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THE 
 
 EXPERIMENTAL METHOD 
 
 MEDICAL SCIENCE 
 
 SECOND COURSE OF THE CARTWRIGHT LECTURES OF THE 
 
 ALUMNI ASSOCIATION, COLLEGE OF PHYSICIANS 
 
 AND SURGEONS, NEW YORK 
 
 DEUVERBD 
 
 Janvary 24, January 31, and February 7, 1882 
 
 JOHN C. DALTON, M.D. 
 
 NEW YORK 
 G. P. PUTNAM'S SONS 
 
 27 AND 29 WEST 23D STREET 
 1882 
 
<^^AJ.^, VU 
 
 //-K/ -30 
 
 Copyright, bv 
 G. P. PUTNAM'S SONS, 
 
 i332. 
 
 
CONTENTS. 
 
 LECTURE I. 
 
 FACE 
 
 Galvani and Galvanism in the Study of the Nervous 
 
 System i 
 
 LECTURE IL 
 Buffon and Bonnet in the Eighteenth Century , . . 39 
 
 LECTURE in. 
 
 Nervous Degenerations and the Theory of Sir Charles 
 
 Bell 72 
 
THE EXPERIMENTAL METHOD IN 
 MEDICAL SCIENCE. 
 
 LECTURE I. 
 
 GALVANI AND GALVANISM IN THE STUDY OF THE NERVOUS 
 
 SYSTEM. 
 
 Mr. President and Gentlemen of the Alumni, — In dis- 
 charging the agreeable duty which you have kindly im- 
 posed upon me, of giving- the Cartwright, Lectures for this 
 year, I propose to offer a few historical sketches, which 
 shall illustrate the manner in which certain parts of our 
 scientific knowledge in medicine have been attained. The 
 connection between scientific and practical medicine is 
 furthermore so close, that permanent improvement in the 
 one is inseparably dependent on that of the other; but 
 this connection becomes much more apparent when we 
 trace the history of any particular department for a con- 
 siderable period of time. By this means we can see how 
 much of the doctrine accepted by our predecessors has 
 survived the ordeal of a century, and what were the 
 methods of investigation which produced in their hands 
 the permanent results which we enjoy to-day. However 
 much we may pride ourselves on the advances made dur- 
 
2 GALVANI AND GALVANISM 
 
 ing our own time, we may be sure that by far the greater 
 part of our actual knowledge is a legacy from the past. 
 It has been winnowed in successive generations from the 
 errors and imperfections which always accompany its first 
 acquisition ; and it is probable that many of our own dis- 
 coveries will require a similar depleting treatment in the 
 future. But we may learn to rely with confidence on such 
 methods of study as have heretofore proved valuable ; and 
 we may, perhaps, save ourselves the trouble of exploring 
 certain paths, when we see that others have followed them 
 before, and have found that they lead nowhere. 
 
 If we can say that any one department in physiology, 
 pathology, and therapeutics, is now distinguished by a 
 special activity of investigation and growth, it is probably 
 that of the nervous system. A very large part of this 
 advance has been made by the application of electric 
 stimulus in determining the motor or sensitive properties 
 of different nerves, their influence on the heart and blood- 
 vessels, the localization of special centres in the brain and 
 spinal cord, or the diagnosis of morbid alterations in the 
 cerebro-spinal axis ; and the use of electricity in restoring 
 the power of movement or sensation when impaired by 
 disease is now acknowledged to be, in many cases, a most 
 serviceable means of cure. This has all come, directly or 
 indirectly, from the experiments of Galvani, nearly a hun- 
 dred years ago, on the nerves and muscles of the decapi- 
 tated frog. 
 
 In 1789 Galvani was professor of anatomy in the Uni- 
 versity of Bologna. In addition to the regular duties of 
 his professorial chair, he had made a number of valuable 
 investigations in comparative anatomy, such as those on 
 the structure of the kidneys and urinary ducts of birds, 
 and on the organ of hearing in the same class. Like 
 
IN THE STUDY OF THE NERVOUS SYSTEM. % 
 
 most of the scientific men of his day, he was also greatly 
 interested in the phenomena of electricity, which was 
 then fast developing into an important department of 
 physics. The condition of electrical science at that time 
 was as follows. The machine for producing frictional 
 electricity by a rotating glass cylinder and cushion had 
 been brought to practical completion, and was in common 
 use, with its prime conductor and insulating supports. 
 The two opposite kinds of electrical excitement, known 
 as vitreous and resinous, or positive and negative, were 
 fully recognized, as well as the distinction between con- 
 ductors and non-conductors ; and even some of the . 
 phenomena of induced electricity were known, though 
 explained in a manner somewhat different from that 
 which is now in vogue. Besides the electricaT machine, 
 experimenters were already in possession of the Leyden 
 jar, by which a large quantity of electricity may be stored 
 in a given space ; the electrophorus, by which a moderate 
 charge of electricity may be obtained at will from a per- 
 manent source ; several varieties of electrometers, or 
 electroscopes, for detecting the existence and amount of 
 slight electric disturbances ; and Volta's " condenser," in 
 which small quantities of electricity from a feeble source 
 might be accumulated, and made apparent by the elec- 
 trometer. Finally, Franklin had shown, by his daring ex- 
 periment with the kite in the thunder-storm, that the 
 lightning of the clouds was identical in its nature with 
 the spark from an electrical machine ; and this had largely 
 directed the attention of investigators to the study of at- 
 mospheric electricity, as compared with that produced 
 by artificial means. 
 
 Considering the long list of results which have followed 
 from Galvani's- early observations, the manner in which 
 
4 - GALVANI AND GALVANISM 
 
 they were first .made is a topic of much interest,' , He, 
 was in his laboratory,, engaged on experiments with the 
 electrical machine, and had,. lying upon the table near by, 
 a freshly dissected frog, prepared for some other purpose 
 in such a way that the denuded hjnd legs were connected 
 with the spinal, column by the crural nerves. . One of, his 
 assistants, accidentally touching, the nerves of the animal 
 with the -blade of a. scalpel, saw the legs convulsed ; and, 
 on watching more closely, it was seen that the contraction 
 occurred only at the moment of drawing, a spark from the 
 
 I conductor of the machine.- Once Galvani's attention at- 
 tracted, to so remarkable a phenomenon, his mind turned 
 
 'instantly to the investigation of its conditions^ -He 
 abandoned all other occupations, and seemed absorbed in 
 
 ! the attempt to detect its causes, and to learn, their mode 
 of operation. He determined, in the first place, that the 
 discharge of the conductor, arid the contact of the scalpel 
 with the frog's nerves, were both necessary ; for the mus- 
 cular contraction would not take place with either of them 
 alone. But, even when both conditions were present, 
 sometimes the muscles contracted, and sometimes they 
 did not. Puzzled by this variation, but still confident that 
 it must have a reasonable cause, he at last found .that it 
 depended on the way -the scalpel was held in the fingers. 
 
 f If .grasped by the end of its non-conducting ivory handle, 
 
 \there were no convulsions in the legs when the spark 
 was taken from the machine ; but if held in such a way 
 that the fingers touched the steel blade, or the rivets 
 which held it in place, the muscles were always, thrown 
 into action. The human body, therefore, served as a con- 
 
 " Aloysii Galvani de Viribus Electricitatis in Motu Musculari Commentarius. De 
 Bononiensi Scientiarum et Artium Instituto atque Academia Commentarii, 1791. 
 Tomus Septimus, p. 363. 
 
IN THE STUDY OF THE NERVOUS SYSTEM. 5 
 
 ductor ; and Galvani replaced it with success by an iron 
 wire,- which he attached by one extremity to the spinal 
 column, above the origin of the nerves, by a brass or 
 copper hook, leaving the other end in communcation with 
 the ground. Then he could dispense with the scalpel alto- 
 gether. He varied the contrivance in many ways, turning 
 Sometimes the attached and sometimes the free end of the 
 conductor toward . the electrical machine, increasing or 
 diminishing its length, and at last adding a second con- 
 ductor attached to the muscles of the leg. He took 
 especial pains to exclude the possibility of any direct 
 transfer of electricity from his machine to the dissected 
 frog, and yet convinced himself, by the aid of Volta's elec- 
 trometer, that in some way or other an electric discharge 
 passed through the frog, and was the exciting cause of its 
 convulsions. 
 
 These experiments were all performed with artificial 
 electricity obtained from the electrical machine. Galvani 
 then passed to his second series of observations, to se^ 
 whether a similar effect would be produced by atmospheric 
 electricity. On the approach of a thunder-storm, he 
 arranged one of the conducting wires so that its upper 
 extremity was in the open air, near the roof of his house, 
 and its lower extremity connected with the frog's spinal 
 column, while the other wire, attached to the muscles of 
 the leg, communicated below with the water in a well ; 
 and he then waited, like Franklin, for the discharge of a 
 thunder-cloud. The result followed as before, and every 
 peal was accompanied by a convulsive motion in the dis- 
 sected frog. He especially noticed that the convulsions 
 were simultaneous, not with the sound of the thunder, 
 but with the electric discharge; for, as he says, "the 
 muscular contractions and movements of the animal, like / 
 
6 GALVANI AND GALVANISM 
 
 the visible splendor of the lightning-flash, always preceded 
 the thunder-clap, and, as it were, gave notice that it was 
 coming." 
 
 So far Galvani had not really touched upon his final 
 discovery. The phenomena of muscular contraction in 
 these two sets of experiments were due, as we now know, 
 to the action of induced electricity. When he charged 
 the prime conductor of his electrical machine, or when 
 the thunder-cloud was passing over his house, an imper- 
 ceptible 'but real disturbance of the electric equilibrium 
 took place by induction in the wires attached to his dis- 
 sected frog ; and, when the original electrical tension ex- 
 pended itself in a discharge, there was a similar re-action 
 in his conducting wires, — a re-action which necessarily 
 passed through the nerves and muscles of the frog, and 
 threw it into convulsions. Galvani did not understand 
 this ; but he was engrossed with the idea of pursuing the 
 new fact which he had unexpectedly witnessed, and of fol- 
 lowing its investigation by whatever path might be open 
 to him. So it happened that he was led, in his third set 
 of experiments, to a result of far greater importance ; and 
 notwithstanding that the two former series had nothing to 
 do with this result, so far as the nature of their phe- 
 nomena were concerned, they were still the necessary and 
 perfectly natural preliminaries to its discovery. 
 
 Galvani knew that the violent disturbances of thunder 
 and lightning were not the only ones which take place in 
 the atmosphere, but that there were also other changes of 
 electrical condition going on more quietly in ordinary 
 weather. " After having tested," he says, " the action of 
 atmospheric electricity in thunder-storms, I was exceed- 
 ingly desirous of investigating it in its daily condition of 
 quietude and serenity." For this purpose he hung his 
 
IN THE STUDY OF THE NERVOUS SYSTEM. 7 
 
 freshly dissected frogs, by copper hooks attached to the 
 spinal column, from the iron railing of a balustrade about 
 his house, and left them there exposed to the sky. He 
 thought that perhaps the imperceptible exchange of elec- 
 tricity between the clouds and the atmosphere might be 
 betrayed by some movement in the frogs' limbs, and he 
 watched patiently with that object for several days ; but 
 there was not the least indication of muscular excitement. 
 At last, seeing that nothing further would come of the 
 experiment in that way, he shifted the position of the 
 limbs, and pressed them, still hanging by their hooks, 
 against the iron framework of the balustrade ; and instantly 
 a convulsion took place. He had niade a galvanic circuit. 
 The copper hook and the iron railing were the two metals 
 of the battery ; and, by bringing the muscles in contact 
 with the railing, he had completed the communication, 
 and had seen, for the first time, a muscular contraction 
 excited by the galvanic current. 
 
 But of course his knowledge of the real cause of the 
 contraction was still very incomplete ; and no one could 
 be more conscious of this than himself. He knew how 
 many sources of error there may be in drawing a conclu- 
 sion from visible facts, until they have been examined from 
 every direction. His most natural inference, if he had 
 remained satisfied with this experiment, would have been 
 that the electrical cause of the contractions came from 
 the atmosphere. " I was very much inclined," he says, 
 "to attribute these contractions to atmospheric electricity 
 which had accumulated in the frog, and was then suddenly 
 discharged by the contact of the hooks and railings, — never 
 having seen contractions produced in this way, except in 
 the open air, as I had not yet tried them in any other place, 
 — we may be so easily misled into thinking that we have 
 
8 GALVANI AND JGALVANISM 
 
 really seen whatever we hope or expect to see." But he 
 soon found that he could obtain the same results in his 
 closed laboratory as in the open air, at any time of the 
 day, in any weather, and under a great variety of con- 
 . ditions ; provided, only, that communication was made be- 
 tween the nerves and muscles by metallic conductors, with 
 no intervening non-conducting material. The best ar- 
 rangement was that in which the nerves were suspended 
 by copper hooks, or armed with tin-foil, while the denuded 
 feet of the frog rested on a silver plate, and the two were 
 then connected by a metallic arc. The human body, 
 1 being also a conductor^ might be interposed between the 
 lends of the arc without lessening, the result. < Galvani's 
 description of this part of the discovery is an interesting 
 episode, as it corroborates his proof of the .electric nature 
 of the force in operation. He found that if he held the 
 frog suspended by its copper hook in one hand, and 
 touched the silver plate with a metallic rod in the other, 
 Uhe frog was convulsed. Then he called in the assistance 
 of a colleague. "I was staying," he says, "at the countryT 
 house of the most noble and excellent Signor James Zam- 
 beccari, where Signor Rialpo of Spain, formerly a member 
 of the Society of Jesus, and a very learned man, was visit- 
 ing at the same time. He had already kindly aided me in 
 former experiments, and I begged him to do so again in 
 this instance. He accordingly took my place in holding 
 the frog, while, partly for convenience, and partly to 
 vary the conditions of the experiment, I myself: touched 
 the silver plate with my metallic rod; but, contrary to 
 expectation, no movement was produced." Then the two 
 I observers joined hands, and, on repeating the metallic 
 contact, found "to their delight" that communication 
 took place through the human electric chain,, and was 
 
IN THE STUDY OF THE NERVOUS SYSTEM. g 
 
 manifested by muscular contraction in the frog's leg. 
 From all these results the conclusion became irresistible, 
 that the convulsions previously observed in the frogs at- 
 tached to the iron railings were due to the contact of their 
 metallic supports. 
 
 It is perfectly evident that this third set of experiments 
 contained the substance of a new discovery, and Galvani 
 fully recognized the fact. In the two former series there 
 were external sources of electricity, either in the electrical 
 machine or in the thunder-clouds of the atmosphere. But 
 here all such conditions were excluded. There was noth- 
 ing to explain the phenomena but the frog's nerves and 
 muscles, and the metallic conductors between them. In 
 all Galvani's experiments his mind was forcibly impressed 
 by this fact, zind he was naturally led to suspect-that the 
 electricity which caused the convulsions might be derived 
 from the animal body itself. ' 
 
 He made many attempts to determine which of the two 
 kinds of electricity was produced in the nerves, and which 
 in the muscles ; thinking that one of these tissues would 
 naturally be positive and the other negative. But he' 
 finally considered the electricity to be distributed on the 
 exterior and in the interior of the muscle very much as it 
 is on the outer and inner surfaces of a Leyden jar. The 
 nerve, with its ramifications, leading from the interior of' 
 the muscle, he regarded as analogous to the chain and 
 knob of the Leyden jar ; and when it was connected by a 
 metallic arc with the exterior of the muscle, the animal 
 electric battery was discharged; and a convulsion ensued 
 from the stimulus of the shock. 
 
 In this way Galvani accounted for the phenomena wit- 
 nessed in his experiments. He was far from believing 
 that he fully understood all their relations ; but he was 
 
lO GALVANI AND GALVANISM 
 
 convinced of their importance, and had no doubt that 
 their obscurities would disappear on further investigation. 
 He especially noticed the advantage of uniting in the 
 armature of the limbs, or in the connecting arc, different 
 metallic substances. " There is an additional peculiarity," 
 he says, " which deserves attention, and which I have very 
 
 I often observed in regard to the connecting arcs ; namely, 
 that they are vastly more efficient when composed of dif- 
 
 'ferent metallic substances than when consisting of one 
 and the same metal." But he does not undertake to ex- 
 plain this peculiarity ; although he found, that, of various 
 metallic combinations, some were more effective than 
 others. 
 
 He was perfectly clear as to the prime importance of 
 what he had actually discovered, and the secondary value 
 of what was only inferential ; and this distinction is ex- 
 pressly stated in his opening chapter. " From all these 
 particulars," he says, "investigated and established by a 
 long series of experiments, we have not only shown that 
 these contractions are due to electricity, but have further- 
 more been able to indicate certain conditions and laws by 
 which they are regulated. . . . We have also appended to 
 the narrative a number of corollaries, together with some 
 additional conjectures and hypotheses, mainly in the hope 
 of opening a way for further experiments, by which we 
 may at leasf be enabled to approximate the truth, even if 
 we cannot expect to reach it altogether." 
 
 There are some curious surmises in Galvani's book as 
 to the possible future value of his discoveries in the treat- 
 ment and cure of nervous disease. He recognizes the 
 jdifficulty of their application to pathology, on his own hy- 
 
 'pothesis of an animal electricity as the cause of muscular 
 contraction. But they are interesting in connection with 
 
IN THE STUDY OF THE NERVOUS SYSTEM. II 
 
 the imperfect state of pathological knowledge in his day 
 as compared with the present, and some of his remarks 
 sound almost prophetic. "In regard," he says, "to the 
 cure of paralysis, I see that it is a matter of great uncer- 
 tainty ; for it is not easy to say whether the disease be 
 caused by a degeneration of structure in the nerves and 
 brain, or whether it be due to an obstruction of the sup- 
 posed electrical circuits by the deposit of some non-con- 
 ducting material. But perhaps," he adds, "the whole 
 thing will some day or other be cleared up by further 
 practice and experience." 
 
 Galvani did not have to wait long to see a very impor- 
 tant advance made in the path which he had opened. One 
 of his contemporaries was Volta, who had already beea 
 for fifteen years professor of physics in the University of 
 Pavia, and who was admirably fitted, both by his capacity 
 and his attainments, for treating a new subject with suc-j 
 cess. Volta was greatly attracted by the novelty and 
 character of Galvani's experiments. He repeated them, | 
 with many extensions and variations ; and he not only 
 verified their results, but was enabled to throw a new \ 
 light on the immediate cause of their phenomena. His 
 first "investigations were communicated in the form of two 
 letters to the Royal Society of London in 1793, under the 
 title " An Account of some Discoveries made by M. Gal- 
 vani, with Experiments and Observations on Them." ' In 
 this communication he refers to Galvani's treatise, pub- 
 lished two years before, as containing " one of the most 
 splendid and striking discoveries, as well as the germ of 
 others in addition." 
 
 Volta naturally approached the subject rather from its 
 
 ' Philosophical Transactions of the Royal Society of London for the Year 1793, 
 p. 10. 
 
