity S, immersed in one ofkinds of metal, and even by that of other conductors, also the tumblers, is copper or brass, or rather of copperdifferent from each other either liquid or containing plated with silver; and the other, Za, immersed into thesome liquid, to which they are properly indebted for their next tumbler is of tin, or rather zinc. I shall here observe,conducting power."8 Despite the belief that only dissimilar that ley and other alkaline liquors are preferable when onemetals were required he was unsuccessful in producing of the metals to be immersed is tin: salt.water is preferableelectricity with a stack of coins of two different metals. when it is zinc. The two metals of which each arc is com-Finally succeeding with a pile that consisted of both dis- posed, are soldered together in any part above that whichsimilar metals and an electrolyte, he wrote8: is immersed in the liquor, and which must touch it with a"The apparatus to which I allude [Fig. 4] and which will, surface sufficiently large: It is necessary therefore that this

no doubt astonish you, is only the assemblage of a number part should be a plate of an inch square, or very littleof good conductors of different kinds arranged in a cer- less; the rest of the arc may be much narrower as youtain manner. Thirty, forty or more pieces of copper, or choose, and even a simple metallic wire. It may alsorather silver, applied each to a piece of tin, or zinc, which consist of a third metal different from the two immersedis much better, and as many strata of water or any other in the tumblers, since the action on the electric fluidliquid which may be a better conductor, such as salt water, which results from all the contacts of several metals thatley [lye], etc., or pieces of pasteboard skin etc. well soaked immediately succeed each other . . .in the liquids; such strata are interposed between every "A series of 30, 40 or 60 of these tumblers connectedpair or combination of two different metals in an alternate with each other in this manner, and ranged either in aseries, and always in the same order of these three kinds straight or curved line, or bent in every manner possible,of conductors are all that is necessary for constituting my forms the whole of this new apparatus, which at bottomnew instrument, which as I have said, imitates the effect of and in substance is the same as the columnar one [thethe Leyden flask, or of electric batteries by communicat- pile] above described; as the essential part, which con-ing the same shock as these do; but which indeed is far sists in the immediate communication of the differentinferior to the activity of these batteries when highly metals which from each couple and the mediate communi-charged, either in regard to the force and noise of the cation of one couple with the other, viz. by the inter-explosions, the spark, the distance at which the discharge vention of a humid conductor exist in the one as well asmay be affected, etc. as it equals only the effect of a battery the other."very weakly charged, though of immense capacity: in Considerable time was to pass before true explanationsother respects, however it surpasses the virtue and power became available for what Galvani and Volta had done.of these batteries as it has no need, like these, of being Clearly, both had demonstrated the existence of a differ-previously charged by means of foreign electricity, and as ence of electric potential-but what produced it eludedit is capable of giving a shock every time it is properly Galvani, and even Volta. We now can identify the poten-touched, however often it may be. tial difference present in the experiments carried out by"To this apparatus, much more familiar at bottom, as both investigators. Although Galvani thought that he

I shall show, and even such as I have constructed it, in its had initiated muscular contractions by dischargingform to the natural electric organ of the torpedo or electric animal electricity resident in a physiological capacitoreel, etc. than to the Leyden flask and electric batteries, consisting of the nerve (inner conductor) and muscleI would with to give the name the artificial electric organ surface (outer conductor), as diagrammed in Fig. 5A, weand, indeed, is it not like it, composed entirely of conduct- now know that the stimulus was derived from the electro-ing bodies? Is it not also active of itself without any motive force that exists at an electrode-electrolyte inter-previous charge, without the aid of any electricity by face; this voltage is designated the half-cell potential.any of the means hitherto known? Does it not act in- It was Nernst9 who carried out the fundamental theo-cessantly, and without intermission? And in the last retical s-tudies that ultimately led to the measurement of