12 GALVANI AND GALVANIjSM ... 
 
 physical than its phjraiological side, artd. he had a certain 
 mathematical habit of mind that led him .to appreciate the 
 value of quantities in such an investigation. He began 
 by determining, in an approximate way, the amount of 
 ■felectrical stimulus capable of producing: convulsions in 
 'the muscles of the frog. By using successively smaller 
 . and smaller charges from a Leyden jar, he found that, the 
 fl entire and living frog might be convulsed by electric .dis- 
 charges which would give but very faiiit sparks, and 
 which would affect only the most delicate of the elec? 
 trometers then in use. But a recently, killed frog,, pre- 
 pared after the method of Galvani, was more sensitive 
 still. In this condition it could . be made to contract by 
 I an electric discharge fifty or sixty times, more feeble, and 
 quite imperceptible with any electrometer, unless by aid 
 of the condenser. In this way he exhibited Galvani's 
 frog as a new kind of electrometer, or electroscope, of ex- 
 traordinary sensibility ; and he named it, accordingly, the 
 ^"animal electrometer." This showed conclusively that 
 in all the experiments with induced electricity the dis- 
 sected frog might be convulsed by an electric discharge 
 too feeble to be detected by other means. 
 ' Volta then began to investigate the source of electricity 
 in Galvani's third set of experiments ; namely, those with 
 the dissected frog and the metallic arc. Galvani, it will 
 be remembered, attributed this electricity to the different 
 condition of the animal tissues, and- always made his con- 
 nection between the nerve on the one hand and the mus- 
 cle on the other, as he would between the twp surfaces of 
 a Leyden jar. With the connection made in this way the 
 effect is really more striking, because thewbole of ithe gal- 
 vanic current passes through the isolated nerve, and thus 
 j produces a corresponding excitement. But Volta found t 
 
IJ\r THE STUDY OF THE NERVOUS SYSTEM. 13 
 
 that the two separate elements of nerve and muscle re- /" 
 spectively were not essential to the result. If one metal- 
 lic armature were placed on the muscle, and another also 
 on the muscle near by, or if they were placed on corre- 
 sponding muscular parts of the two legs, a contraction 
 ensued on connecting them by the metallic arc. The 
 same thing happened with the nerve. If an armature of 
 silver were placed on one part of the crural nerve above 
 its junction with the muscles, and one of tin-foil at another 
 part of the same nerve still higher up, and connection 
 made between them, the leg was convulsed^ notwithstand- 
 ing that the whole of the muscles, as well as a portion of 
 the nerve, were outside the electric circuit. This did not \ 
 correspond with the idea of an animal electric apparatusj 
 consisting of the nerve and muscle combined. It was 
 necessary to look elsewhere for the source of the elec- 
 tricity under these conditions ; and Volta found it in the 
 contact of dissimilar metals. This contact developed but 
 a minute quantity of electricity, too small tO' be recognized 
 by any other means at the command of the experimenter; 
 but the dissected frog was an" electroscope of such sensi- 
 bility, that it responded to the test, and betrayed the elec- 
 tric discharge by a convulsion. 
 
 Volta was in very much the same position for this part 
 of the discovery as Galvani had been in regard to his own 
 earlier observations. He was compelled to recognize its 
 reality and importance without being able to give its ex- 
 planation. " I confess," he says, " it is not easy to under- 
 stand how or why the application of .dissimilar armatures 
 — that is, of different metals — to two similar parts of the 
 animal, or even to neighboring parts of the same muscle, 
 should disturb the equilibrium of the electric fluid, and 
 drive it from its condition of repose into one of active 
 
14 GALVANI AND GALVANISM 
 
 and continued displacement. But whatever may be the 
 cause of the phenomenon, and whether intelligible or not, 
 it is nevertheless a fact abundantly established by the 
 experiments already detailed, and further corroborated by 
 those which follow." 
 
 For several years Volta continued the study of this 
 subject, and at last found a way of greatly increasing the 
 intensity of the phenomena. This was by multiplying 
 the number of pairs of his dissimilar metals so as to form, 
 the Voltaic pile. His results were given in 1800 in a 
 letter to the Royal Society,' containing a description of 
 his new contrivance. Each member of the pile consisted 
 of a plate of zinc in contact with a plate of silver. This 
 was covered by a layer of moistened paper or membrane. 
 Then followed a second pair of zinc and silver plates, and 
 so on, alternately; the two metals always recurring in the 
 same order, and each pair being separated from those 
 above and below by moist membranes. With this ar- 
 rangement the intensity of the action, on connecting the 
 extremities of the pile, was sufificient to cause shocks and 
 muscular contractions in the hands and arms^ and to affect 
 the senses of sight, hearing, taste, and touch. Its opera- 
 tion was compared to that of the torpedo and electrical 
 eel, and it received the name of the " artificial electrical 
 organ." 
 
 The peculiarity of this discovery was, that it introduced 
 into electrical science two new features. Before that time, 
 electricity had been obtained only by the combined use of 
 different substances, one of which must be a conductor, 
 the other a non-conductor, as in the frictional machine, 
 the Leyden jar, and the electrophorus ; and, when an 
 
 ' Philosophical Transactions of the Royal Society of London for the Year 1800, 
 p. 403. 
 
IN THE STUDY OF THE NERVOUS SYSTEM. 15 
 
 electrified body was touched by a conductor, the whole of 
 its charge was expended, and it could be electrified again 
 only by receiving a new charge from an extraneous source. 
 But in the electric pile Volta found, to his surprise, a 
 source of electricity in substances all of which were con- 
 ductors, and, furthermore, a source which seemed inex- 
 haustible ; because, however often the two ends of the pile 
 were touched, the same shock was repeated with the same 
 intensity. The inherent force of the pile seemed to urge 
 the electric fluid incessantly forward, returning upon itself 
 in a continuous flow so long as the circuit of conductors 
 remained complete. 
 
 Volta attributed this action entirely to the contact of 
 dissimilar metals. This view is plainly expressed in the 
 title of his letter to the Royal Society, and is repeatedly 
 insisted on in the course of the communication. The 
 fluids or moistened membranes interposed between the 
 metallic pairs he regarded only as conductors ; and, when 
 a saline solution was found to be more efficient than water 
 alone, he thought it was because the salt increased the 
 conducting power of the water. In reality, the source of 
 power in the Voltaic pile is the chemical action between 
 the fluid and the metals, one of which is more oxidizable 
 than the other ; and, for every unit of electric force sent 
 through the circuit, a definite quantity of material under-, 
 goes chemical transformation. The contact of dissimilar' 
 metals is not essential to the result; for a current may 
 be produced without it, if we use two different liquids, of 
 which one is more decomposable than the other." 
 
 Neither the first nor the second explanation of the 
 phenomena observed was therefore entirely right, as we 
 
 ' Daniell: Introduction to the Study of Chemical Philosophy. London, 1843, 
 p. 492- 
 
l6 GALVANI AND GALVANISM 
 
 understand it. Volta imagined the metals in his pile to 
 act by contact alone, while they are really consumed by 
 oxidation. In Galvani's experiment, the connecting arc 
 where the two metals join is, as Galvani supposed, a con- 
 ductor, and nothing more; but its different extremities, 
 when applied to the animal tissues, form with them a gal- 
 vanic battery of a single cell, and thus produce the current 
 \vhich excites their contraction. We now use it for physi- 
 ological purposes in a different way. We place the two 
 metallic plates in a cup of acidulated fluid, and make the 
 returning current pass through the muscles and nerve. 
 But the effect is the same, for the active force of the cur- 
 rent is equal in both directions. 
 
 The results obtained by these two investigators were 
 distinct from each other, but of almost equal importance. 
 Galvani discovered the electric action on nerves and mus- 
 cles which bears his name. Volta gave to science a new 
 I apparatus, by which current electricity is transmitted in 
 V a continuous circuit. Each investigator was partially at 
 fault in the theoretical explanation of his own discovery. 
 But the value of the discovery has remained, and has even 
 largely increased in the course of a century, notwithstand- 
 ing the difference in its interpretation. It also appears, 
 from the history of the circumstances, that the second of 
 these discoveries was a consequence of the first ; and 
 nothing can show more clearly the unbroken connection 
 of events in the progress of science, which may some- 
 times extend to the most unexpected ramifications. It is 
 plain that we should not be to-day in possession of the 
 electric light, were it not for Volta's discovery of current 
 electricity ; and Volta produced his electric pile in trying 
 to investigate the contraction of Galvani's frogs. 
 
 During the early part of the present century, experi- 
 
IN THE STUDY OF THE NERVOUS SYSTEM. 1/ 
 
 menters were busily occupied with galvanic electricity. 
 They studied its action in a great variety of ways, and 
 thus became acquainted with its mode of operation, and 
 able to appreciate its phenomena. They found that when 
 it was transmitted through any portion of a muscular n 
 nerve it produced contraction at the instant of closing the 
 circuit ; that afterward, while flowing through the nerve 
 in a uniform current, it was without effect ; and that / 
 contraction again occurred when the current was discon- 
 tinued. Even during the passage of the current, any i 
 sudden variation in its intensity, either of increase or \ 
 diminution, would produce the same effect. It was the 
 change in the electrical state of the parts, rather than 
 their actual condition, which operated as a stimulus and 
 provoked the contractions. The direction of the current, 
 the length of nerve included within the circuit, and the 
 frequency of making and breaking the connection, — all 
 had a certain influence in the result. Experimenters found 
 themselves provided with a new agent, by which they 
 could investigate nervous action at their leisure, in ani- 
 mals deprived of life, with the nerves and muscles ex- 
 posed to view, and with far more delicacy and certainty 
 than ever before ; and the familiarity thus acquired with 
 the operation of the galvanic stimulus prepared them for 
 its more effective use in future investigations. 
 
 The next event of sufficient consequence to form an 
 epoch in the history of nervous physiology was the dis- 
 covery, in 1822, of the distinction of motor and sensitive 
 properties' in the two roots of the spinal nerves. Eleven 1 
 years before, Sir Charles Bell ' had made some experi- 
 ments on the spinal nerve roots of a recently killed rabbit, ' 
 
 ' Idea of a New Anatomy of the Brain ; submitted for the Observation of his 
 Friends. By Charles Bell, F.R.S.E. 
 
I8 CALVANI AND GALVANISM 
 
 in which it appeared that mechanical irritation of the 
 anterior roots caused convulsion in the corresponding 
 muscles, while a similar irritation of the posterior roots 
 had no such effect. This, however, was not supposed to 
 show an anatomical separation between the two powers of 
 motion and sensibility, but between those of volition and 
 consciousness on the one hand, and involuntary nervous 
 action on the other. The ideas of the author on this sub- 
 ject were not accepted by his colleagues. In fact, they 
 were not really published, but only printed in pamphlet 
 form for private distribution. They hardly attracted the 
 notice of the profession, and had no influence on the 
 medical doctrines of the day. 
 
 Subsequently, in 1821, Bell published' the remarkable 
 observation that if the seventh cranial nerve, distributed 
 ! to the face, were divided in a living animal, the move- 
 \ ments of facial • expression were abolished ; while the 
 ; faculty of sensation could be destroyed by cutting the 
 corresponding branches of the fifth pair.. Thus the two 
 main properties of nervous endowment, generally asso- 
 ciated with each other, occupied in this instance distinct 
 situations ; since the seventh was shown to be a nerve of 
 motion only, the sensibility of the face being supplied 
 from another source. This fact was connected, in the re- 
 searches of Sir Charles Bell, with theoretical considera- 
 tions of a different bearing ; but it had evidently a great 
 importance of its own, and was received on all sides with 
 much interest. It especially attracted the attention of 
 Magendie, then at the height of his activity in physio- 
 logical investigation. Magendie repeated Bell's experi- 
 ments on the seventh cranial nerve, and verified their 
 results as to its exclusively motor properties. But he was 
 
 ' Philosophical Transactions of the Royal Society. London, 1821, p. 398. 
 
IN THE STUDY OF THE NERVOUS SYSTEM. 19 
 
 also intent on exploring various other parts of the nervous 
 system ; and in 1822 he performed and published his ex- 
 periments on the spinal nerve roots.' His description is 
 a model of directness and simplicity, free from any un- 
 warranted inference or assumption. " I had long been 
 wishing," he says, "to try the experiment of dividing the 
 posterior roots of the spinal nerves, but had never suc- 
 ceeded in doing so, owing to the difficulty of opening the 
 vertebral canal without wounding the spinal cord, and 
 inflicting severe or fatal injury upon the animal. But a 
 month ago I received at the laboratory a litter of pups 
 only six weeks old ; and it seemed a good opportunity for 
 another attempt at the operation. This time, in fact, I 
 succeeded, by the aid of a very sharp scalpel, in laying 
 bare, almost at a single stroke, the posterior half of the 
 spinal cord with its membranes. I then had no difficulty, 
 after opening the dura mater, in bringing into view the 
 posterior roots of the lumbar and sacral nerves ; and, by 
 lifting these roots on the blades of a pair of fine scissors, 
 I was able to divide them on one side without injury to 
 the spinal cord. Not knowing what would be the effect 
 of this operation, I closed the wound by a suture in the 
 integument, and kept watch of the animal. At first it 
 looked as if the limb on that side were entirely paralyzed. 
 It was insensible to punctures and to pressure, and also 
 appeared motionless ; but soon afterward I was surprised 
 by seeing it move very distinctly, although it was com- 
 pletely and permanently insensible. After trying a sec- 
 ond and a third experiment with exactly the same result, I 
 began to think it probable that the posterior roots of the 
 spinal nerves might have a function distinct from that of 
 
 • Journal de Physiologie ExpSrimentale et Pathologique (Paris, 1822), tome ii. 
 p. 276. 
 
20 GALVANI AND GALVANISM 
 
 the anterior roots, and more especially devoted to sensi- 
 bility. 
 
 " I next thought of dividing the anterior roots, leaving 
 the posterior roots entire ; but that was a thing more easily 
 said than done. There appeared to be no way of getting 
 at the anterior surface of the cord without involving the 
 posterior roots ; and at first it seemed a hopeless under- 
 taking. After considering the matter for a day or two, I 
 tried to reach the anterior roots with a sort of narrow- 
 bladed cataract-knife, by passing it in front of the posterior 
 roots, and then turning its cutting edge forward against 
 the bodies of the vertebrae. This plan failed, owing to 
 the impossibility of avoiding hemorrhage from the large 
 veins in the vertebral canal ; but, while making the at- 
 tempt, I found, that, by drawing aside the dura mater, I 
 could catch a glimpse of the anterior roots just where they 
 are about to pass through the investing sheath. This was 
 enough ; and in a few seconds I had divided -as many of 
 them as I wished, on one side only. It may be imagined 
 with what curiosity I awaited the result. It finally came 
 in a perfectly unequivocal form ; for the limb, though re- 
 taining its sensibility, was completely relaxed and motion- 
 less. Finally, not to leave any thing undone, I divided 
 both the anterior and posterior roots, causing entire loss 
 of sensibility and motion." 
 
 Magendie began his experiments, therefore, by dividing 
 the nerve-roots, and thus abolishing their functions. In 
 pursuing the subject, he tried the effect of their irritation, 
 employing for this purpose both mechanical agents and 
 the stimulus of galvanism. The result of these experi- 
 ments corresponded in general with those obtained by the 
 method of division ; that is, galvanization of the anterior 
 roots caused muscular contraction, and that of the poste- 
 
IN THE STUDY OF THE NERVOUS SYSTEM. 21 
 
 rior roots sensation. There were also certain other phe- 
 nomena which did not altogether coincide with the doctrine 
 of a complete separation between the two functions, and 
 which were not fully understood until some years later. 
 But Magendie took cognizance of every experimental fact, 
 whether he understood it or not ; and his own subsequent 
 researches on " recurrent sensibility " explained many of 
 the irregularities which he at first encountered. 
 
 This distinction between the spinal nerve roots was of 
 greater importance, because it indicated a general plan 
 of arrangement for the nervous system throughout the 
 body. It immediately became a matter of criticism and- 
 verification for the leading physiologists of Europe ; and 
 the result was a complete acceptance of Magendie's dis- 
 covery. In Germany, Johann Miiller, then professor of 
 anatomy and physiology in the University of Bonn, 
 endeavored to avoid the difficulties of so serious an 
 operation on warm-blooded animals by experimenting on 
 frogs. He examined the spinal nerve roots in these 
 animals, both by the method of section, by'mechanicar 
 irritation, and by galvanism.' 
 
 "These experiments," he says, "have been rewarded 
 with the most brilliant success. They are so easy of 
 application, so sure and so decisive, that any investigator 
 may now readily satisfy himself of one of the most im- 
 portant truths in physiology. The phenomena are so 
 regular and satisfactory, that, for simplicity and certainty 
 of results, they fully compare with any crucial experiment 
 in the physical sciences. Galvanization of the separated 
 anterior roots at once causes active convulsions ; that of 
 the posterior roots never gives rise to any sign of spas- 
 modic action." 
 
 • Handbuch der Physiologie des Menschen. Coblentz, 1837. Band i. p. 651. 
 
22 GALVANI AND GALVANISM 
 
 In this way the distinct endowment of the two kinds 
 of nerve-fibres was experimentally established. Once 
 placed on this footing, the pursuit of nervous physiology 
 was greatly increased in efficiency and extent. By apply- 
 ing the galvanic stimulus to a spiAal nerve above or below 
 the point of section, its mode of action was determined 
 by the excitability of its motor or sensitive fibres. The 
 same method was employed for the cranial nerves, both 
 externally and at their roots ; and every branch of inoscu- 
 lation was scrutinized by the same means. It is hardly 
 possible to overestimate the change thus iijtroduced, into 
 the study of the nervous system, and the facilities which 
 it supplied for further investigation. 
 
 We now come to Marshall Hall s discovery of the reflex 
 action of the spinal cord. Up to this time, the motor and 
 sensitive properties of the nervous system had been under- 
 stood by physiologists as almost wholly subservient to 
 voluntary motion and conscious sensibility. These func- 
 tions resided in the brain, as the organ of intelligence and 
 the source of all spohtaneous action. From it. the motor 
 nerves transmitted to the muscles the commands of. the 
 will, while the sensitive nerves brought to it from without 
 the impressions made on the integument. The spinal 
 cord was part of this apparatus of transmission. Like 
 the spinal nerve roots, under the influence of galvanism, 
 its posterior columns were found to be sensitive, and its 
 anterior columns excitable; and its complete division at 
 any one point'aboUshed voluntary movement and sensation 
 in the parts below. It was the channel through which 
 the spinal nerves held their connection with the brain. 
 
 But Hall observed, that, notwithstanding the loss of 
 sensation and volition after removal of the brain, the 
 animal might still be capable of motion in the limbs, 
 
IN THE STUDY OF THE NERVOUS SYSTEM. 2$ 
 
 provided the spinal cord remained. Although phenomena 
 of this kind had already been noticed in several instances, 
 they had not been demonstrated with sufficient distinct- 
 ness to fix the attention of physiologists. Hall's observa- 
 tions were first announced in a communication to the 
 London Zoological Society in 1832. They were further 
 embodied in his "Lectures on_.the Nervous System and 
 its Diseases," in 1836, and still more formally presented 
 in his "Memoirs on the Nervous System," in 1837. 
 Their simplest demonstration was given by him in the 
 following way : In a living and uninjured frog the signs 
 of sensation and volition are manifested whenever the 
 skin is irritated at any point, since the animal feels the 
 impression, and responds to it by a voluntary motion. 
 When the head is cut off, or the spinal cord divided at 
 its upper part, the limbs are paralyzed, and sensation is 
 • abolished. But if, while the animal is in this condition, 
 one of the feet be pinched, the limb is drawn upward ; 
 and the movement may be repeated as often as the irrita- 
 tion is applied. Such a movement is very different from 
 that- caused by galvanizing a motor nerve ; since the stimu- 
 lus in this instance is applied to the skin, and the muscles 
 react in consequence. Both skin and muscles must retain 
 their connection with the spinal cord ; since, if this con- 
 nection be cut off, no movement takes place on pinching 
 the foot. Finally, the nerves remaining uninjured, if the 
 spinal cord be broken up, all reaction ceases, and irritation 
 of the skin has no further effect. But does not such a 
 violence destroy the physiological property of the muscles, 
 and in that way prevent their contraction .' This doubt is 
 removed by applying a galvanic current to the muscles 
 themselves, when they are at once convulsed, showing 
 that their contractile power is unimpaired.! 
 
 ' Lectures on the Nervous System and its Diseases. London, 1836, p. 19. 
 
24 GALVANI AND GALVANISM 
 
 Thus, it is the spinal cord which acts, independently of 
 the brain, as a medium of communication between the 
 integument and the muscles. The stimulus conveyed 
 inward, through the sensitive nerves to the cord, is thence 
 reflected outward through the motor nerves to the muscles. 
 From this circumstance it received its name of " reflex 
 action ; " and, since it was first studied and demonstrated 
 in the spinal cord, it was generally known as the " reflex 
 action of the spinal cord." 
 
 But the same form of activity was afterward found to 
 be very widely extended in the nervous system. The 
 medulla oblongata has its own centres of reflex action, 
 either directly or indirectly essential to the continuance 
 of life. Wherever there is a ganglionic mass of nervous 
 matter, with motor and sensitive fibres originating from 
 it, there is a similar focus of nervous power, often quite 
 disconnected with consciousness and volition. In a state 
 of absolute insensibility, in man or animals, a touch upon 
 the cornea will cause closure of the eyelids, irritation of 
 the anus will increase the contraction of the sphincter, 
 and the contact of a solid body with the fauces will excite 
 the movement of deglutition ; and in all these instances 
 the reaction disappears when its special nervous centre is 
 destroyed. Similar facts were soon observed in man in 
 cases of paralysis, as where movements are produced in 
 paraplegic limbs without the knowledge of the patient; 
 and nearly all the phenomena of convulsive affections 
 were seen to have their origin in some unusual irritation 
 of a nervous centre, or in the morbid exaggeration of its 
 excitability. From that time forward the reflex action of 
 the nervous system entered more or less into the whole 
 study of its normal and diseased conditions. 
 
 The next topic of special interest in this connection is 
 
IN THE STUDY OF THE NERVOUS SYSTEM. 2$ 
 
 the influence of the nervous system on the organs of circu- 
 lation. The earlier approach to definite knowledge on this 
 subject was a very slow one. It consisted mainly in estab- 
 lishing the fact of contractility in the arteries, and was 
 accomplished by experimental inquiries extending over a 
 long time, — from those of Hunter, on the arteries of 
 animals, in 1793, to those of Kolliker,' in 1849, on the con- 1 
 striction caused by galvanism in the popliteal and tibial , 
 arteries of an amputated human limb. A new epoch in 
 the physiology of the circulation was reached in 185 1, 
 when Claude Bernard ^ published the discovery that divis- 
 ion of the sympathetic nerve in the neck is followed by 
 enlargement of the blood-vessels on the corresponding side , 
 of the head. This effect is so striking and so constant, 
 that, when once announced, there was no difficulty in its 
 verification, and no doubt as to its reality. Almost imme- 
 diately after the section of the nerve, an increased vas- 
 cularity becomes visible in the conjunctiva, the mucous 
 membrane of the nostril, lip, tongue, and cheek, and in all 
 parts of the skin on the affected side. It is most distinctly 
 seen in the ear of the white rabbit, because the organ 
 presents a thin expansion of semi-transparent tissue, con- 
 venient for observation, and because the two ears, placed 
 side by side, afford a ready criterion of any change in vas- 
 cularity. In the first report of these experiments, the 
 attention of the observer was principally directed to the 
 local increase of temperature, which also follows division 
 of the sympathetic ; but this was afterward seen to depend 
 on the greater activity of the circulation, which was then 
 recognized as the primary and characteristic result of the 
 operation. 
 
 • Zdtschrift fur wissenschaftliche Zoologie. Leipzig, 1849. Band 1. p. 259. 
 
 ' Comptes rendus de la Soci^t^ de Biologie. Paris, ann^e 1851. Tome iii. p. 163. 
 
Z6 GALVANI AND GALVANISM 
 
 This fact, of enlargement of the blood-vessels from divis- 
 ion of the sympathetic nerve, at once excited a lively, 
 interest among physiologists. Hardly a year had elapsed,- 
 when a second observation, equally important with the first, 
 was made almost simultaneously by Brown-S^quard in 
 Philadelphia,' Bernard in Paris,* and Waller in London ; 3 
 namely, that the condition of the circulation on that side 
 of the head where the sympathetic has been dividgd may 
 be regulated at will by experimental means. Suppose that 
 increased vascularity has been produced by division of the 
 sympathetic in the neck : if the stimulus of galvanism be 
 now applied to the divided nerve above its point of section, 
 all the previous results of the operation disappear. The 
 blood-vessels contract, the volume of the circulation dimin- 
 ishes, the local temperature is reduced, and the parts 
 resume their normal color, or even become more pallid than 
 beforCj When the galvanization is suspended, the former 
 conditions return, with all the accompanying phenomena of 
 vascularity, temperature, and redness ; and the circulation 
 in the part may be in this way alternately increased and 
 diminished for many successive repetitions of the experi- 
 ment. 
 
 It thus appears that the muscular coat of the arteries, 
 supplied with nerve-fibres from the sympathetic, is influ- 
 enced by them in nearly the same way as the voluntary 
 muscles are controlled by the cerebro-spinal nerves. Divis- 
 ion of the sympathetic paralyzes the involuntary muscular 
 fibres, relaxes the arterial walls, and allows a larger quan- 
 tity of blood to pass through the vessels of the part. Gal- 
 vanization of the nerve, on the other hand, stimulates the 
 muscular fibres to contraction, narrows the caliber of the 
 
 ' Philadelphia Medical Examiner. 1852. Vol. viii. p. 489. 
 
 ^ Comptes rendus de la Soci^te de Biologie. Paris, 1852. Tome iv p. 168. 
 
 3 Comptes rendus de I'Acad^mie des Sciences. Paris, 1853. Tome xxxvi. p. 378. 
 
//V THE STUDY OF THE NERVOUS SYSTEM. 2/ 
 
 vessels, and so reduces the volume of the circulating blood. 
 The knowledge of these facts introduced into the nomen- 
 clature of the nervous system a new title. There were 
 evidently nerve-fibres which acted upon the blood-vessels 
 to call into operation their contractile power; and the 
 nerves possessing such a function, then known for the first 
 time, naturally , received the name of the " vaso-motor 
 nerves." 
 
 But, in following out this subject, an observation was 
 soon met with of very unexpected character ; namely, that 
 certain other nerves, on being stimulated, instead of pro- 
 ducing contraction of the blood-vessels, caused their relaxa- 
 tion, and thus increased the activity of the circulation.' 
 This was first shown by Bernard in the case of the sub- 
 maxillary gland. This organ is supplied with sympathetic 
 fibres from the superior cervical ganglion and the carotid 
 plexus, and with cerebro-spinal fibres from the lingual nerve 
 and the chorda tympani. Galvanization of its sympathetic 
 filaments produces, as in other similar instances, contrac- 
 tion of the vessels, and a diminished blood-supply. But if 
 the stimulus be applied to the lingual nerve above the 
 situation of the gland, or to the chorda tympani, which 
 unites with it, the result is exactly the contrary : the 
 blood-vessels enlarge and the circulation is more active so 
 long as the galvanization continues ; and this effect is 
 equally marked if the nerve be divided, and galvanized 
 between its point of section and the gland. 
 
 A similar influence was found to reside in other parts of 
 the nervous system ; and the nerves possessing the power 
 of thus causing vascular enlargement were called " dilator 
 nerves." No sooner was this fact established in a general 
 way, than it served to explain a singular phenomenon which 
 had been noticed many years before, but which had thus 
 
28 GALVANI AND GALVANISM 
 
 far been regarded as exceptional ; namely, the influence of 
 the pneumogastric nerve on the action of the heart. As 
 a general rule, if the nerve going to a muscular organ 
 be divided, the muscle is paralyzed ; and, if the nerve be 
 stimulated, there is muscular contraction. As the heart re- 
 ceives filaments from the pneumogastric nerve, we should 
 I naturally expect that its action would be diminished by 
 ) section of this nerve, and increased by its stimulation. 
 I But the effect is really the reverse. If the poles of a gal- 
 vanic apparatus be applied to the pneumogastric nerve in 
 the neck, the cardiac pulsations are reduced in frequency ; 
 'and, when the strength of the current is increased to a 
 certain degree, they stop altogether. The heart lies quies- 
 cent, in a state of relaxation, its movements remaining in 
 abeyance while the galvanization goes on ; and, when it is 
 suspended, they recommence with undiminished energy. 
 The influence exerted in this case is not reflex, but direct, 
 in its operation : for if the nerve be divided, and galvanized 
 above its point of section, there is no result ; but, if the 
 stimulus be applied below the section, its retarding action 
 on the heart is at once manifest. Furthermore, the power 
 of this nerve to restrain the cardiac movements, like the 
 i motor influence of a spinal nerve, is limited in duration. 
 You cannot permanently arrest the heart, and so kill the 
 animal, by continued galvanization of the pneumogastric. 
 When the galvanization of the nerve has been kept up for 
 \ a certain time, the heart begins to beat again. Its pulsa- 
 \ tions recur at first slowly, afterward more frequently ; and 
 at last they are restored in full regularity, notwithstanding 
 ithe continuance of the galvanic current. The nerve has 
 I lost its power by exhaustion, and cannot again manifest 
 its controlling force, unless allowed to recover by repose. 
 But the heart is still sensitive to the same influence ; and, if 
 
IN THE STUDY OF THE NERVOUS SYSTEM. 29 
 
 the electrodes be shifted to the pneumogastric of the oppo- 
 site side, it stops as quickly as before. 
 
 It. must be admitted, therefore, that the influence of 
 the pneumogastric, whatever it may be, which controls the 
 heart's movement, is transmitted from within outward to 
 the peripheral extremities of the nerve ; and that it acts in 
 a positive manner, though producing a negative result. It 
 is the most striking illustration of a kind of action in the 
 nervous system unlike any of those formerly known,' but 
 not the less real for being difficult to understand. This is 
 the so-called " action of arrest," an influence which passes 
 through a nerve from its origin to a muscle, and by which 
 the muscular contraction is suspended. As often happens 
 in such cases, when the existence of this mode of action 
 was once realized, it appeared that there were other in- 
 stances of the same thing which had been overlooked. 
 All the sphincter muscles, though habitually in a state of 
 involuntary contraction, are suddenly relaxed at certain 
 periods by an influence coming from within. The blood- 
 vessels generally receive both kinds of nervous impression ; 
 and, by the varying preponderance of one or the other, they 
 are alternately made to contract or dilate, with all the 
 accompanying changes of local circulation. In this way 
 it became possible to explain the mechanism of temporary 
 physiological congestions, as in secreting glands, or in the 
 alimentary canal during digestion; and those of longer 
 continuance, with increased nutrition, like the growth of 
 the uterus and mammary glands during pregnancy,, as well 
 as morbid disturbances of the circulation in disease. 
 
 Quite a different line of investigation was inaugurated 
 by Helmholtz, in 1851, for determining the rapidity with 
 which nervous action is transmitted through the motor 
 nerves.' The idea of measuring, with any approach to 
 
 ' Comptes rendus de I'Academie des Sciences. Paris, 1851. Tome xxxiii. p. 262. 
 
30 GALVANI AND GALVANISM 
 
 numerical precision, the movement of the intangible nerve- 
 force through its fibres, would seem at first almost beyond 
 the scope of reality ; and yet it was accomplished with sat- 
 isfactory success, and by perfectly genuine experimental 
 methods. It would have been impossible, were it not for 
 improvements in the galvanic apparatus and the register- 
 ing machines, which have played so important a part in 
 the more recent investigation of animal physics. The 
 knowledge and use of induced electric currents we owe to 
 Faraday; and their discovery in 183 1, with all the related 
 phenomena of electro-magnetism, magneto-electricity, and 
 the production of instantaneous and rapidly alternating 
 opposite currents, practically revolutionized the use of 
 electricity for medical purposes. It also supplied especial 
 
 ' facilities for experiments on the rate of transmission of the 
 nerve-force. 
 
 The conditions necessary for such an experiment were 
 twofold : first, an instantaneous induced current, for caus- 
 ing a single muscular spasm ; and, secondly, an automatic 
 registering apparatus, which should mark the exact time, 
 both of the electric stimulus and of the muscular action. 
 By this means a definite result was obtained. With the 
 
 / electrodes applied to the muscles of a frog's leg, an in- 
 terval amounting to the one-hundredth part of a sec- 
 
 1 ond appeared between the closure of the circuit and the 
 contraction of the muscle. The muscular contraction, 
 therefore, was not an instantaneous effect, but required a 
 certain time to get under way after the application of 
 the stimulus. This interval was not perceptibly altered on 
 
 J applying the electrodes to the nerve at or near its entrance 
 
 \ into the muscle ; but, if they were applied higher up on 
 the nervous trunk, the delay became longer; and it was 
 increased, in subsequent trials, exactly in proportion to the 
 
IN THE STUDY OF THE NERVOUS SYSTEM. 31 
 
 distance between the muscle and the point of nerve-stimu- 
 lation. It represented, accordingly, the time required for , 
 the nerve-force to traverse a given length of " nerve-fibre ; 
 and, by repeating the test under various conditions, its rate I 
 of movement was fairly determined. 
 
 These experiments, first performed on the nerves and 
 muscles of the separated frog's leg, were afterward ex- 
 tended to those of the living man, the electric stimulus 
 being applied to the skin over the situation of a nerve at 
 different points, and the contraction indicated by the swell- 
 ing of the parts over the muscle. In all the investigations 
 thus far, the nerve was excited by the artificial stimulus of 
 electricity. Subsequently, Burckhardt ■ simplified the ex- 
 periment, and increased the value of its results, by employ- 
 ing, instead of electricity, the natural stimulus of volition. 
 The subject being placed in connection with a proper 
 registering apparatus, the signal for voluntary effort was 
 given by the sound of a bell, and the movement was per- 
 formed in different instances by different muscles. Under 
 these conditions, the time necessary, both for volition and 
 for the mechanism of muscular contraction, would be the 
 same in all cases; but that required for traversing the 
 motor nerve would vary according to the muscle employed. 
 A voluntary impulse starting from the brain would arrive 
 at the deltoid muscle after travelling a certain distance ; 
 but it would follow a longer route to reach the adductor of 
 the thumb. The distribution of the crural nerve to the 
 quadriceps extensor muscle is comparatively remote from 
 its origin, and that of the sciatic nerve to the dorsal mus- 
 cles of the foot more distant still. The difference in the 
 time of muscular contraction observed in these cases cor- 
 responded with the different lengths of nerve conveying 
 
 ' Die physiologische Diagnostik der Nervenkrankheiten. Leipzig, 1875, p. 32. 
 
32 GALVANI .AND GALVANISM T 
 
 the Stimulus; and it gave for the passage of the voluntary, 
 impulse in man through the motor nerves an average rate 
 of twenty-seven metres per second. ' 
 
 A similar contrivance for measuring the transmission of 
 tactile impressions through the sensitive nerves gave their 
 rate of movement as forty-seven metres per second, show- 
 ing a greater rapidity of transmission for sensitive impres- 
 sions than for motor impulses ; and, by comparing the 
 result of further experiments with the known quantities 
 obtained in this way, a close estimate was reached of the 
 time needed for the operation of the different senses, and 
 even for the cerebral acts of perception and will. 
 
 When these observations were made on different persons, 
 there was always a certain amount of variation in the re- 
 
 ' suit ; the nervous action being in some cases more rapid, 
 
 ■ in others coinparatively slow. This brought within the 
 range of definite physiological experiment a fact first 
 noticed in astronomical observatories ; namely, that two 
 observers, both watching for the same event, seldom see 
 
 \and record it at the same time. There is a difference in 
 the quickness with which they receive its impression on 
 
 : the senses, and in ea:ch case there is a certain amount of 
 delay; so that, in neither the one nor the other, is the phe- 
 nomenon perceived at the time of its actual occurrence. 
 In astronomical operations where extreme accuracy is re- 
 quired, as in transit observations for the determination of 
 longitude, this personal imperfection of the observer needs 
 to be corrected from a previous examination of his habitual 
 error. In the report of the United States Geographical 
 Surveys for 1877, it is stated by Dr. Kampf that the per- 
 sonal error from this source varies somewhat in the same 
 individual from day to day ; so that its amount should be 
 ascertained, and the proper correction made for each per- 
 son, whenever a longitude observation is to be taken. 
 
IN THE STUDY OF THE NERVOUS SYSTEM. 33 
 
 . There is. still another point of interest in connection 
 with the modern study of the nervous system ; namely, 
 the localization of function in different regions of the 
 brain. 
 
 The most striking part of this subject relates to the 
 special centres for motion and sensation in the cerebral 
 convolutions. There are few discoveries which have 
 seemed more at variance with our former convictions than 
 that of the existence of these centres. Both the substance 
 and the surface of the cerebrum had often been subjected 
 to experimental examination, both in the living and the 
 recently killed animal, without showing any signs of mus- 
 cular reaction ; and it was the universal belief among ■■ 
 physiologists, that none of its parts were directly sub- ' 
 servient to any form of motion or sensibility. So indus- 
 trious and skilful an observer as Longet ' declared, in 1869, \ 
 that he had "irritated by mechanical means the white sub-;' 
 stance of the hemispheres in dogs, cats, rabbits, and birds, ,' 
 and had stimulated it by' the application of potassa, nitric 
 acid, or the actual cautery, as well as by the passage of 1 
 electric currents in various directions, without ever bring- 1 
 ihg into play the involuntary muscular contractility or X 
 convulsive movements ; and similar applications to the gray \ 
 substance of the convolutions were equally without effect." 
 These failures made it seem hopeless to anticipate any 
 further result from direct exploration of the cerebral sub- 
 stance. The brain was generally regarded as so exclusively \ 
 the organ of intelligence, that it could not be expected to ) 
 respond to the irritation of physical agencies. In the 
 extremely condensed and valuable work of Ecker on the 
 convolutions of the brain, the author says in his preface, 
 that " the accurate observation of patients by their physi- \ 
 
 ' Traits de Physiologie, 3me Edition, Paris, 1869. Tome iii. p. 146. 
 
34 GALVANI AND GALVANISM 
 
 \ cians,«in connection with careful autopsies, is the only 
 \means by which we can ever hope to learn the physiologi- 
 cal sigliificance of particular cerebral convolutions." 
 