42 IEEE spectrum DECEMBER 1971

FIGURE 4. Volta's pile (Figs. 2, 3, and 4) and crown of cups (Fig. 1). (From Ref. 7, by permission)

half-cell potentials; their practical measurement was Figure 5A illustrates what Galvani thought he didmade possible by Hilderbrand's introduction' of the (discharge a nerve-muscle Leyden jar) and Fig. 5Bstandard hydrogen electrode (SHE). Electrode potentials, illustrates what he actually did-stimulate the nerve withmeasured with respect to the SHE, are found in a variety a voltage composed of two half-cell potentials (EA, EB).of tests on electrochemistry. It is pertinent to note that Equating the tissue fluids of the frog to an 0.6 percentthe half-cell potential of an electrode depends on, the saline solution, the potential difference between iron andtype of metal, and to a lesser degree on the concentration copper electrodes was measured and found to be 450 mV;and temperature, of the electrolyte in which it is placed. essentially the same voltage was obtained from anThe potential difference of a galvanic or voltaic cell, con- iron-brass cell. Since stimulation of a nerve merelysisting of two dissimilar metals in an electrolyte of unit requires a small reduction (perhaps 30 mV) in the mem-activity, is the difference between the half-cell potentials brane potential, the voltage available from the iron-of the two electrodes. copper or iron-brass cell is ample for stimulation,With the foregoing information as background, it is even though it is not applied across cell membranes.

possible to estimate the approximate magnitude of the Volta also noted that the strength of the pile or crownpotential differences encountered by Galvani and Volta. of cups-as judged by an electrometer or the size of the

Geddes, Hoff-The discovery of bioclectricity and current electricity

spark or the shock perceived on touching the ends- instant practical use to provide a sustained flow ofdepended on a difference in the types of metals employed current. Dibner4 reports that Davy, for example, at theto construct the battery. (The magnetic field surrounding Royal Institution, constructed a battery consisting ofa current-carrying conductor, which is the basis of 500 cells for his studies on the electrolytic decompositionoperation of the "galvanometer," was not discovered ofchemical compounds.until 1820 by Oersted, I I who had considerable difficulty in Volta's conclusive demonstration that Galvani had notgetting his paper published.) In a single cell of the pile or discovered animal electricity was a blow from which thechain, he preferred silver to copper or brass for one latter never recovered. Perhaps because of the death ofelectrode; for the other, zinc was preferable to tin. For his beloved wife, who assisted him in his experiments,a silver-zinc cell (assuming an electrolyte of unit activity), and possibly also because of the troubled times in Italythe potential difference is 1.56 volts; for a copper-zinc resulting from Napoleon's empire-building activities,cell, it is 1.10 volts. Volta also noted that for the electro- little more was heard directly from Galvani. Nevertheless,lyte, lye was better than salt water, which was better than he persisted in his belief in animal electricity and con-"4ordinary" water. It is interesting to note that the ducted his third experiment, which definitely proved themodern silver-zinc battery has the highest open-circuit existence of bioelectricity. In this experiment, he heldvoltage (1.86) of any of the commercially available cells, one foot of the frog nerve-muscle preparation andwith the exception of the lead-acid cell. swung it so that the vertebral column and the sciatic

Volta also found that in a series arrangement of cells, nerve touched the muscles of the other leg. When thisthe use of a connecting wire of a different metal than occurred, or when the vertebral column was made to fallthose used for each cell had virtually no effect on the on the thigh, the muscles contracted vigorously. Ac-strength of the battery. He wrote: "It [the connecting cording to most historians, it was his nephew Aldini whowire] may also consist of a third metal different from the championed Galvani's cause by describing this importanttwo immersed in the tumblers [containing the electrolyte] experiment, in which he probably collaborated. Thesince the action on the electric fluid which results from all experiment conclusively showed that muscular contrac-the contacts of several metals that immediately succeed tions could be evoked without metallic conductors.each other, or the force with which this fluid is at last According to Fulton and Cushing,5 Aldini wrote:impelled, is absolutely the same, or nearly so, as that "Some philosophers indeed, had conceived the idea ofwhich it would have received by the immediate contact producing contractions in a frog without metals; andof the first metal with the last, without any intermediate ingenious methods, proposed by my uncle Galvani,metals, as I have ascertained by direct experiments, of induced me to pay attention to the subject, in order thatwhich I shall have occasion to speak hereafter." I might attain to greater simplicity. He made me sensible

It is curious to note that Volta repeatedly ascribed the of the importance of the experiment and therefore I wassource of electromotive force in his pile and crown of long ago inspired with a desire of discovering thatcups to the contact between dissimilar metals: "The interesting process. It will be seen in the Opuscoli ofelectric fluid which results from all the contacts of several Milan (No. 21), that I showed publicly, to the Institute ofmetals that immediately succeed each other."...""My Bologna, contractions in a frog without the aid of metalsexperiments on electricity excited by the mere mutual so far back as the year 1794. The experiment, as describedcontact of different kinds of metal . . . ." Probably this in a memoir addressed to M. Amorotti [sic] is as follows:explanation was derived from experiments in which he I immersed a prepared frog in a strong solution ofevoked a sensation of taste, which he experienced by muriate of soda. I then took it from the solution, and,placing a copper and a silver coin on either side of his holding one extremity of it in my hand, I suffered thetongue and bringing their edges together. other to hang freely down. While in this situation, I