 This preface was dated March, 1869 ; and in 1870 Fritsch 
 and Hitzig ■ discovered, by experiments with galvanism on 
 the dog's brain, that there are certain parts of the cerebral 
 convolutions where this stimulus always produces definite 
 and unmistakable movements on the opposite side of the 
 body. The contraction of certain groups of muscles, and 
 consequently particular movements in the trunk or limbs, 
 J are connected with the stimulation of particular points of 
 |the brain ; and, when such a point is once found, the cor- 
 j/iresponding movement may be reproduced at will by repeat- 
 \ing the application of the stimulus. There is plainly, in 
 some way or other, a communication, through definite 
 nervous routes, from the special centre of motion on the 
 surface of the hemisphere to the motor tract in the medulla 
 ahd spinal cord, and thence to the muscle which performs 
 the contraction. In all the animals used for experiment, 
 these centres are grouped in certain regions, while other 
 portions of the cerebral surface show no similar indications ; 
 and by comparing their position in different species, aided 
 by observations in human pathology, it appears that in man 
 the motor centres for the body and limbs of the opposite 
 side are mainly located in the anterior and posterior cen- 
 tral convolutions, immediately bordering on the fissure of 
 Rolando. 
 
 Thus the earlier failures ana the more recent success in 
 the discovery of the motor centres are both explained. It 
 is true that a large part of the cerebral surface is unexcita- 
 ble by artificial means. You may apply the galvanic 
 
 ' Archiv fiir Anatomb, Physiologie, und wissenschaftliche Medicin. Leipzig, 
 1870, p. 300. 
 
IN THE STUDY OF THE NERVOUS SYSTEM. 35 
 
 electrodes to twenty different points of the convolutions 
 without the least sign of a muscular contraction. But on 
 the twenty-first trial you may strike one of these centres, 
 and then the muscular spasm immediately follows. We 
 are now so well acquainted with their probable location in 
 any particular brain, that we need not lose a great deal of 
 time in finding one of them ; but, before the geography 
 of their distribution was known, it is not surprising that 
 experimenters should have overlooked their existence. 
 
 The account given of their discoveries by Fritsch and 
 Hitzig was exceedingly well expressed, and bore internal 
 evidence of its faithfulness of description. All the details 
 of experimental procedure were fully explained ; and the 
 results were stated in such a way that other observers 
 could easily follow in the same direction, and test their 
 reality. Some doubt has been entertained in various 
 quarters as to the interpretation of the phenomena, and 
 particularly how far the muscular contractions might be 
 due to a diffusion of the galvanic current beyond the limits 
 of its immediate locality. But this doubt was removed 
 after repeating the experiments by a variety of methods ; 
 and the existence of the motor centres was corroborated 
 by subsequent discoveries in the minute anatomy of the 
 parts, and the local alteration of structure in cases of hemi- 
 plegia. The subject is still so new, and in so active a 
 condition of development, that it can hardly be presented 
 in the form of a complete or well defined physiological 
 doctrine. But it is evidently a matter of great importance, 
 and is probably receiving at this time a larger share of 
 attention than any other single topic relating to the ner- 
 vous system. 
 
 Its latest extension is connected with the centres off 
 sensation in the cerebral hemispheres. As some parts of i 
 
36 GALVANI AN-D GALVANISM 
 
 the convoluted surface of the brain are plainly, subservient 
 \ to muscular action, it is natural to infer that the remaining 
 Sunexcitable portions may have a similar connection with 
 (sensibility; and it is asserted by some, with more or less 
 confidence, that the senses of touch, taste, smell, sight, 
 and hearing are separately located in as many different 
 regions of the cerebral cortex. The experimental evidence 
 of these localizations is far from being altogether satis- 
 factory ; but in one instance, at least, it is very striking, 
 and indicates beyond doubt a close relation of visual sensi- 
 , bility with the " angular convolution " on the pqstgrior and 
 'lateral part of the cerebral hemisphere.^ If this convolu- 
 ' tion be extirpated, the operation is followed by blindness 
 of the opposite eye, without any other perceptible disturb- 
 ance of either motion or sensibility. As other parts of 
 the brain-surface, of equal or greater extent, may. be re- 
 moved without causing impairment of vision, it is difficult 
 to avoid the conclusion that this region has a special con- 
 nection with the sense of sight. The exact nature of the 
 connection will doubtless be better understood from further 
 investigation. 
 
 The complete history of physiological science for the last 
 hundred years, in regard to the nervous system, can hardly 
 be given in the space of a single lecture. But its most 
 important advances are so connected with each other, that 
 they have a relation very much like that of cause and 
 effect. When a new subject of inquiry is first opened, the 
 progress is for some time a slow one. There are diffi- 
 culties in the way, which must be overcome by repeated 
 experiments, by gradual improvement in the apparatus, 
 and by better methods of procedure. The causes of the 
 phenomena are imperfectly understood, and their relation 
 with other observed facts is not immediately, apparent 
 
IN THE STUDY OF THE NERVOUS SYSTEM. 37 
 
 But when the knowledge acquired has reached a certain 
 point, its advance becomes more rapid. Every addition 
 enlarges the circle of its operations, and enables it to 
 execute them with greater facility. And the results at-i 
 tained by this means are not always those most directly 
 anticipated. One discovery often leads to another by 
 bringing into view incidental facts, which, in turn, become ' 
 the sources of new information ; and in that way it creates 
 opportunities for future progress which are sometimes real- 
 ized in their fullest extent only after an interval of several 
 generations. 
 
 There is no more interesting department of physiologi- 
 cal study at the present day than that of the vaso-motor 
 nervous system. Since it was first practically inaugurated 
 by Bernard, thirty years ago, it has bepn cultivated by 
 many observers, and has received a wide extension in many 
 directions. It touches on most important points of pathol- 
 ogy, as well as the functions of health. The connection 
 between secretion and blood-supply, the mechanism of 
 congestions, the dependence of external disturbances of the 
 circulation on disease of internal parts, the red cheeks of 
 pneumonia, the hectic of pulmonary phthisis, and the exist- 
 ence of nervous centres in the cerebro-spinal system, where 
 these changes are controlled by reflex action, are all made 
 capable of investigation by knowledge which has been de- 
 rived from this source. But how could their study have 
 been even attempted, unless we were already in possession 
 of the simpler facts of reflex action of the spinal cord, 
 and the different behavior of motor and sensitive nerve- 
 fibres ? All the variations in the effect produced by elec- 
 tric stimulus of different kinds and intensity, the compara- 
 tive influence of direct and inverse currents, the exhaustion 
 of nerves by continued stimulation, and their recovery by 
 
$8 GALVANI AND GALVANISM. 
 
 repose, together with many other similar conditions, were 
 indispensable stages in the progress of discovery, and were 
 the fruit of many intermediate investigations. But each 
 series depended, for the possibility of its existence, on an- 
 other which had gone before ; and they all had their origin, 
 in a continuous line of descent, from the experiments of 
 1789, in Galvani's laboratory at Bologna. 
 
LECTURE II. 
 
 BUFFON AND BONNET IN THE EIGHTEENTH CENTURY. 
 
 Mr. President and Gentlemen, — I shall ask your atten- 
 tion in this evening's lecture to two remarkable phases of 
 physiological doctrine which once held a conspicuous place 
 in the world of science; namely, Buffon's theory of Or- 
 ganic Molecules, and Bonnet's theory of the Inclusion of 
 Germs. Notwithstanding that both are now so obsolete 
 that perhaps the majority of my hearers will hardly recall 
 their meaning, they were formerly considered of sufficient 
 importance to be test questions in the controversies of the 
 period, and they are fair examples of the fluctuating esti- 
 mate to which such subjects are liable at different times. 
 
 It sometimes happens, that, in searching the annals of 
 medicine, we find allusions to systems and theories which 
 have so far gone out of vogue that we know them only by 
 name. They are no longer part of our scientific doctrines ; 
 and they have so little present value or significance, that 
 we seldom spend the time even to weigh their merits or 
 defects. And yet these systems once had their day. They 
 were prominent topics of discussion and interest ; and they 
 divided medical opinion between the views of antagonistic 
 parties, or carried with them the scientific world in a tem- 
 porary enthusiasm of acceptance and admiration. They 
 
 39 
 
40 BUFFON AND BONNET 
 
 were often originated by men of learning and ability, and 
 owed much of their success to the superior talent of their 
 authors. They were usually ambitious in design, and se- 
 ductive to the imagination. They claimed to open a wider 
 field of knowledge, and to unlock the secrets of nature by 
 , some new formula that should dispense with the older and 
 slower methods of plodding investigation. So long as they 
 held out this prospect, they stimulated the hopes and at- 
 tracted the interest of all. But after a time it appeared 
 that the anticipations which they excited were not fulfilled, 
 and that their promised results failed of realization. Then 
 the theories themselves began to lose in importance ; and, 
 once started on the downward road, they receded more and 
 more rapidly from view, until they finally passed out of 
 sight and out of mind. They vanished into the limbo of 
 departed spirits ; and, if they ever show themselves at the 
 present day, it is only to gratify a momentary curiosity as 
 the relics of thought and opinion in former times. Like 
 unsubstantial shadows, they flit across the pages of a for- 
 gotten literature, and the glimpses that we catch of them 
 here and there are the only traces of their existence in the 
 history of the past. 
 
 One of these phantoms, alive and flourishing a hundred 
 years ago, was Buffon's theory of Organic Molecules. 
 
 Buffon was a remarkable instance of a man of splendid 
 but temporary reputation. His ability commanded the 
 attention of his contemporaries, and enlisted their interest 
 and co-operation for natural history as no modern writer 
 had done before. His immediate successors were fond of 
 comparing him with Aristotle and Pliny ; and, if we take 
 their estimate of his reputation, there have been few men, 
 either in science or literature, who ever acquired so great 
 a popular renown. He was a member jof the French 
 
IN THE EIGHTEENTH CENTURY. 4 1 
 
 Academy, of the Academy of Sciences, of the Royal So- 
 cieties of London and Edinburgh, and of the Academies 
 of Berlin and Bologna. He was created a count by Louis 
 XV., and was for forty years Superintendent of the Garden 
 of Plants, which he more than doubled in extent, and 
 where his statue was erected while he was yet alive. His 
 great work on natural history was received as an authority 
 from the date of its publication. Most of the European 
 potentates sent him specimens for his museum or compli- 
 mentary messages ; strangers from abroad thought it a 
 privilege to see him ; and among the visitors at his country- 
 house were Thomas Jefferson and the Prince of Prussia. 
 
 Notwithstanding this extraordinary success, Buffon's 
 qualities could not secure a lasting reputation. He excited 
 the enthusiasm of his readers by his eloquence and origi- 
 nality, but he did not give them much real instruction. 
 This deficiency was felt even by his friends. Vicq d'Azyr, 
 who pronounced his eulogy in the French Academy, and 
 who calls him " one of the lights of the age, and an orna- 
 ment to his country," says that he often "compels ad- 
 . miration, without convincing the judgment." According 
 to Moreau, he "supplemented, by the brilliancy of his 
 imagination, the imperfections of his knowledge," and 
 showed himself " more remarkable for boldness of concep- 
 tion than for precision of ideas." There can be no doubt 
 that he did much, in his own time, to popularize natural 
 history among the educated and influential classes ; but it 
 was rather as an intellectual entertainment than a scientific 
 pursuit, and his works are now nearly destitute of value for 
 any purposes of reference or exact information. 
 
 It appears that Buffon's style as a writer was one of his 
 principal charms for the readers of that day, and formed a 
 large element in his success. It had a sort of poetic 
 
42 BUFFO N AN'D BONNET 
 
 splendor, that would be thought quite inadmissible at pres- 
 ent in a scientific work, and sometimes will hardly bear 
 translation without a close approach to puerility; but at 
 the period when he wrote, and in his hands, it magnified 
 his subject and made an impression upon his readers. He 
 often adopts this lofty tone at the opening of a chapter, 
 and nearly always employs it for descriptive passages. He 
 introduces the horse as " this proud and impetuous animal, 
 , the noblest conquest ever made by man, his companion in 
 Uhe fatigues of war and in the glory of combats." The 
 ' 'elephant, he says, " makes the earth tremble beneath his 
 footstep, uproots trees from the soil, and with one thrust 
 of his body will batter down a wall." Buffon took great 
 pains to cultivate and perfect this style. They say he 
 would often repeat certain passages aloud, or get his friends 
 to do so with himself for an audience, to enjoy the sound 
 of his swelling sentences, and perhaps make some improve- 
 ment in their construction. One of the extracts which he 
 was especially fond of hearing in this way was his delinea- 
 tion of the feelings of the first man, when just awakened 
 to consciousness and vitality. The newly created being is 
 supposed to be telling his own story, as follows : ' — 
 
 " I well remember that instant of mingled joy and anx- 
 iety, when I felt for the first time my extraordinary exist- 
 ence. I knew not what I was, where I was, nor whence 
 I came. I opened my eyes. What an overflow of sen- 
 sation ! The daylight, the celestial vault, the green 
 earth, the crystal transparency of the waters, all attracted 
 me, excited me, and gave me an inexpressible sense of 
 enjoyment." And so on, for seven or eight consecutive 
 pages. 
 
 Another favorite passage was his picture of an Arabian 
 
 ' CEuvres Completes de Buffon. ame Edition. Paris, 1819. Tom. x. p. 358. 
 
IN THE EIGHTEENTH CENTURY. 43 
 
 desert, introduced apropos of the natural history of the 
 camel.' 
 
 " Imagine," he says, " a region without verdure or moist- 
 ure, a blazing sun, the sky always arid, plains of sand, and 
 mountains still more parched, where the eye searches in 
 vain for any trace of a living creature ; a land .lifeless and, 
 as it were, stripped by the winds, where nothing is to be 
 seen but dead bones, scattered pebbles, and rocks standing 
 or overturned ; a barren desert, where the traveller never 
 finds a shady resting-place, where he has no companion- 
 ship, nor any thing to remind him of life in nature ; abso- 
 lute solitude, a thousand times more frightful than that of 
 the forest, since even trees are living beings for the man 
 who is there alone. In these void and measureless regions, 
 more isolated, denuded, and desolate than any other, the 
 empty space seems to enclose him like a tomb. The light 
 of day, more gloomy than the shades of night, only serves 
 to disclose his helplessness and destitution. It shows him 
 the horror of his situation by enlarging before his eyes the 
 boundaries of vacancy, and shuts him out from the habita- 
 ble world by stretching around him an abyss of immensity 
 which he can never hope to cross." 
 
 The satisfaction which Buffon felt in these descriptions 
 does not seem to have been diminished in any way by the 
 fact that he had never seen an Arabian desert, and that 
 his story of the first man was entirely imaginary. 
 
 BufEon's "Natural History" was a work of very exten-' 
 sive design. It included an explanation of the structure 
 and physical geography of the globe, the nature of man and 
 animals, a general view of animals, vegetables, and minerals, 
 the functions of nutrition and reproduction, an account of 
 the varieties of the human race, and the different species 
 
 ' CEuvres Completes, torn. xv. p. 336. 
 
44 BUFFON AND BONNET 
 
 of birds and quadrupeds,' with a description of specimens 
 in the Royal Museum. 
 
 He had a theory of the planetary system, which was one 
 of his favorite doctrines, and which occupies the greater 
 part of his first volume. He believed that the planets were 
 originally a part of the solar sphere, from which they had 
 been struck off at some time by the shock of a comet in 
 collision with the sun.^ The materials of different densi- 
 ties, propelled under this impulse with different velocities, 
 he supposed would naturally collect into masses at corre- 
 sponding distances from their starting-point, and so give 
 rise to a series of planets, moving in successive orbits. 
 Their axial rotation was accounted for by the obliquity 
 with which the comet struck the sun, and the consequent 
 twirling motion imparted to its detached portions. 
 
 Wild as this hypothesis sounds when -stated by itself, it 
 was advocated by its author with much force and ingenuity. . 
 Even mathematics came in for a share in its support, and 
 it was fortified with arguments from the doctrine of proba- 
 bilities. As all the planets move round the sun from west 
 to east, and nearly in the same plane, they must all have 
 been set in motion, according to Buffon, at the same time 
 and by a single impulse. Otherwise, the chances would be 
 as 64 to I that the six planets then known would not all 
 move in the same direction, and as 7,962,624 ^ to i that all 
 their orbits would not be within seven and a half degrees 
 of the same plane. He extended the calculation still far- 
 ther, — to the size, distance, and density of the different 
 planets, and to the relation in each between its density and 
 the rapidity of its orbital motion. The figures, did not all 
 
 ' CEuvres Completes, torn. i. p. 151. 
 
 ^ This was in 1750, when Saturn was supposed to be the outermost planet of the 
 solar system. If the author had included in his calculations Uranus and Neptune, he 
 might have made the chances in favor of his theory as 4,586,471,424 to i. 
 
IN THE EIGHTEENTH CENTURY. 45 
 
 come out exactly right ; but in the case of Jupiter and Sat- 
 urn the theoretical and actual proportions were very nearly 
 alike, and the author observes with much satisfaction that 
 "we cannot often obtain, in matters of pure conjecture, so 
 close an approximation to reality as this." 
 
 But the most remarkable production of Buff on' s genius 
 was his system of organic molecules, with its associated 
 theories of nutrition and reproduction. According to this 
 view, the bodies of all living creatures, animal and vege- 
 table, were composed of minute particles, differing in kind 
 and configuration, but all possessing the general character 
 of vital endowment. These were the organic molecules. 
 As we call a compound group of hydrogen and oxygen 
 atoms a molecule of water, or one of carbon, hydrogen, and 
 oxygen a starch or glucose molecule, so Buffon seems to 
 have imagined a still more complex molecule, having thej 
 properties of organic life. These molecules, when associ- 
 ated in the form of an organized body, gave to each part 
 its specific character, and thus provided for the physio- 
 logical activity of the whole. But they were themselves 
 indestructible, and contained in their own substance the 
 essential principle of vitality. When the animal or plant 
 died and was decomposed, its organic raolecules were at 
 once ready to assume new combinations. When one ani- ' 
 mal fed upon another, or an animal upon a plant, the or- 
 ganic molecules of the creature used as food passed into 
 the tissues of that which devoured it ; and when an animal, 
 in decomposing, enriched the soil and fed vegetation, its 
 organic molecules were absorbed into the structure of the j 
 growing plant. Thus these molecules represented the liv- 
 ing elements of the material world. Their quantity was 
 never either increased or diminished ; they only passed 
 from one form of combination to another, always transfer- 
 
46 BUFFON AND BONNET 
 
 ring their activity from the old organisms to the new. 
 Consequently there was no such thing as destruction of 
 life in nature, but only continual changes in its distribu- 
 tion. The organic molecules were an exhaustless reservoir 
 of vitality, from which all living beings took their origin, 
 and into which they all again returned. 
 
 But nutrition and generation require something more 
 than the mere existence of organic molecules. For, even 
 supposing these vitalized particles to be present in full abun- 
 dance and variety, how could they be arranged in proper 
 order within the plant or animal, so as to form its different 
 organs or enable it to reproduce its like .' This want was 
 supplied by Buffon's celebrated- idea of interior moulds. It 
 is not easy to say exactly what he meant by this expression, 
 except that it was something capable of arresting the mole- 
 cules, and placing them in a certain combination. " In the 
 same way," he says, "that we have moulds for giving to 
 the outside of things any form we choose, suppose that 
 nature can produce moulds which will determine, not only 
 the external configuration, but also the internal structure 
 of bodies formed in them." 
 
 Most readers will perhaps say that this definition of 
 interior moulds is only an analogy, and does not include 
 any intelligible idea of their construction. Buffon himself 
 seems partly conscious of this, and makes a rather, labored 
 and metaphysical defence of the term, to show that there 
 is nothing in it contradictory. However that may be, the 
 " interior mould " is something which belongs to the entire 
 body and also to each of its separate parts. The whole 
 body is a mould which determines the position and ar- 
 rangement of its different organs. Each organ and each 
 part of an organ, when supplied with organic molecules 
 from the food, selects those which are like its own, and 
 
IN THE EIGHTEENTH CENTURY. 47 
 
 rejects the rest ; while it arranges the incoming molecules 
 in proper order, and incorporates them with its substance, ' 
 still preserving its original form and texture. In 'this way 
 the body is nourished and grows, not by addition to its 
 exterior, but by the intimate penetration and intus-suscep- 
 tion of appropriate molecules throughout its mass ; and all 
 by means of its " interior moulds." 
 
 The mysterious phenomena of reproduction were fully 
 explained by the aid of organic molecules and interior 
 moulds. This explanation was even the simplest in cases 
 which we usually consider the most wonderful ; as where 
 plants, worms, or polypes reproduce and multiply, without 
 sexual generation, by division or budding. Suppose, in a 
 polype, the organic molecules to be arranged throughout in 
 the form of minute polypes, just as a cube of salt may be 
 made up of an indefinite number of smaller cubes ; then 
 any part of such an organism, when separated from the 
 rest, will reproduce an entire polype, because it already 
 contains the whole of it in miniature. Something similar 
 takes place in animals or plants which multiply by bud- 
 ding. In them the organic molecules absorbed with the 
 food are distributed in due proportion until every part has 
 received its full supply. After that, the surplus molecules 
 are sent back from the different organs and collected in 
 some particular locality, where they form a composite mass 
 representing the materials of the whole body. Such a 
 mass is a bud; and when separated from its stock, and 
 placed where it can absorb nourishment for itself, it of 
 course grows into an organism like its parent, because it is 
 composed of the same kind of molecules, arranged in the 
 same order and in the same proportions. 
 
 In sexual generation, like that of the higher animals, the 
 process is more complicated. Here, again, every part of 
 
48 BUFFON AND BONNET ■ 
 
 the body absorbs the organic molecules appropriate to 
 itself, and moulds them into the substance of its own tex- 
 ture. But the excess of material, not required for the 
 nourishment of the organs, and returned from them as 
 superfluous, appears in the form of a liquid, and is de- 
 posited in a special reservoir. This liquid, made up of con- 
 tributions from every part of the body, is the seminal fluid. 
 It is a mingled organic extract of the entire frame, and thus 
 contains all the materials necessary for reproduction. Its 
 place of deposit is in the vesiculse seminales. 
 
 The extreme activity of this seminal fluid, the concen- 
 trated essence of the animal organism, is proved by the 
 formation of the spermatic animalcules. According to 
 Buffon, these are not oiriginal or essential ingredients of 
 the seminal fluid, but a product of its restless vitality, an 
 incidental form in which its generative power is exhibited.' 
 They represent the first assemblage of its organic mole- 
 cules, as combined into moving particles large enough to 
 be visible by the microscope. 
 
 But the female also produces a seminal fluid in the same 
 manner and with the same general qualities as the male. 
 Both fluids, male and female, contain all the elements com- 
 mon to either sex. The only difference between them is, 
 that, each fluid being a special extract of the body from 
 which it comes, that of the male contains molecules repre- 
 senting the male peculiarities, that of the female those repre- 
 senting the female peculiarities. Buffon entirely rejects 
 the doctrine that viviparous animals produce by means of 
 eggs. For him, the ovaries are testicles, the Graafian folli- 
 cles are reservoirs of nutritious lymph, and the corpora 
 lutea are glandular structures, which produce the female 
 seminal fluid by a process of filtration.^ 
 
 » CEuvres Completes, torn. ix. p. 335. ^ Ibid., p. 345. 
 
IN THE EIGHTEENTH CENTURY. 49 
 
 Thus BufEon accounts for reproduction in a very simple 
 manner. Generation is only, in a higher degree, the act of 
 nutrition, operating with the surplus of nutritive material. 
 A mixture of the male and female seminal fluids contains 
 all the organic elements of both sexes, and therefore repre- 
 sents the species. In the uterine cavity it finds its appro- 
 priate nidus and nourishment, and grows into an organism 
 like that from which it came. The theory was supported 
 by abundance of pfoof, for it explained to a charm most of 
 the important phenomena of generation, ist. During in- 
 fancy and childhood there is no power of reproduction, 
 because all the organic molecules are taken up by the 
 growing tissues : it is only after puberty, when the body 
 has acquired its full growth, that there is a surplus of or- 
 ganic material, to be filtered through the testicles in the 
 form of seminal fluid. 2d, The young child or animal 
 usually resembles both its parents, because its substance is 
 derived from both the male and female seminal fluids. 3d, 
 Creatures of small size, like insects, mice, and guinea-pigs, 
 have a numerous progeny, because the demands of nutri- 
 tion are easily satisfied, and there is a large superfluity left 
 for reproduction. But those of greater bulk, such as man, 
 the horse, the elephant, produce only a single young one 
 at a time, and at long intervals, since the nourishment of 
 their own bodies takes up most of the organic molecules 
 of the food. All these facts were plainly in accordance 
 with the new system. 
 
 Indeed, the only difficulty about Buffon's theory, if it is 
 not a contradiction to say so, was that it made the matter 
 too easy. If the seminal fluid of the male contains all the 
 organic molecules necessary to make an embryo, why does 
 it not make one t Why should not the male be self-pro- 
 'ducing .' and why should not the female, on the other hand. 
 
50 BUFFON AND BONNET 
 
 have a progeny of little females, from her own seminal 
 fluid, without requiring any thing further ? According to 
 the theory of organic molecules, every adult animal pro- 
 duces a fluid capable of generating young. But, in point 
 of fact, the female must also receive the influence of the 
 male ; and, without the concourse of the other, each sex 
 remains barren. 
 
 This is the great difficulty in Buffon's way ; and, to do 
 him justice, he does not try to conceal or evade it, but 
 struggles with it manfully for sixteen octavo pages. The 
 reader almost feels a sympathy for him, when his system of 
 reproduction, after running so smoothly everywhere else, 
 is arrested by so bulky an obstacle as the fact of sexuality. 
 His explanation is full of ingenious hypotheses ; but it is 
 veiy complicated, and leaves in the chain of evidence so 
 many gaps and contradictory possibilities, that it is hardly 
 worth while to remember it. Nevertheless, the author 
 thinks too well of the system to have his faith in it shaken 
 by one or two imperfections. The main part of it, he says, 
 he has " proved by so many facts and arguments, that to 
 doubt it is hardly possible." He does not doubt it himself ; 
 and he avows that he " entertains no uncertainty whatever 
 as to the basis of the theory, after careful scrutiny of its 
 principles and the most rigorous estimate of its conse- 
 quences and details." 
 
 Buffon's system has its widest extension and most 
 splendid success in the dim regions of equivocal and 
 spontaneous generation. His organic molecules are the 
 genuine repositories of life, the interior moulds of par- 
 ticular organisms being only the means of arranging them 
 in special forms. And when, by the death of an animal 
 and the decomposition of its body, its organic molecules 
 are released from the constraint of their interior moulds, 
 
IN THE EIGHTEENTH CENTURY. $1 
 
 they are set at liberty, living and active as ever, to be dis- 
 seminated in any direction where chance may carry them. 
 In this condition they are the universal seed of nature; 
 without any character of specific organization, but contain- 
 ing all the prolific force of the bodies from which they 
 came. After a time they are absorbed by some other 
 mould, animal or vegetable, into which they transport their 
 own indestructible qualities of nutrition and life. But 
 during the interim, after leaving the old organism and 
 before their incorporation into the new, they form by their 
 re-union a multitude of living structures which do not 
 belong to any of the ordinary or recognized species in 
 nature. Such are the moving corpuscles of the seminal 
 fluid, the microscopic fungi and infusorial animalcules of 
 organic solutions, and, in their larger varieties, the eels 
 of starch-paste and vinegar, and even earth-worms, mush- 
 rooms, and entozoa. All these creatures come by spon- 
 taneous generation. They are the connecting link in 
 nature between the simple organic molecule on the one 
 hand, and the complete animal or plant on the other. This 
 exuberant force of production is always in activity. Not- 
 withstanding the death of any number of existing creatures, 
 the total quantity of life on the globe cannot be diminished 
 even for a moment ; for it continues uninterrupted in the 
 organic molecules, which pass and repass from the animal 
 to the vegetable, and from the vegetable to the animal, or 
 produce in the interval an endless variety of spontaneous 
 generations. 
 
 No doubt, Buffon was in love with his system, and ad- 
 mired it for its own sake. Still he had a fair share of what 
 Condorcet calls the "sentiment of his own superiority," 
 and ends one of his chapters in a strain that sounds, at 
 this day, rather exalted. " I will add nothing more," he 
 
52 BUFFON AND BONNET 
 
 says, " to these reflections. To be accepted, or even to be 
 comprehended, they require a profound acquaintance with 
 nature, and complete freedom from prejudice; so that, for 
 the majority of my readers, a longer explanation would be 
 insufficient, and, for those who can understand me, it would 
 be superfluous." 
 
 When Buffon's work 'appeared, it attracted at once 
 the curiosity and applause of the public. The reviewers 
 praised it as " an honor to both the age and the nation. "' 
 Hume said that its author " gave to things no human eye 
 had seen a probability almost equivalent to proof;" and 
 Needham declared that his investigations on the seminal 
 fluid would be a subject of admiration "for centuries to 
 come." All his readers, however, were not of that opinion. 
 There were some who did not accept the doctrines of the 
 book, and who feared that its popularity might have a bad 
 effect. Buffon's high position, his magnificent style, and 
 his confident tone of assertion^ alarmed his adversaries, 
 and made them dread his influence on the public mind. 
 His theory, they said, was " filled with dazzling paradoxes, 
 as disastrous to the principles of science as the mines of 
 a skilful engineer to the solid ramparts of a fort." This 
 diffeirence led to a warm discussion. The Abbe de Lignac 
 wrote an anonymous treatise against Buffon's work, under 
 the title of " Letters to an American," ^ where he criticised 
 the system of moulds and molecules, and said, that, instead 
 of describing natural objects, it contained only "the philo- 
 sophical dreams of M. de Buffon." BufEon's friends, on 
 the other hand, denounced the " American Letters " as a 
 lampoon. They accused de Lignac of having written it 
 
 ■ Journal des Savans. Paris, Octobre, 1749. 
 
 2 Lettres i. un Ameriquain, sur I'Histoire Naturelle de M. de Buffon. Hambourg, 
 1751. 
 
IN THE EIGHTEENTH CENTURY. 53 
 
 out of envy, and to punish Buffon for not showing more 
 respect to his friend R6aumur. Deslandes called the 
 book an imposture, because it was entitled " Letters to an 
 American," when it had not been written, in the form of 
 letters, to anybody ; and because the title-page bore the 
 imprint of Hambourg, though it was really printed at 
 Paris. " That makes no difference," replied de Lignac : 
 "the only title-page that can be called an imposture is 
 one that promises something the book does not contain ; 
 like a Natural History, for instance, made up of disjointed 
 and extravagant systems, without any thing natural about 
 them." 
 
 Buffon's critics were especially dissatisfied with the 
 organic molecules of the seminal fluid, and their wonderful 
 capacity for producing an embryo. " If these molecules," 
 they said, " are indifferently the elements of a plant, a man, 
 a dog, or a polype, how can they combine to make either .' 
 We might as well go back to Epicurus and his atoms." 
 One of them was asked, by an admirer of Buffon, which he 
 would rather be, — the author of the " Histoire Naturelle," 
 or that of the " Lettres Am^ricaines." He replied that he 
 would rather be an organic molecule, because then he would 
 have more intelligence than either of them. Buffon held 
 his own against these attacks without making any direct 
 reply. His literary talent alone was almost enough to 
 secure him the victory ; and, if his opponents denied the 
 truth of his theory, they generally had nothing better to 
 offer in its place. 
 
 The only investigations at that time, which seriously 
 threatened Buffon's system, were those of Haller on 
 fecundation and development. They first appeared in 
 1753, four years after Buffon's first publication. Haller 
 had examined the ovaries of sheep both before and after 
 
54 BUFFON AND BONNET 
 
 impregnation, and observed the condition of the Graafian 
 follicles and corpora lutea. Since corpora lutea, accord- 
 ing to Buffon, were glands, for producing a seminal fluid, 
 they must, of course, be formed before impregnation, and 
 could only discharge their fluid at the time of conception. 
 Haller declared that there were no corpora lutea in the 
 ovaries during the period of heat, nor immediately after 
 conception, at which time there was nothing to be seen 
 but a simple orifice leading into a ruptured follicle. The 
 glandular structure of the corpus luteum was only formed 
 some days afterward, and therefore could not have furnished 
 any thing ess^ential to conception.' We now know the 
 accuracy of these observations by Haller, and can hardly 
 understand how those of Buffon should have been so pre- 
 posterously incorrect. But at that time it was difficult to 
 decide between them. Both were men of high scientific 
 position, and the system of organic molecules was too 
 promising and seductive to be surrendered at the first 
 attack. 
 
 But as time went on, it began to suffer from its own 
 defects. After thirty or forty years' trial, its promises had 
 not produced any thing, its obscurities had not been cleared 
 up, and the organic molecules were still as hypothetical as 
 ever. One of Buffon's tenets for explaining reproduction 
 by division was, that the simpler organisms, like plants and 
 ' polypes, were composed of particles in the form of their 
 own miniature ; and he had argued at great length that this 
 kind of structure, if we only thought so, was as simple as 
 any other. Malesherbes^ finally concluded that it would 
 be of no use to think so, because the thing was impossible. 
 " To be convinced of this," he says, " let any one try to 
 
 ' Histoire de I'Acad^mie Royale des Sciences. Ann^e 1753, p. 134. 
 * Observations sur I'Histoire Naturelle de Buffon, Paris, 1798. 
 
IN THE EIGHTEENTH CENTURY. 55 
 
 draw a picture of this pretended polype, entirely made up 
 of similar polypes ; or let him get a quantity of little wooden 
 or ivory figures in the form of polypes, and then see whether 
 he can put them together in any way so as to make an 
 entire polype of the same shape. I defy him to do so." 
 
 Buffon's interior moulds had no better luck in the end. 
 When it came down to genuine matter of fact, no amount 
 of verbiage could make it plain what sort of things they 
 were, nor how they operated. Malesherbes declared that 
 the very idea of a mould is that of something which acts by 
 its surfaces ; and that consequently the hypothesis of inte- 
 rior moulds is a mere metaphysical subtlety, without any 
 real application. " To make use of interior moulds, there- 
 fore, for explaining the process of nutrition or development, 
 is to solve one difficulty by another : it accounts for one 
 thing by the supposition of a second no more intelligible 
 than the first. The truth is, it does not really give any 
 explanation at all : it only answers, like the doctor in Moli- 
 ere. Opium facit dormire quia habet facultatem dormi- 
 tivam" 
 
 Another cause of decline for Buffon's system, toward the 
 end of the last century, was the progress of opinion in 
 regard to spontaneous generation. At that time there was 
 much investigation on this subject, especially as to the 
 infusorial animalcules. Needham and Spallanzani were 
 the principal disputants in this field, and attracted to it, for 
 some years, the attention of the scientific world ; the result 
 being, at last, a general conviction that Spallanzani's experi- 
 ments had destroyed the hypothesis of spontaneous genera- 
 tion, at least for the infusoria. Buffon's system, therefore, 
 diminished in importance, because this mysterious depart- 
 ment of reproduction, which it had explained so well, no 
 longer needed explanation. It thus lost one of its strongest 
 
56 BUFFON AND BONNET 
 
 claims to support ; and, without being actually disproved, 
 it was discredited to an extent which must have seriously 
 impaired its scientific status. 
 
 Finally it received its death-blow, in 1827, from de 
 Baer's discovery of the ovule in the ovarian follicle of mam- 
 malians." 
 
 De Graaf had supposed, when he first described the ovari- 
 an follicles, a hundred and fifty years before, that they were 
 really eggs ; and this view was widely accepted. The ovaries 
 of mammalians, like those of fishes and birds, were regarded 
 as clusters of eggs held together by intervening tissue. But 
 it was not easy to demonstrate, in man and quadrupeds, the 
 discharge of these supposed eggs from the ovary. No 
 observer had ever succeeded in finding one of them sepa- 
 rated from its ovarian connections ; and the earliest ovum 
 discoverable in the uterus, or Fallopian tube, was, of course, 
 considerably smaller than the ripe follicle in the ovary. 
 This threw a doubt over the doctrine of de Graaf, and left 
 room for Buffon's assertion that there were no such things 
 as eggs in the mammalian female ; that her so-called ovaries 
 were testicles, as much so as those of the male ; and that 
 she produced a seminal fluid composed of organic molecules 
 similar to his. 
 
 This view was so interwoven with Buffon's whole system, 
 that one could hardly exist without the other. And when 
 the microscopic ovum and its mode of exit from the ovary 
 were at last fully brought to light, so that any one could 
 see them when he chose, the discussion necessarily came 
 to an end. The female testicles and seminal fluid, with 
 their glandular corpora lutea, no longer had a place in 
 court : every thing connected with them shared in the col- 
 lapse ; and the entire company of organic molecules, repro- 
 
 ' K. E. von Baer: De Ovi mammalium et hominis genesi. Lipsiae, 1827. 
 
IN THE EIGHTEENTH CENTURY. 57 
 
 ductive extracts, composite organisms, and interior moulds, 
 disappeared together, like actors at the end of a play. 
 
 Another set of ideas, once in high repute but now long 
 obsolete, are those of Bonnet on the " Inclusion of Germs." 
 
 Bonnet was of a wealthy and influential family in Geneva, 
 where he passed the whole of his life, engaged in the study 
 of natural history and kindred subjects. He became widely 
 known for his attainments in this direction, and was con- 
 nected with nearly all the learned societies of Europe. 
 He was the friend and correspondent of R6aumur, Haller, 
 Spallanzani, Trembley, and de Saussure. Spallanzani com- 
 municated to him in manuscript, for perusal and advice, his 
 own researches on the generation of infusoria ; and, when 
 the volume appeared, he ■ printed, as part of it, Bonnet's 
 letters in reply.' 
 
 The personal character of Bonnet had traits of superior 
 excellence, and secured him a large share of attachment 
 and esteem. His disinterestedness and modesty, in regard 
 to his own opinions, were well known, and were often the 
 subject of eulogy. His own discoveries in entomology were 
 of acknowledged merit ; but he attributed them mainly to 
 the teaching of Reaumur, because he had been inspired by 
 the example and encouragement of this master, under whom 
 he felt " proud to enroll himself as a pupil." Spallanzani 
 calls him the "Philosopher of Geneva" and the "sublime 
 author of the ' Contemplation of Nature.' " His first pub- 
 lications appeared in 174S, and were followed by others at 
 various dates until 1770, after which they were collected in 
 a series of eighteen volumes.^ 
 
 Bonnet presented the curious spectacle of a man under 
 
 • Spallanzani : Oposcoli di fisica anlmale et vegetabile. 
 
 « Ch. Bonnet: CEuvres d'Histoire Naturelle et de Philosophie. Neuchatel, J 779. 
 