Despite the inaccuracy in Volta's explanation for the raised up the nerves with a small glass rod, in such aoperation of the electrolytic cell, it nonetheless was put to manner that they did not touch the muscles. I then

suddenly removed the glass rod, and every time that thespinal marrow and nerves touched the muscular parts,contractions were excited. Any idea of a stimulus arisingeither from the action of the salt, or from the impulse

FIGURE 5. Galvani's explanation for the production of produced by the fall of the nerves, may be easily removed.muscular contraction was based on the Leyden jar (ca- Nothing wil be necessary but to apply the same nervespacitor) analogy (A). He had, in fact, stimulated the nerve-muscle preparation (B) by the voltage developed by the to the muscles of another prepared frog, not in a Galvanictwo half-cells. circle; for, in this case, neither the salt, nor the impulse

Nerve even if more violent, will produce muscular motion."Nerve 1

Cu Nobili's frog currentCu Because this demonstration of animal electricity was

I < / ~~~~~~~~~~~soremarkable, it is important to analyze the reason for. _____\ / \ / ~~~~Feits success. We now know that even a slight injury to

____/ /~Mucl living cells causes the injured area to be negative with/Fe Muce 2 respect to uninjured regions; the potential difference/ \ 2 ~~~~~~~~~~betweeninjured and intact tissue is called the injury

/ \/ ~~~~~~~~~~potentialand can amount to some 50 mV. Thus, appli-1/ ~~~~EAEB cation of a nerve to a muscle having intact and uninjured

: 1 W Muscle 1-fl-| 2 areas will cause the injury potential to act as a stimulusI A B CuINaCI Fe/NaCI large enough to stimulate an excitable nerve. That such

IEEE spectrum DECEMBER 1971

an injury potential does exist, and can stimulate, was was able to construct an electric detector that approached,proved by Nobili.'2 He placed a skinned, decapitated though it did not equal, the galvanoscopic frog infrog so that its feet dipped into one glass of water or sensitivity. He accepted fully the evidence of the con-saline solution and its trunk into another, and he con- tractions of the frog as proof that the frog current didnected the fluid in the two glasses by a cotton or asbestos exist. Reasoning that it must arise from conductorsthread soaked in the solution. No metals entered the "enough different from each other to make an appreciableconducting arc; nevertheless, the frog muscles contracted current in the frog," he added, "we shall often have thewhen the connection was made. Nobili at once recognized occasion to talk of this current, we shall call it for thisthe response as the "galvanic contraction without reason, courant de la grenouille, without bothering aboutmetals," and he accepted its origin as the result of self- the regions, whatever they are, that produce it." 12stimulation of the frog by its own intrinsic electricity-the courant de la grenouille. He wrote: Matteucci's contribution"Having recognized the frog current so promptly, my Although Galvani's and Volta's original explanations

first thought was to introduce a similar current in one of for their experiments were only partially correct, it isthe most sensitive of my multipliers* [galvanometers], to certainly true that Volta discovered the means wherebyobserve the indications it would give. I had such con- electric energy could be derived from chemical energyfidence in the instrument that I employed, that I was and that Galvani, by his third experiment on contractionsgreatly astonished to see that the frog still contracted in produced without metals, proved the existence of athe new circuit while the needle of the multiplier showed bioelectric potential. The subsequent history of currentnot the least movement. This result made me fear that electricity is well known; less familiar, however, is thethe instrument was not capable of measuring the currents story of bioelectricity and its close association with andproduced by conductors of the second class [electrolytes], dependence on developments in the physical sciences.but before giving too much weight to this opinion I made To summarize this story briefly, the next great contribu-a second attempt. I constructed another galvanometer, tion to the field was made by Galvani's countryman,to which I gave all my attention so that it would succeed Carlo Matteucci, who both confirmed Galvani's thirdbetter than the preceding ones. It was in fact much more experiment and made a new discovery, that of the actiondelicate, and I had indisputable signs of the frog current. potential that precedes the contraction of skeletal muscle.The glasses being filled with common water, the devi- In confirming Galvani's third experiment, which demon-ations were of a few degrees; but with the saline solution strated the injury potential, Matteuccill noted, "I injurethe first movements of the needle were of 10, 200, and the muscles of any living animal whatever, and into theeven 300. The current of the frog goes from the muscles interior of the wound I insert the nerve of the leg, whichto the nerves, that is to say, from the feet to the head. I hold, insulated with glass tube. As I move this nervousWhile frogs contract under the action of their intrinsic filament in the interior of the wound, I see immediatelycurrent only for a short time, the galvanometer shows strong contractions in the leg. To always obtain them,signs of it for hours." it is necessary that one point of the nervous filamentEven though the galvanometer could indeed detect the touches the depths of the wound, and that another point