S8 BUFFON AND BONNET 
 
 the varying influence of two opposite tendencies, — at one 
 time an exact and painstaking observer of nature ; at an- 
 other, an irresponsible wanderer in the vaguest of specula- 
 tions. His earliest scientific work was an experimental 
 investigation on the reproduction of aphides, by which he 
 first demonstrated with certainty the non-sexual viviparous 
 propagation of these insects.' It is hardly possible to 
 imagine a more thorough, direct, and conscientious method 
 than that adopted by Bonnet in these observations. He 
 took the young aphis just expelled from the body of its 
 parent, placed it upon a sprig of fresh leaves stuck in a pot 
 of earth and covered with a bell-glass, and then watched 
 his solitary prisoner for twenty-one days, until it had grown 
 to maturity, and had produced, without fecundation, ninety- 
 five young ones. During this time he kept exact records 
 of the insect's moulting, and also of the new births, most 
 ,of which took place under his own eye. He repeated the 
 trial with aphides of different species, and with those which 
 had themselves been produced in captivity ; and he suc- 
 ceeded in raising them in this way, without fecundation, for 
 eight successive generations. For these observations he 
 received the honor of an election as Correspondent of the 
 French Academy of Sciences. He also made valuable 
 contributions to natural history on the multiplication of 
 aquatic worms by division, on the growth of plants, on the 
 function of leaves, and on the habits of insects. 
 
 On the other hand, he constructed, out of his own medi- 
 tations, a graduated system of things visible and invisible, 
 which he called the " Scale of Being," and which formed 
 the subject of one of his later works, published under the 
 title "Contemplation de la Nature." It embraced the 
 structure of the entire universe, from the simple elements 
 
 ' CEuvres de Bonnet, torn. i. p. 19. 
 
IN THE EIGHTEENTH CENTURY. $9 
 
 of inorganic matter to the " celestial hierarchies " of other 
 worlds. According to this system, there are no gaps or 
 sudden variations in nature, but only a continuous series 
 of combinations and modifications in ascending grade. 
 Every thing is immediately connected with that which pre- 
 cedes and with that which is to follow. At the beginning 
 of the volume there is inserted, for the reader's convenience, 
 a printed table exhibiting the regular succession of natural 
 objects, from gaseous substances up to man. The inor- 
 ganic elements, in various grades of combination, lead to 
 the composite earths, sulphurs, and metallic bodies ; thence, 
 through the vitriols or metallic salts, to ordinary saline 
 substances in crystalline form ; and thence to compound 
 rocks of heterogeneous structure, like granite and sand- 
 stones. Immediately above these are rocks, like slate, talc, 
 and asbestos, which exhibit a laminated or fibrous texture, 
 and which may therefore be considered as " the connecting 
 link between inorganic and organic solid bodies." 
 
 This point is especially important in Bonnet's scheme, 
 for it marks the passage from dead matter to living organ- 
 isms. It is not altogether what its author could wish ; but 
 he makes the best of it by quietly putting the burden of 
 proof on posterity. "It must be acknowledged," he says, 
 " that the transition here is not quite so perfect as in many 
 other cases. It looks as though nature in this instance 
 had made a leap. But the gap will undoubtedly be filled 
 up as our knowledge increases in precision and extent." 
 
 Once fairly started among organized structures, the scale 
 rises easily through corals, lichens, and mushrooms, to 
 plants in general ; through the sensitive plant to animals ; 
 from insects to snails, serpents, eels, and fish ; through fly- 
 ing-fish to birds ; from birds to bats and quadrupeds ; and 
 so on, to monkeys, apes, and man. But this extended 
 
6o BUFFON AND BONNET 
 
 gradation is not enough for Bonnet. He has also the " Celes- 
 tial Hierarchies " and the " Gradation of the Worlds ; " 
 some of which, he believes, are as superior in physical and 
 moral organization to our earth as man is above the ape. 
 
 The frontispiece to Bonnet's work is an engraved por- 
 trait of himself, taken, as he tells us, when he was " plunged 
 in deep meditation on the restitution and perfectibility of 
 living creatures." It renders, he thinks, his "reflective 
 expression " with much success ; and it is certainly fortu- 
 nate that the artist saw him just when he happened to be 
 meditating on so abstruse a subject: 
 
 Bonnet's theory of reproduction, or the "Inclusion of 
 Germs," appears mainly in his work entitled " Consi- 
 derations sur les Corps Organises," with some additional 
 amplifications in the " Contemplation de la Nature." His 
 thoughts were turned in this direction partly by Trem- 
 bley's recent discovery of the multiplication of fresh-water 
 polypes by division, and partly by his own observations on 
 the reproduction of aquatic worms and aphides. He was 
 further strengthened in his opinion by Haller's observa- 
 tions, which appeared in 1758, on the formation of the 
 chick in the fowl's egg. 
 
 There were, about that time, three different views enter- 
 tained as to the nature of sexual generation, — 
 
 First, The spermatic animalcules, one or more in num- 
 ber, were arrested in the uterus, and there became devel- 
 oped into embryos. According to this view, the male 
 parent furnished the germ, the female only providing for 
 its care and nourishment. 
 
 Second, The seminal fluids of both sexes, when mingled 
 together, produced the embryo, de novo, by a mutual 
 arrangement of their organic particles. This was the doc- 
 trine of Buffon, and attributed an equal and similar action 
 to both parents. 
 
IN THE EIGHTEENTH CENTURY. 6 1 
 
 Third, The germ pre-existed in the ovary and egg of the 
 female, and was only stimulated to further development 
 by the seminal fluid of the male. 
 
 Bonnet accepted the third of these doctrines. He be- 
 lieved in the pre-existence of germs, but he gave to the 
 idea a much wider extent and significance. The germ, as 
 he understood it, was not only a structure capable of being 
 developed into a living creature, but actually contained, 
 within itself and ready formed, all the parts of the future 
 organism. These parts were exceedingly minute, delicate, 
 and transparent ; but they nevertheless existed, though as 
 yet imperceptible to the senses. It was only their small 
 size, their softness and transparency, which prevented 
 their being seen. After impregnation they grew larger, 
 more consistent, and more opaque, and then first became 
 recognizable as the organs of the embryo. These organs, 
 accordingly, were not things of new formation. They 
 only showed plainly, at a certain period of development, 
 what had previously existed in invisible form. The author 
 extended this doctrine without hesitation to its farthest 
 limits. For him, every seed contains a plant in miniature. 
 In an animal germ, every organ and tissue, without excep- 
 tion, is already present, — the heart, the vessels, the liver, 
 the kidneys, the intestine, the nerves, and the brain. Con- 
 sequently there is no such thing as generation, if by that 
 we understand the production of a new being, or even of a 
 new organ. What appears to be such is only the develop- 
 ment of something that was in existence beforehand. 
 
 These views were adopted by some, and rejected by 
 others ; the physiological theorizers of the day dividing into 
 two parties, known as the epigenesists and the evolutionists. 
 The epigenesists were those who believed, like Buffon, that 
 the embryo was a new formation, produced by the union 
 
62 BUFFON AND BONNET 
 
 of molecules and the successive organization of different 
 parts. The evolutionists,' on the other hand, maintained, 
 with Bonnet, the pre-existence of germs, and insisted that 
 nothing in the embryo was newly formed, but only enlarged 
 and solidiiied by development. 
 
 These notions were sustained in some degree by the 
 discoveries of Haller in the incubation of the fowl's egg- 
 Haller had studied the development of the chick, day by 
 day, and had noted the appearance of its different organs 
 and envelopes. His masterly observations on the yolk-sac, 
 and its connection with the embryo, were claimed by the 
 evolutionists to be decisive as to the pre-existence of the 
 germ and its essential parts. " The membrane enclosing 
 the yolk," says Bonnet, " is continuous with the intestine 
 of the chick. The arteries and veins of the yolk are 
 branches of the mesenteric vessels of the foetus. The. 
 blood circulating in the ydlk-vessels receives its impulse 
 from the foetal heart. The yolk is, therefore, essentially a 
 part of the chick. But the yolk exists in the egg before 
 impregnation : consequently the chick also exists in the 
 egg before impregnation. . . . This proves incontestably 
 that the embryo is at first a part of the parent, and that its 
 existence is anterior to the time of conception." 
 
 Bonnet's assumption of the pre-existence of the embryo, 
 as well as of the germ, was not without a certain plausibility. 
 The organs of the embryo, when first formed, are, in fact, 
 not only small, but also colorless and transparent ; so that 
 they are seen with considerable difficulty, and may even be 
 overlooked for some time after they are really present. 
 Bonnet says this is the mistake made by the epigenesists. 
 " They estimate the time when the parts of an animal are 
 
 ' It is hardly necessary to say that this term, as used during the last century, had a 
 meaning different from that which attaches to it now. 
 
IN THE EIGHTEENTH CENTURY. 63 
 
 first created by that at which they firsi become visible ; and 
 whatever cannot be seen they assume has no existence." 
 But the organs in an imperfect embryo might very easily 
 have been there, though not sufficiently distinct to meet 
 the eye. "Do you wish," he says, "a short and ready 
 demonstration of this ? When the lung of an embryo chick 
 is first perceptible to the senses, it already measures ten 
 one-hundredths of an inch. It is evident that it would have 
 been visible when only half that size, were it not for the 
 extreme transparency of its tissue." 
 
 And so of all the other parts. Bonnet has more faith 
 than the epigenesists. He believes that the organs of the 
 embryo were there before he could see them, and that they 
 even existed from the beginning, though invisible, in the 
 unimpregnated egg. 
 
 But if the germ contains all the organs of the chick, 
 ready formed, only small and undeveloped, it contains 
 ovaries as well as the rest; and these ovaries contain 
 the germs of the next generation. , It is plain the series / 
 cannot end here. The germs of the second generation are' 
 chicks in miniature, as much as those of the first. Conse- * 
 quently they contain their own ovaries and germs, which, 
 in turn, contain others still ; and so on, without any defina- i 
 ble Hmit, one set of germs within the other in geometrical j 
 progression, each germ containing, not only its own embryo, i 
 but also all the embryos that can possibly be produced i 
 from it in unnumbered generations hereafter. 
 
 Bonnet does not shrink from the magnitude of this spec- 
 tacle. He rather glories in it, and enjoys the contemplation 
 of its unlimited perspective. " For my part," he says, " I 
 like to extend as far as possible the limits of creation. There 
 is a pleasure in the thought of this magnificent series of 
 organized beings, enclosed, like so many little worlds, one 
 
64 BUFFO N AND BONNET 
 
 within the Other. I see them receding by degrees, dimin- 
 ishing in regular order, and losing themselves at last in an 
 impenetrable night. It gives me a sense of satisfaction, 
 when I look at an acorn, to see in it the germ of a majestic 
 oak that, centuries hence, will shelter the birds and the 
 beasts under its branches ; or, still more, to behold in 
 Emilia's bosom the germ of the hero, who, thousands of 
 years hereafter, will found an empire ; or perhaps of the 
 philosopher who' shall discover to mankind the cause of 
 gravitation, the mystery of reproduction, or the mechanism 
 of our existence." ■ 
 
 This prospect, 'however, for the germs of the future, 
 which Bonnet found so attractive, was not as satisfactory 
 »to some of his contemporaries. They even haggled with 
 Jhim about the past. If the age of the world, as generally 
 ; admitted, was six thousand years, and if each generation 
 I of man is completed in thirty years' time, that would give 
 two hundred successive generations since Adam and Eye, 
 with about a thousand million human beings at present on 
 i^the earth. All these inconceivable numbers must have 
 been contained, under the form of germs, in the ovaries of 
 Eve. The minuteness of the embryos of the two-hundredth 
 generation, when enclosed in the body of our first parent, 
 was declared to be something incredible. Still more so 
 for plants which grow and fructify every year. Hartsoeker 
 calculated that the relation in size between the first wheat- 
 grain, and that to be produced at the end of six thousand 
 years, would be expressed by the figure of unity, followed 
 by thirty thousand zeros. 
 
 All this did not give Bonnet or his friends any discom- 
 fort. Such terrific estimates may serve to confound the 
 imagination ; but logic finds a sure refuge in the infinite or 
 
 ' (Euvres de Bonnet, torn. v. p. 206. 
 
IN THE EIGHTEENTH CENTURY. 65 
 
 indefinite divisibility of matter, Hartsoeker and his fol- 
 lowers, according to Bonnet, put the senses and the imagi- ' 
 nation in place of the understanding. They expect to see 
 and touch, so to speak, what can only be comprehended by 
 an effort of the mind. The hypothesis of the inclusion of 
 germs is above the level of such calculations, and is, he 
 concludes, a "splendid triumph of pure reason over the / 
 senses." 
 
 Bonnet's theory is by no means confined to the simple 
 hypothesis^ of one germ included within another. It is an 
 extensive and elaborate system, ramifying into all depart- 
 ments of natural history and physiology. The included 
 germs not only exist before fecundation, but they are nour- 
 ished and grow, in a way analogous to that of adult bodies. 
 There can be no doubt of this ; because the fowl's eggs cer- 
 tainly increase in volume before fecundation, and are to be j 
 seen in the ovary, of many different sizes and grades. But 
 the yolk is essentially a part of the chick: therefore, if 
 the yolk grows before fecundation, the embryo does the 
 same. Besides, in the theory of inclusion, the contained 
 germs diminish progressively, one within the other, t0"an 
 inconceivable minuteness. The outermost germ is, of , 
 course, the largest, and is nearly ready for impregnation./ 
 But when it has been fecundated, and has expanded into 
 the body of an adult female, the next included set of germs 
 have, in turn, come to be as large as the other was before ;; 
 and so on, in continuous order, the smaller germs gradually 
 moving up in the scale of magnitude, to be ready for im- 
 pregnation when their time arrives. The process of nutri- 
 tion and growth must therefore be going on in these 
 embryonic organisms, and has been going on in them ever 
 since the creation. 
 
 But how is the nutrition of the germs provided for, and 
 what are the materials used in their growth .' 
 
66 BUFFON AND BONNET 
 
 It is well known, says Bonnet, that the different parts of 
 the body are not nourished directly by the blood. A more 
 delicate and colorless fluid, called " lymph," sepa;rated from 
 the blood by appropriate organs, serves for the immediate 
 supply of the tissues. And as these tissues vary in fine- 
 ness and consistency, we can hardly doubt that the secre- 
 tory organs prepare for them different kinds of lymph, 
 more or less attenuated to correspond with their delicacy 
 of structure. Some tissues, as, for example, the brain and 
 nerves, must require a lymph many times finer and more 
 subtle than that employed for the grosser parts. 
 
 But the tissues of the included germs are finer still. If 
 we admit that there is no such thing as real generation, and 
 that every thing has been preformed frorrl the beginning, 
 then the germs which are to make their appearance a thou- 
 sand years hence have now actually within them,' and incal- 
 culably minute, all the parts characteristic of the species. 
 I Imagine the heart, the brain, the nerves, and the stomach 
 1 of such an embryo. Certainly, no lymph could penetrate 
 their tissues, or be of the least use for their nutrition. 
 What fluid is there in the body sufficiently attenuated and 
 ethereal to insinuate its particles into a structure of such 
 delicacy, and incorporate them with its substance ? There 
 is only one, and Bonnet secures it. This precious and 
 double-distilled material, which is alone capable of nourish- 
 i ing an unfecundated germ, is the nervous fluid. 
 
 The nervous fluid was not an invention of Bonnet's. It 
 was generally acknowledged, in his time, as the immediate 
 cause of nervous action. Like the electric fluid, it was 
 intangible and invisible, and was known only by its effects. 
 Its invisibility was due to its vaporous or aerial constitu- 
 tion ; and this enabled it to circulate in the delicate 
 passages of the nervous tissue, which were themselves 
 
IN THE EIGHTEENTH CENTURY. 67 
 
 invisible, owing to their minuteness. The nervous fluid, 
 or " animal spirits " so called, after being elaborated in the 
 brain, was disseminated through the nervous channels to 
 the various organs of sense and motion. Its existence was 
 proved by a very simple fact. If you tie a nerve going to 
 a muscle, the muscle is paralyzed. How could a ligature 
 cut off the nervous influence, except by arresting the pas- 
 sage of a fluid ? There was, therefore, little or no doubt in 
 regard to it. 
 
 The nervous fluid, in Bonnet's system, was not entirely 
 dissipated in the exercise of sensibility and motion. The 1 
 unconsumed portion, after returning to the brain, was again 
 sent out by similar channels to be used in nutrition. It 
 was carried by the maternal nerves to the ovaries, and there 
 distributed to the germs "of the first order," or those near- 
 est maturity.^ Elaborated anew, and still further spiritual- 
 ized by the organs of this delicate structure, it supplied a 
 finer nourishment to the germs of the second order: here 
 it underwent a similar preparation for those of the third 
 order ; and so on, to the belated and unfortunate germ 
 which "would not be^ready for fecundation till the end of' 
 the world." 
 
 This staggering array of infinitesimals, in structure and 
 function, only serves to increase the author's admiration, 
 and strengthen his confidence. " What an abyss of won- 
 ders," he says, " in the human brain ! Even a single fibre 
 of the brain is itself an abyss. What shall we say, then, if all 
 these mysteries, existing in the adult body, are repeated and 
 concentrated in so many organized atoms, enclosed one within 
 the other^ and growing constantly smaller in indefinite 
 progression .' " 
 
 The act of impregnation, in reproduction by sexes, comes 
 
 ' CEuvres de Bonnet, torn. x. p. 10. 
 
68 BUFFON AND BONNET 
 
 in for a very easy and natural explanation. The nervous 
 fluid is the appropriate nourishment for an unfecundated 
 germ. When this germ becomes a foetus it will be sup- 
 plied with lymph, and its organs will grow like those of the 
 adult. But how can it make the transition from one state 
 to the other, and how are the finely woven tissues of the 
 germ-embryo to be made capable of admitting the grosser 
 substance of the lymph } This is exactly the function of 
 the seminal fluid. It is not only a source of nourishment 
 for the mature germ, but it has a special stimulating influ- 
 ence on the embryonic heart. The pulsation of the heart 
 in the germ-embryo is very faint, and only serves for the 
 circulation of the nervous fluid. Consequently the unfe- 
 cundated germ increases but slowly, and never gets beyond 
 a certain stage of development. But when the seminal 
 fluid comes in contact with it, and penetrates its substance, 
 1 the heart's pulsation is increased in force. This causes an 
 "^expansion of the circulatory channels, an increased volume 
 of the circulating fluid, and consequently more rapid nour- 
 ishment ; and thus the limit is passed between the condi- 
 tion of the germ-embryo, whose tissues only admit nervous 
 fluid, and that of the growing foetus, that can thrive upon 
 the lymph. Once begun, the process naturally continues 
 until the body has attained its full development. 
 
 Still the theory of inclusion was not altogether free from 
 difficulty. One of its most troublesome problems .was 
 that of intestinal worms and other parasites. Bonnet 
 wrote a special treatise on the tcenia, partly devoted to dif- 
 ferent theories of its origin. He rejects, of course, the 
 idea of equivocal or spontaneous generation. But if, like 
 every thing else, it comes from pre-existing germs, are 
 these germs introduced into the intestine from without, or 
 did they exist beforehand in the embryonic human body 
 
IN THE EIGHTEENTH CENTURY. 69 
 
 itself ? If so, the germ of the first tape-worm, and, in fact, 
 of all which have existed since, must have been included in 
 the body of the first man. There are objections to be met 
 in either case, but the most singular are those connected 
 with the second. 
 
 In this view, the tasnia has a contemporaneous origin j 
 with man ; that is, it already existed in Adam, and so has j 
 passed into his posterity. But, according to Genesis, the 
 animals were all created before Adam : therefore the taenia ,| 
 must have first lived in a foreign element; but the fact is.U 
 we never find it except in the intestines. Besides, how' 
 can we suppose such a pest to have been placed in the! 
 body of our innocent progenitor, living in the earthly para-( 
 dise of the Garden of Eden } Valisnieri, who adopted the 
 contemporaneous theory, had an odd answer to this objec- 
 tion. He assumed, that, before Adam's fall, the intestinal 
 worms did not do him any harm, but, on the contrary, were 
 rather useful, in " consuming the superfluous humors and : 
 gently stimulating the intestinal walls." Bonnet thinks 
 this explanation a trifle far-fetched, and doubts whether 
 Adam, in his state of innocence, had any superfluous 
 humors, or needed any tape-worm to excite his intestines. 
 He prefers the idea of Leclerc, that the intestinal worms, 
 which are now so troublesome, only existed at first in/ 
 Adam under the form of eggs, and were not hatched until 
 after his disobedience." 
 
 But the line of descent for tape-worms is not yet quite 
 clear. Granting that they existed in Adam, either as eggs 1 
 or worms, how did they get into the body of Eve, through / 
 which they must have passed for transmission to posterity .M 
 The most direct route from the intestine, according to 
 Valisnieri, would be through the thoracic duct, which 
 
 ' CEuvres de Bonnet, torn. iii. p. 140. 
 
•JO BUFFON AND BONNET. 
 
 "mounts upwards along the ribs" to that which was taken 
 for the body of Eve. Bonnet is inclined to adopt a simpler 
 and less miraculous method of transfer, by supposing that 
 the eggs of the taenia are so small that they can pass through 
 the blood-vessels, and thus reach the vesiculse seminales. 
 " In this way," he says, with a puzzling kind of naivete, 
 "we can explain the whole thing without much difficulty, 
 znd without having recourse to divine power." 
 
 However, the author regarded the introduction of para- 
 sitic germs from without as, on the whole, the more prob- 
 able theory of their origin, especially as the weight of 
 evidence was already in that direction. 
 
 The system of Bonnet has applications to many different 
 points of general physiology ; such as the resemblance of 
 the young animal to both parentSy the production of hybrids 
 and monstrosities, and in particular to non-sexual genera- 
 tion, or multiplication by budding and division ; all of 
 which it explained with more or less ingenuity and success. 
 It had an apparent support in several recent and important 
 observations ; such as the existence in certain seeds of 
 an embryo plant, the multiplication by interior germs of 
 Volvox globator, the reproduction of aphides without im- 
 pregnation, and Haller's researches on the embryo chick, 
 Haller himself defended it from a variety of objections, 
 and adduced a number of arguments in its favor.' But 
 the theory itself went so far beyond the limits of possible 
 demonstration, that its basis of reality bore no calculable 
 proportion to its towering superstructure. It discounted 
 the results of embryological discovery at too exorbitant a 
 rate ; and it could not afford to have any of them turn out 
 differently from what was expected. This happened in the 
 case of the mammalian egg. Subsequent observations, made 
 
 ' Elementa Fhysiologiae Corporis Humani, 1766. Tom. viii. sect. ii. art. xxix. 
 
I2\r THE EIGHTEENTH CENTURY. 7 1 
 
 with better facilities, showed that the organs of the foetus 
 do not pre-exist in the ovum in the sense imagined by 
 Bonnet. The impregnated ovum has, it is true, a remark- 
 able property, by which each part subsequently assumes a 
 definite shape, and becomes a distinct organ. But the 
 actual configuration of these organs is certainly not present 
 in the ovum, because we can now see its original structure, 
 as well as the intermediate forms which afterward give 
 place to those of the embryo. The system of the inclu-' 
 sion of germs, in the time of its glory, embraced the whole 
 history of the world from beginning to end, and the mech-/ 
 anism of growth and -reproduction throughout organic na-^ 
 ture ; and enlisted in its behalf the discoveries of scientific j 
 research, as well as the results of logical deduction. But 
 it came to grief when the study of embryology had reached 
 a certain stage in its development, by demonstrating the 
 actual constitution of the mammalian egg. 
 
LECTURE III. 
 
 NERVOUS DEGENERATIONS AND THE THEORY OF SIR 
 CHARLES BELL. 
 
 Mr. President and Gentlemen, — It is now a little over 
 forty years since the beginning of an investigation which 
 has produced important changes in the study of the ner- 
 vous system. It relates to the alteration of structure 
 taking place in nerves after they have been divided by 
 transverse section. 
 
 The manner in which attention was first directed to this 
 point is as follows : It had long been known, that, when a 
 nerve was cut at any point, the immediate effect was a sus- 
 pension of its functional activity. If it were a motor nerve 
 which had been divided, voluntary motion was abolished 
 in the parts below ; and,-if a sensitive nerve, there was loss 
 of sensibility in the region where it was distributed. But 
 this interruption of nervous activity was not always perma- 
 nent. In some cases the power of motion or sensation 
 would return in the affected parts ; and the ends of the 
 nerve were then found to be re-united by cicatricial tissue, 
 in which there were connecting nerve-fibres of new forma- 
 tion. This re-union of a divided nerve, and the mode in 
 which its structure and functions were re-established, 
 formed the subject of much laborious investigation. 
 
 "^ ,, The observations in question were mainly directed to 
 72 
 
NERVOUS DEGENERATIONS, ETC. 73 
 
 the cicatrix between the ends of the divided nerve. This ! 
 was naturally supposed to contain the key of the whole 
 secret, and consequently received most of the attention 
 given to the subject. But in 1839 Nasse' extended his , 
 examination to the nerve-fibres at a lower level. He di- ' 
 vided the sciatic nerve in frogs and rabbits, and, after wait- 
 ing from two to five months, found that the fibres in the \ 
 separated portion of the nerve had become altered in struc- i 
 ture. They were of irregular form, granular, and semi- 1 
 opaque ; they often contained what seemed to be minute 
 fat-globules, from the degeneration of their myeline; and 
 they appeared to undergo, in this way, a gradual atrophy. 
 Nasse's observations were almost immediately followed by [ 
 those of Gunther and Schon,^ which were to the same - 
 effect. They were made on the divided sciatic nerve in 
 rabbits, from twelve hours to one year after the operation. ; 
 They showed that a nerve, after some days' separation from 
 its nervous centre, loses its irritability, so that its galvan- 
 ization will no longer produce contraction in the muscles 
 below, and that this loss of irritability coincides in time 
 with the granular degeneration of its fibres. 
 
 All these researches were connected with the question 
 of the re-establishment of the nervous continuity, and they, 
 did not extend for any great distance below the point of'| 
 section. Thus far, whenever observers use the term " re- ' 
 generation," as applied to divided nerves or nerve-fibres,( 
 they mean the formation of new connections in the cica- 
 tricial tissue. It was supposed, that, when this re-union 
 took place, the fibres below were restored to their normal 
 condition, the nerve being enabled, in this way, to resume 
 
 ■ Archiv fur Anatomie, Physiologie und wissenschaftliche Medicin. Berlin, 1839, 
 * Ibid., 1840, p. 270. 
 
74 NERVOUS DEGENERATIONS 
 
 its functions. The fact pf .degeneration was considered as 
 of secondary consequence, as limited in extent, and often of 
 temporary duration. 
 
 But ten years later the subject was taken up afresh by 
 Augustus Waller, and was treated by him in a manner so 
 original and so thorough, that it at once assumed a charac- 
 ter of the first importance. Waller began his professional 
 life in England as a practitioner of medicine ; but he had 
 a strong taste for independent research, and, after being 
 for a time professor of physiology in the medical school at 
 Birmingham, he transferred his residence to the Continent, 
 where he remained for most of his subsequent life, and 
 where the greater part of his scientific work was accom- 
 plished. For the anatomical study of muscular and ner- 
 vous fibres he employed the tongue of the living frog. This 
 gave him a great advantage; since the extensibility and 
 transparency of the organ enabled him to examine its in- 
 ternal parts in their normal place and condition, undis- 
 turbed by the contact of artificial reagents. He applied 
 this method to the observation of nerve-fibres, and the 
 change which they undergo after division; and thus fol- 
 lowed their granular degeneration in the living animal, from 
 day to day, under the microscope. 
 
 I One of his earliest and most important results was that 
 (the degeneration, in the fibres of a divided nerve below 
 I the point of section, extends through its whole length, 
 (reaching to its ultimate ramifications. After division of 
 ! the glosso-pharyngeal nerve in the upper part of the neck, 
 \ he saw its degenerated fibres in the tongue, and even in the 
 papillae of the mucous membrane. He also established 
 I the fact, that, in a nerve once divided, the degeneration of 
 jlthe affected fibres is final, and that, when the nervous 
 I functions are restored, it is by a process of regeneration ; 
 
AND THE THEORY OF SIR CHARLES BELL. 75 
 
 that is, the growth of new fibres throughout the separated/, 
 portion of the nerve. '< 
 
 But the principal merit in Waller's discovery was some- 
 thing additional. He did not rest content with its value as 
 an acquisition : he made it serve as an instrument. He 
 saw in the degeneration of divided nerve-fibres a means of 
 investigation, which he at once put to further use. A 
 nerve is often made up of fibres from different sources. It 
 receives branches of communication from other nerves; 
 and, in the inosculating filaments between them, there may 
 be fibres going or coming in either direction. In the ner- 
 vous trunks and branches these fibres are for the most part 
 hopelessly intermingled ; and it is impossible to follow them 
 for any distance by ordinary dissection. But by dividing, 
 in the living animal, a nervous trunk or branch near its 
 origin, Waller could afterward trace its degenerated fibres, 
 however erratic their course, or whatever their distribution. 
 He communicated his results to the French Academy of 
 Sciences,' under the title "A new Method for the Study 
 of the Nervous System, adapted for investigating the Ana- 
 tomical Distribution of the Nerves" 
 
 The first application of the new method was in the frog's 
 tongue. This organ is supplied by two nerves, correspond-\ 
 ing respectively to the glosso-pharyngeal and the hypo-) 
 glossal. After dividing one of these nerves, and allowing 
 time for its subsequent degeneration. Waller could deter- 
 mine the course and destination of all its fibres. ■ He fol- 
 lowed them throughout the frequent anastomoses of the 
 two nerves, where the altered fibres could always be distin- 
 guished from the normal ones around them ; and the two 
 kinds were so different in appearance, that, as he expressed j 
 it, " there could be no doubt whatever as to the origin of [ 
 either." 
 
 ' Cotnptes rendus de I'Acad^mie des Sciences. Paris, 1851 Tome xxxiii. p. 606. 
 
^6 NERVOUS DEGENERATIONS 
 
 These results were obtained by repeated and accurate 
 
 j experimental investigation ; and they have been fully cor- 
 
 iroborated by subsequent observers down to Vulpian,^ in 
 
 '1866, and Ranvier,^ in 1878. According to Vulpian, six 
 
 weeks after the division of the sciatic nerve in a dog, no 
 
 unaltered nerve-fibres could be found in the muscles of the 
 
 corresponding foot; and, in similar experiments by Ran-~ 
 
 vier on the rabbit, the terminal ramifications of the nerve 
 
 in the muscles of the leg contained only nerve-fibres with 
 
 disorganized and granular myeline. 
 
 The advantages in Waller's mode of procedure were so 
 obvious and so readily verified, that it was generally 
 adopted, and received the name of the " Wallerian method." 
 It at once yielded in the hands of its author much inter- 
 esting information. After division of the pneumogastric 
 nerve on one side, in cats, at the level of the larynx, granu- 
 lar degeneration was found throughout its peripheral fibres, 
 except in those joining it below from the inferior cervical 
 ganglion of the sympathetic, which remained normal. 
 Above this junction the nerve was wholly disorganized; 
 below, it contained a mixture of fibres, degenerated and 
 normal. It was thus made evident that the inosculating 
 I branches between the two nerves are given by the sympa- 
 thetic to the pneumogastric, and not by the pneumogastric 
 to the sympathetic. 
 
 Physiologists had often been at variance as to the origin 
 and character of the chorda tympani, — that remarkable 
 filament of communication between the facial and lingual 
 nerves. Was it a branch of the facial nerve going to the 
 lingual, or was it an offshoot from the lingual returning to 
 join the facial ? This point was determined by the method 
 
 ' Lejons sur la Physiologie du Systfeme Nerveux. Paris, i865, p. 243. 
 
 ' Legons sur I'Histologie du Syst^me Nerveux. Paris, 1878. Tome ii. p. 349. 
 
AND THE THEORY OF SIR CHARLES BELL. // 
 
 of section. Waller introduced his stilet into the middle 
 ear, and divided the filament where it crosses the membrana 
 tympani. Fifteen or twenty days afterward, nearly all its 
 fibres were degenerated between the point of section and 
 the lingual nerve ; that is, in the direction of their periphe- 
 ral distribution. The chorda tympani was consequently 
 shown to be a branch of communication from the facial 
 nerve to the lingual. 
 
 In this way many doubtful questions of nervous distri- , 
 bution received their solution. The granular degeneration 
 of the divided nerve-fibres became an artificial aid to the 
 anatomist, of the same value as the injection of minute 
 blood-vessels with opaque pigment. Even a single dis- 
 organized fibre could be distinguished among a crowd of 
 normal ones ; and, in a mixture of the two, their numerical 
 proportion could be fairly determined. 
 
 But Waller did not remain satisfied with this success. \ 
 He determined to apply the same method to the study of 
 the nerve-roots ; • and in doing so he opened a new chap- 
 ter of nervous physiology, and greatly enlarged the field of 
 his operations. 
 
 The history of these experiments is so well known, that 
 they only need to be stated in a few words. Waller had 
 already shown, that, if a spinal nerve be divided at its i 
 exit from the vertebral canal, all its peripheral parts suffer \ 
 degeneration. Motor and sensitive fibres are alike involved,!^ 
 and can be traced, in their disorganized condition, to their 
 ultimate termination in the muscles and the integument.1 
 On continuing the same mode of investigation within the , 
 vertebral canal, if the anterior root only were divided, the j 
 
 • His second communication to the French Academy was entitled "Experimental 
 Researches on the structure and functions of the ganglia." Comptes rendus de 
 I'Acad^mie des Sciences. Paris, 1852. Tome xxxiv. p. 524. 
 
78 NERVOUS DEGENERATIONS 
 
 ! motor fibres alone degenerated in the trunk and branches 
 
 ' of the nerve, while its sensitive fibres remained normal ; 
 if the posterior root were divided outside its ganglion, the 
 
 \sensitive fibres of the nerve degenerated, and the motor 
 fibres were unaffected ; and in both cases the portion of 
 [the nerve-root still connected with the spinal cord pre- 
 'served its normal structure. But, if the posterior root were 
 
 , divided above the situation of its ganglion, two remarkable 
 consequences followed, — first, there was no degeneration 
 of the nerve outside the ganglion ; and, secondly, that por- 
 tion of the nerve-root separated from the ganglion, but still 
 
 I united with the spinal cord, suffered complete degeneration. 
 These effects were repeatedly observed, under varied 
 conditions, until there was no doubt in regard to them. 
 In the frog, when both roots of a sciatic nerve were divid- 
 ed above the level of the ganglion, there was, of course, 
 complete loss of both motion and sensibility in the para- 
 lyzed limb ; but, while all its muscular nerve-fibres degen^ 
 crated, the sensitive fibres distributed to the skin exhibited 
 no alteration, even at the end of two months. Similar 
 experiments on warm-blooded animals turned out in the 
 same way. In dogs and cats. Waller utilized for this pur- 
 pose the exceptional position of the second cervical nerve, 
 the _:two_roots_of^ which remain distinct iirTEese''anirnals 
 until after thei r emerge nce from thelriterYertebral foram- 
 ina. He could thus operate on the nerve-roots without 
 opening the vertebral canal ; and by this means Ae verified 
 Magendie's discovery, that section of the anterior root 
 destroys the power of motion, and that of the posterior 
 root the power of sensibility. But he demonstrated, fur- 
 thermore, that, when both roots are severed above the level 
 of the ganglion, all the motor fibres of the nerve degener- 
 ate, and all its sensitive fibres remain sound. 
 
AND THE THEORY OF SIR CHARLES BELL. 79 
 
 It is therefore evident that the immediate loss of action 
 in a divided nerve, and its structural degeneration, are two 
 independent phenomena, having nothing to do with each 
 other. A motor nerve, when cut, ceases to excite volun- 
 tary motion, not because its fibres are incapacitated by 
 degeneration, but because their physical continuity is bro- 
 ken at one point ; and a sensitive nerve, under like condi- 
 tions, can no longer communicate with the sensorium, for 
 the same reason. The proof of this is, that, if we galvanize 
 the motor nerve below the point of section, it at once calls 
 out the action of its muscles ; and a like stimulus, applied 
 to the sensitive nerve above its point of section, will be 
 transmitted to the brain, and produce the effect of a sen- 
 sation. This is the state of things immediately after the 
 nerve has been cut. 
 
 But at the end of some days a different condition shows 
 itself in the peripheral part of the divided nerve. Its 
 fibres then become unable to re-act under artificial stimulus, 
 and their galvanization no longer produces muscular con- 
 traction. This is due to their progressive degeneration, 
 which requires time for its development, but which, at a 
 certain stage, destroys the functional activity of the nerve- 
 fibres. Simple paralysis of motion and sensation is con- 
 sequently the immediate result of division of a spinal nerve. 
 Its degeneration, with loss of irritability, is a subsequent 
 result. The independence of the two is especially mani- 
 fest in Waller's experiments on the spinal 'nerve roots. 
 When both are divided above the level of the ganglion, the 
 motor fibres of the anterior root become degenerated 
 throughout their distribution in the paralyzed parts ; but 
 the sensitive fibres from the posterior root remain every- 
 where sound in the integument of the same region. ' 
 
 From these facts Waller concluded that the two sets of 
 
80 NERVOUS DEGENERATIONS 
 
 ' nerve-fibres had different centres of nutrition ; that the 
 motor fibres of the anterior root were dependent, for struc- 
 tural integrity, on their connection with the spinal cord, 
 while the sensitive fibres of the posterior root depended on 
 their connection with the spinal ganglion. He was fully 
 justified in claiming that his results were unequivocal, and 
 " calculated to throw a new light on the relations of the 
 nervous system." 
 
 For Waller's communications on this subject to the 
 French Academy, he was awarded, in 1856, the Montyon 
 Prize of Experimental Physiology, by a committee consist- 
 ing of Flourens, Rayer, Serres, Milne-Edwards, and Ber- 
 nard. In reporting the decision of the committee, the 
 Achairman, Bernard, begins with the following words : " The 
 /discoveries usually presented to us are of two different 
 Ikinds. In some, the facts have been already, to a certain 
 [extent, anticipated, and are mainly serviceable in their new 
 iform by increasing the precision of our knowledge, and by 
 /elucidating subjects previously obscure. Those of the 
 / other kind, on the contrary, are unexpected. The principal 
 feature in them is their novelty; and they enlarge the 
 boundaries of science, not merely by the solution of par- 
 ticular questions, but still more by the ideas and sugges- 
 tions which they originate. It is to the last of these two 
 I categories that the present essay belongs." 
 