frog current, Nobili found that a current too feeble tomove the galvanometer would nevertheless evoke con-tractions in a frog. Studying the frog current somewhatfurther-and it was more or less incidental to his com-parison of the physical with the physiological galva- FIGURE 6. Demonstration of the injury and discovery ofnometer-Nobili noted, 12 "The frog current has a certain the action potential as shown by Matteucci's two mostdirection and a certain force, and one may destroy it by important experiments. A-The injury potential, which

directing itaao. Ir o exists between an intact and an injured (cut) area, stim-directing it against another of equal intensity. If one ulates a nerve when it bridges the two regions; this isprepares two frogs in the usual manner, and forms a indicated by a twitch in the muscle innervated. B-galvanic circuit with them alone, by placing in reciprocal Stimulation of nerve N, causes muscle Ml to contractcontact the nerve of one with the muscle of the other, and its accompanying action potential stimulates nerveboth frogs contract; they remain motionless on the N2 as revealed by contraction in muscle M2.contrary, when one reverses the disposition of contacts, Nervetouching the nerve with the nerve, and the muscle withthe muscle."

Following the reasoning suggested by these observa-tions, he arranged frog preparations in series, placing thetrunk of the second on the legs of the first, and so on, tomake a "voltaic pile" of frogs, and observed an increase Musclein the deflection of the multiplier.

Nobili thus may be credited with the first demonstra- Cut muscletion by physical instruments of the existence of the Abioelectric current that today we recognize as injurycurrent. However, he made no special point of this B |Stimulus Mdemonstration apart from the fact that it showed that he N

The term "multiplier" was used for any device that increased(e.g., multiplied) the Oersted effect; the magnetic field surrounding Ma current-carrying conductor.

Geddes, Hoff-The discovery of bioelectricity and current electricity 45

of the same nerve touches the edge of the wound." philosophy in the University of Pavia, to Mr. Tiberius Cavaio,(See Fig. 6A.) F.R.S.," Phil. Trans. Roy. Soc. London, vol. 83, pp. 285-291,(See Fig. 6A.) ~~~~~~~~~~~~1793.By using a galvanometer, Matteucci found that the 8. Volta, A., "On the electricity excited by the mere contact of

difference of potential between an injured and uninjured conducting substances of different kinds. In a letter from Mr.area was diminished during a tetanic contraction; study Alexander Volta, F.R.S.. professor of natural philosophy in theareawas ~~ ~ ~ ~ ~ ~~~~Su University of Pavia, to the Rt. Hon. Sir Joseph Banks, Bart.of this phenomenon was to occupy the attention of all K.B.P.R.S." Phil. Trans. Roy. Soc. London, vol. 90, pp. 744-746,succeeding electrophysiologists. More than this, how- 1800.ever, Matteucci made another remarkable discovery- 9. Nernst, W., "Die elektromotorische Wirksamkeit der Jonen,"r Z. Physik. Chem., vol. 4, pp. 129-188, 1889.that accompanying a contraction of intact skeletal 10. Hilderbrand, J. H., "Some applications of the hydrogenmuscle there occurs a transient bioelectric event, now electrode in analyses research and teaching," J. Am. Chem. Soc.,designated the action potential. He demonstrated this by vol. 35, pp. 847-871, 1913.showing that a contracting muscle is able to stimulate a 11. Oersted, J. D., in J. Chem. Phys., vol. 56, p. 394, 1820; alsoin La Decouverte de 'Electromagnetisme Faite en 1820 par J-C.nerve that, in turn, causes contraction of the muscle Oersted. Copenhagen: Larsen, 1820.innervated by it. Matteucciu4 explained: 12. Nobili, C. L., "Comparison entre les deux galvanometres

"I place upon an insulated surface ofwaxed or varnished les plus sensibles, la grenouille et le multiplicateur a deux aiguilles,suivie de quelques resultats nouveaux," Aim. Chim. Phys., vol. 38,cloth a frog, prepared in the ordinary manner; then I pp. 225-245, 1828.

prepare another frog so as to have only a leg with thenervous fillet or fascicle which comes from the marrowto the muscles of the leg. It is necessary to have care, not Reprints of this article (X71-123) are available to readers.to be led into error, to remove all the muscles of the Please use the order form on page 8, which gives infor-thigh, and that the nervous filament be thoroughly mation and prices.denuded."Then I place the nervous filament upon the thighs of

the first frog, in such a way that the filaments of the leg Leslie A. Geddes (SM)touched by the nervous filament do not come in contact is professor of physiologywith the thighs, and so that this filament is not under 4A_ and chief of the Divisiontension.... When one touches with a voltaic couple the of Biomedical Engineer.lumbar nerves of the frog, at that instant the muscles of ing at Baylor College ofMedicine, Houston, Tex.,the thighs contract; at the same time, one sees the leg and assistant professorcontract, whose nerve is resting upon the muscles set of physiology at the Uni-into contraction." Figure 6B shows the equipment. versity of Texas DentalThrough the simple experiments of Galvani, Nobili, College in Houston. He

and Matteucci, the existence of a bioelectric potential also is professor of phys-was established; its transient disappearance during erinary Medicine (Grad-activity in skeletal muscle, a recording of which later uate School), and professor of biomedical engineer-became known as the action potential, was Matteucci's ing, Faculty of Engineering, at Texas A&M Universitymnajor contribution. Soon thereafter the presence of an and serves as a consultant to the National Insti-action potential was discovered in cardiac muscle and tion. Born in Scotland and educated in Canada,nerve. Measurement of its temporal nature was accom- Dr. Geddes received the B.E. and M.E. degreespUshed by a remarkably simple instrument, the rheotome. in electrical engineering from McGill UniversityWith this device it was possible to use-galvanometers and the Ph.D. degree in physiology from thethat had response times far too long for the events they Baylor College of Medicine. He has publishedprolifically, is a member of many scientific andmeasured and, by utilMng what is now known as sam- professional societies, and is currently a consultingpling theory, to obtain accurate voltage-time graphs editor to a number of periodicals, including thecovering only milliseconds. However, the story of these IEEE Transactions on Blo-Medical Engineering.triumphs of instrumentation in the measurement of HebbelLe Hoff is associ-short-duration bioelectric events will be reserved for a ate dean for faculty andfuture account. clinical affairs, Benjamin

F. Hambleton prof-essorREFERENCES of physiology, and chair-I. Kellaway, P. E. C., "The part played by electric fish in the mnof thesooyDeaylrtmentearly history of bioelectricity and electrotherapy," Bull. Hist. of Physiology, Baylor ColMed., vol. 20, pp. 112-137, 1946. lege of Medicine, Hous-2. Galvani L., Commentary on the Effect of Electricity on Mus- ton, Tex. He is alsocular Motion (translated by R. M. Green). New Haven, Conn.: visiting professor, Depart-Licht, 1953. ment of Physiology, Uni-3. Galvani, L., De Viribus Electricitatis (in English). Norwalk, versity of Texas DentalConn.: Burndy Library, 1953. Branch, and a consultant4. Dibner, B., Galvani-Volta: A Controversy That Led to the to the Veterans' Administration Hospital, both inDiscover*i of Useful Electricity. Norwalk, Conn.: Burndy Houston. Dr. Hoff holds the B.S. degree from theLibrary, 1952. University of Washington, the B.A., M.A., and Ph.D.5. Fulton, J. F., and Cushing, H., "A bibliographical study of thc degrees from Oxford University, and the M.D.Galvani and Aldini writings on animal electricity," Ann. Sci., degree from Harvard University. He received thevol. 1, pp. 239-268, 1936. Distinguished Service Professor Award from the6. Hoff, H. E., "Galvani and the pre-Galvani electrophysiolo- Baylor College of Medicine in 1968. His major re-gists," Ann. Sci., vol. 1, pp. 157-172,1936. search interest is the physiology of the cardiovas-7. Volta, A., "Account of some discoveries made by Mr. Galvani cular-respiratory system and he has published moreof Bologna with experiments and observations on them. In two than 350 scientific papers.letters from Mr. Alexander Volta, F.R.S., professor of natural

Geddes, Hoff-The discovery of bioelectricity and current electricity