 It soon appeared that the committee were not mistaken 
 in their estimate. The immediate result of Waller's re- 
 I searches was the discovery of the so-called " centres of 
 ^ nutrition " for nerve-fibres of different kinds. The exist- 
 ence of these centres of nutrition was fully demonstrated ; 
 although it was not quite plain, and has not even yet be- 
 come so, in what way their influence is exerted. But there 
 was also the additional discovery that the degeneration of 
 
AND THE THEORY OF SIR CHARLES BELL. 8 1 
 
 divided nerve-fibres may take place in opposite directions. 
 It may be centrifugal, that is, from the point of section to 
 the periphery ; or it may be centripetal, that is, from the 
 point of section toward the spinal cord and brain. This 
 fact afterward became the most prolific source of further/ 
 investigation. 
 
 Up to this point Waller's experiments had been confined \ 
 to the spinal nerves and nerve-roots. In his last communi- 
 cation to the French Academy, ' he goes a step farther, 
 and traces the course of similar degenerations in the cord 
 itself. He divided the spinal cord, in a dog, between the^ 
 third and fourth lumbar vertebras. After twenty days the] 
 cord was found to be re-united at the line of section. But • 
 above the section the posterior columns were disorganized! 
 for the space of about two vertebrae ; while in the inferior 
 segment the same columns, as well as the posterior nerve- 
 roots, were normal. The anterior nerve-roots, on the con- / 
 trary, were degenerated for the first three pairs below the ,' 
 section; and the same alteration continued, diminishing 
 gradually in amount, for the fourth, fifth, and sixth pairs. 
 Thus there may be, within the columns of the cord, as well \ 
 as in its nerve-roots, centripetal or centrifugal degeriera-j 
 tions, affecting exclusively particular nervous tracts. 
 
 This discovery corresponded with certain pathological 
 observations in man, made about the same time by Tiirck, 
 and communicated by him to the Academy of Sciences at 
 Vienna.^ They were cases in which post-mortem examina- 
 tion revealed an old morbid deposit in the brain, together 
 with structural alteration of the spinal cord on the opposite 
 side. This alteration consisted mainly in a production of 
 
 • Comptes rendus de 1' Academic des Sciences Paris, 1852. Tome xxxv. p. 301. 
 = Sitzungs-berichte der kaiserlichen Akademie der Wissenschaften. Wien, 1851, 
 p. 288. 
 
82 NERVOUS DEGENERATIONS 
 
 abnormal granular cells, occupying the tissues of the cord, 
 and resembling those met with about the morbid deposit in 
 the brain. The most striking feature of the alterations in 
 question was that they occupied definite longitudinal tracts, 
 the rest of the cord being normal. By examining succes- 
 sive sections at different levels, it became evident, that, 
 from the lesion in the brain to the lower end of the spinal 
 cord, only certain bundles of fibres were affected ; and 
 these bundles corresponded in situation with those which 
 could be demonstrated by dissection in normal specimens 
 of the cord, after hardening in alcohol. 
 
 Observing this correspondence, in certain cases, between 
 the degenerated tracts and parts already known, the author 
 was led to apply the same means of observation to the 
 study of anatomical relations not so well understood. The 
 attempt proved successful. The first fact which it brought 
 out was a distinction between the anterior and posterior 
 segments of the lateral column. No such distinction can 
 be shown by ordinary dissection ; most of the nerve-fibres 
 in both segments running in a direction parallel with each 
 other, and between origins and terminations too distant to 
 be traced. But, in some of the cases mentioned, the mor- 
 bid alteration of the lateral column was found only in its 
 posterior part, the anterior part remaining sound ; and this 
 difference was so constant, in sections made at various 
 levels, as to leave no doubt that there must be some ana- 
 tomical distinction between the two segments of the column, 
 extending through the greater part of its length. 
 
 It was also seen, in these cases, that, on approaching the 
 upper end of the cord, the degenerated tract shifted its 
 position forward and inward, and, at the medulla oblongata, 
 crossed into the anterior pyramid of the opposite side. 
 Thence it extended upward through the pons Varolii, where 
 
AND THE THEORY OF SIR CHARLES BELL. 83 
 
 the distinction was extremely evident, the transverse bundles 
 of the pons being free from alteration, while its longitudinal 
 bundles were deeply affected. It appeared, therefore, that 
 the degenerated tracts had been invaded by a special altera- 
 tion confined to their own limits, and extending continu- 
 ously from the seat of the brain-lesion, through the crus 
 cerebri, the pons, and the anterior pyramid of the same side, 
 and thence, through the posterior part of the lateral column 
 on the opposite side, to the lower end of the spinal cord. 
 
 This showed that there was a longitudinal tract of nerve- 
 fibres, reaching for long distances in the cerebro-spinal 
 axis, and having, so to speak, its own centre of nutrition ; 
 and that, when this centre of nutrition was disturbed or 
 disorganized by local lesion, the subsequent degeneration 
 might extend throughout the tract in question, while others 
 in its immediate contiguity remained sound. The cases 
 observed by Tiirck were accompanied by more or less 
 hemiplegia; and while the brain-lesion, as well as the de- 
 generation of the pons and anterior pyramid, were, as usual, 
 on the opposite side, that in the spinal cord was on the 
 same side with the paralysis. Every thing showed the de- 
 generated portions in the spinal cord to be continuous with 
 the opposite anterior pyramids and their extension in the 
 crura cerebri, and consequently to represent the motor 
 tracts of the cerebro-spinal axis. But while Tiirck followed 
 the crossing of these tracts at the decussation of the pyra- ; 
 raids, he also showed that in certain cases their crossing 
 was incomplete ; that is, although the bulk of a degener- 
 -ated anterior pyramid crosses at the level of the decussa- 
 tion, and re-appears in the lateral column of the opposite 
 side, a remnant of its fibres continue their downward course 
 for some distance on the same side. These direct columns, 
 visible more or less constantly in the cervical portion of 
 
84 NERVOUS DEGENERATIONS 
 
 the cord, are still known by the name of the " columns of 
 Turck." 
 
 But his most important results were those indicating the 
 difference, in anatomical connection, between the anterior 
 and posterior parts of the lateral column. These two parts 
 were distinguishable from each other by the granular 
 deposit with which one was infiltrated, while the other 
 remained normal ; and the deposit appeared with such 
 regularity at the same spot in successive sections, and 
 crossed so distinctly at the decussation of the pyramids, as 
 to show that it followed the course of an associated bundle 
 of nerve-fibres. As this bundle represented, in the cord, 
 the continuation of the anterior pyramid above, the whole 
 tract, from end to end, afterward receiyed the name of the 
 "pyramidal tract." The first indication of the exact 
 locality of this tract in the lateral columns was derived from 
 the sections of Tiirck. 
 
 The same author made an incidental observation, a,fter- 
 ■ ward seen to be very important, in regard to degenerations 
 from local lesion of the cord itself. They were instances 
 of paraplegia from compression or disorganization of the 
 spinal cord at one point. In these cases the portion of 
 the cord above the lesion, while mainly free from degen- 
 eration, nevertheless contained single degenerated tracts, 
 always identical in situation, extending upward to the 
 medulla and pons. But these tracts were not the same 
 with those found degenerated after a brain-lesion ; and the 
 latter were entirely sound in the above-mentioned cases 
 of injury to the cord. If one portion of the spinal cord, 
 therefore, can degenerate in consequence of a lesion situ- 
 ated above it, another, and an entirely different portion, 
 may be affected by degenerations coming from below. 
 
 So far, the knowledge of degenerations within the spinal 
 
AND THE THEORY OF SIR CHARLES BELL. 85 
 
 cord had been mainly acquired from pathological obser- 
 vations in man. But, about ten years ago, Goltz, in Stras- 
 burg, undertook a series of investigations on the functions 
 of the lumbar portion of the spinal cord, with regard to its 
 influence on the sexual and urinary organs. His experi- 
 ments were performed on young dogs, by dividing the cord 
 transversely at the lower end of the dorsal region, and then 
 preserving the animals long enough to study the permanent 
 effects of the operation. By gradual improvements in the 
 selection of animals, the operative procedure, and the sub- 
 sequent treatment, he became very successful. The cord 
 was divided without serious injury to the vertebral column 
 or the external parts. Dogs of the proper age and organi- 
 zation were not dangerously affected by the operation, 
 sometimes taking food within the first twenty-four hours, 
 and generally regaining their appetite in a few days. The 
 wounds healed in two or three weeks ; and some of the 
 animals were preserved several months, remaining para- 
 plegic, but otherwise in good condition. 
 
 This offered a valuable material for the study of degenera- 
 tions in the spinal cord, and it was utilized for that purpose 
 by Schieferdecker,' the assistant of Goltz, who was familiar 
 with the history and condition of the animals employed. 
 
 On examining microscopic sections of the cord, in these 
 cases, the granular degeneration of the pyramidal tracts 
 was recognized. It was present in every instance, and had 
 invariably taken a descending course from the point of 
 section to the lower extremity of the cord. This portion 
 of the spinal cord, therefore, had become altered in the same 
 way as a divided spinal nerve, that is, from the centre 
 toward the periphery ; and the degeneration of the pyram- 
 
 ' Archiv fiir pathologische Anatomie imd Physiologie. Berlin, 1876. Band Ixvii. 
 p. 542. 
 
86 NERVOUS DEGENERATIONS 
 
 idal tract, whether it be due to a cerebral lesion, or to 
 compression or section of the cord itself, follows the same 
 direction. 
 
 . On the other hand, when a similar degeneration takes 
 'place in the posterior columns of the cord, it is always 
 ascending. We have now the experience of Charcot ' to 
 corroborate the earlier assertion of Tiirck, that such 
 posterior degenerations invariably extend from the point 
 of injury or disease upward toward the brain, and never in 
 a downward direction. By this means the ascending and 
 descending degenerations of the spinal cord were established 
 with the same certainty as the centripetal and centrifugal 
 degenerations of the nerve-roots, and, like them, were 
 shown to occupy separate tracts, easily distinguishable 
 from each other. 
 
 These facts greatly increased the confidence of physi- 
 ologists in the value of degenerations, as indicating the 
 continuity and destination of nerve-fibres. It was evident 
 from the first that a divided nerve-fibre degenerates because 
 of its severance from some special nerve-centre, and, once 
 cut off from this centre, it becomes affected throughout 
 its length. When we see, in the spinal nerves, complete 
 degenerations strictly limited to the ramifications of a 
 single trunk, and similar alterations in the spinal cord 
 equally confined to particular tracts, we can hardly refuse 
 the conviction that these tracts also consist of continu- 
 ous nerve-fibres following a common direction. Waller's 
 experiments on the nerve-roots show, that, when such a 
 group of fibres meets a ganglion or centre of gray sub- 
 stance interposed in its course, the degeneration does not 
 pass this point. Either the injured fibres receive an 
 
 ' Legons sur les Localisations dans les maladies du Cerveau et de la Moelle 6pinifere. 
 Paris, 1880, p. 247. 
 
AND THE THEORY OF SIR CHARLES BELL. 87 
 
 accession of nutritive energy from the ganglion, or else 
 they terminate in its substance and are replaced by new 
 fibres originating from its gray matter. This gives a 
 special significance to the fact observed by Charcot' in 
 regard to disease of the pyramidal tracts. These tracts are 
 manifestly the channels for voluntary motion in the spinal 
 cord. The paralysis caused by either their morbid altera- 
 tion or their experimental division shows that they are the 
 paths followed by voluntary motor impulses from the brain 
 to the anterior nerve-roots. But descending degenerations 
 of the pyramidal tract, however complete in the spinal 
 cord, do not usually extend to the motor nerves or nerve- 
 roots. This is easily explained on the assumption that the 
 fibres of the pyramidal tract terminate in the gray sub- 
 stance of the anterior horn, while those of the anterior 
 root have their origin at the same point. The nerve-root 
 therefore degenerates only when divided beyond its emer- 
 gence from the anterior horn. 
 
 Further study of the posterior columns led to the dis- 
 covery of two different kinds of degeneration, as well as 
 to a distinction between different parts of these columns. 
 Hitherto the morbid alteration of nervous tracts had ap- 
 peared only as the consequence of a local lesion in either 
 the nerves, spinal cord, or brain ; and it extended upward 
 or downward from its point of origin, as if propagated in 
 certain directions along the natural route of the nerve-fibres. 
 These alterations of structure Were therefore known as 
 "secondary degenerations," because resulting from some 
 primary affection in a different locality. But it appeared 
 that certain tracts in the spinal cord might also be the seat 
 of primary degenerations, originating within their own sub- 
 stance independently of lesions elsewhere. As these alter- 
 
 • Lejons sur les maladies du SysWme Nerveux. Paris, 1877. Tome ii. p. 219. 
 
\of 
 
 88 NERVOUS DEGENERATIONS 
 
 ations often followed a similar course to those of secondary 
 origin, occupying only their own tracts or systems of 
 fibres, they received the name of " systematic degener- 
 ations." 
 
 The posterior columns of the cord were liable to both 
 secondary and systematic degenerations. But these two, 
 affections occupied different regions, thus showing an 
 anatomical distinction, in the posterior column, like that 
 already established between the front and back parts of the 
 lateral column. 
 
 In the posterior column of the cord, the inner part, next 
 the median line, is a narrow band, visibly marked off from the 
 remainder in the cervical region by a slight furrow on 
 the surface. This is t\i& funiculis gracilis, or the "column 
 
 Goll." At the medulla oblongata it diverges from the 
 median line obliquely upward, forming, on the inner border 
 of the restiform bodies, the so-called " posterior pyramids." 
 The columns of Goll are the seat of the ascending degener- 
 ations noticed by Tiirck. When they are affected in this 
 way, their alteration extends unbroken from its starting- 
 point often quite to the level of the medulla oblongata, 
 whence it is inferred that they are composed throughout of 
 continuous fibres. 
 
 But the remainder of the posterior cblumn is affected by 
 degenerations which have a different form and different 
 results. This portion is included between the column of 
 Goll and the posterior nerve-roots, and forms the outer 
 part of the posterior column. It has not received a dis- 
 tinct name, but is important, owing to its connection with 
 locomotor ataxia. It is regarded as made up of compara- 
 tively short fibres, originating and terminating in succes- 
 sion along the cord, for the reason that its secondary 
 degenerations are never propagated to any considerable 
 
AND THE THEORY OF SIR CHARLES BELL. 89 
 
 distance, extending at most only two or three centimetres 
 above their origin.' But it is liable to systematic altera- 
 tions, mainly sclerosis, invading a large portion of its extent ; 
 and, when such alterations occur, they are accompanied by 
 symptoms of locomotor ataxia, never produced by struc- 
 tural disease in other parts. According to the observa- 
 tions of Charcot,! the columns of GoU may be completely 
 degenerated without causing any signs of ataxia, while 
 sclerosis of the outer part of the posterior columns is al- 
 ways accompanied by ataxic symptoms ; and these symp- 
 toms are in proportion to the extent of the degeneration. 
 
 Lastly, the anatomical study of nervous tracts, by the aid 
 of secondary degenerations, has been carried into the 
 brain itself. There is already a reasonable certainty of 
 the extension of the pyramidal tracts through the anterior 
 pyramids, the pons Varolii, and the crura cerebri ; and the 
 fibres of the crus cerebri are manifestly succeeded by the 
 diverging expansions of the internal capsule and the corona 
 radiata. These expansions are, beyond question, for the 
 most part, means of communication between the cerebral 
 convolutions and the ganglia at the base of the brain, while 
 the fibres of the crus cerebri connect the ganglia with the 
 spinal cord below. But, beside these interrupted communi- 
 cations, are there also direct fibres, running continuously 
 from the motor centres in the cerebral cortex, through the 
 corona radiata and internal capsule, into the pyramidal 
 tract .' The centres of motion about the fissure of Rolando 
 might produce muscular contractions, when galvanized, 
 either through the intervention of the cerebral ganglia, or, 
 more directly, by means of continuous fibres. Such direct 
 
 ' Legons sur les maladies du Systfeme Nerveux. Paris, 1877. Tome ii. p. 11. 
 Legons sur les Localisations dans les maladies du Cerveau et de 3a Moelle ^pinifere. 
 Paris, 1880, p. 259. 
 
90 NERVOUS DEGENERATIONS ^ 
 
 tracts have been sometimes imperfectly recognized in the 
 examination of hardened specimens ; but they have never 
 been clearly demonstrated by this method, owing to the 
 complicated interlacement of fibres in the upper part of the 
 internal capsule. Their existence is mainly inferred from 
 the course of descending degenerations in this region. Ac- 
 cording to Charcot, destructive lesions of the cortex, in the 
 anterior and posterior central convolutions, give rise to de- 
 generations in the white substance, which pass downward 
 through the internal capsule, crura cerebri, anterior pyra- 
 mids, and lateral columns of the cord. These degenera- 
 tions may exist without lesion of the cerebral ganglia ; and 
 they are not produced by morbid alterations in other parts 
 of the brain than those about the fissure of Rolando. Sim- 
 ilar observations, during a period of fifteen years, point 
 with much significance to a continuity of fibrous structure 
 throughout this tract. If we remember the uniform prog- 
 ress of discovery thus far made by these investigations, — 
 first in the nerves, then in the nerve-roots, then in the 
 columns of the spinal cord and medulla oblongata, — it does, 
 not seem presumptuous to expect, from their further prose- 
 cution, a corresponding success in the more difficult explo- 
 ration of the brain. 
 
 The study of nervous degenerations has already borne 
 fruit of great value. Like many other researches of simi- 
 lar character, it was at first a matter of purely scientific in- 
 terest, without any apparent bearing on the treatment or 
 even the pathology of disease. But it has grown in impor- 
 tance with every additional observation, and it is now an 
 indispensable aid in investigating the morbid affections of 
 the nervous system. It has extended our anatomical 
 knowledge far beyond its previous limits. It has demon- 
 strated the existence of nervous connections which could 
 
ANV THE THEORY OF SIR CHARLES BELL. 91 
 
 hardly have been detected in any other way. It has shown 
 the relation between certain forms of paralysis and the 
 altered structure of particular nervous tracts, and it seems 
 likely to yield results of still wider application before its 
 capacity is exhausted. It began with the degenerating 
 fibres of a divided sciatic nerve, and it has now reached the 
 intricate region of the white substance of the cerebral 
 hemispheres. 
 
 Sir Charles Bell's theory of the nervous system- is 
 of so recent a date, comparatively speaking, that its traces 
 have not entirely disappeared from our nomenclature. The 
 student will still find, among the synonymes in some ana- 
 tomical text-books, such names as the " Respiratory nerve 
 of the face," or the " Superior and External respiratory 
 nerves of Bell." But the system of which these names 
 formed a part has become so obsolete, that their signifi- 
 cance is hardly remembered; and even the distinctive 
 features of the theory itself have been forgotten in the 
 discussion of more important topics connected with the 
 nervous system. 
 
 Among the eminent medical men of the present century, 
 perhaps none have attracted more cordial admiration than 
 Sir Charles Bell. His earnest and strictly professional 
 ambition, his restless mental activity, his versatility of 
 talent, and his genial and enthusiastic disposition, secured 
 him a rapid success and a position of acknowledged superi- 
 ority. " Anatomist, surgeon, author, artist, and critic," he 
 taught anatomy by lectures and demonstrations, was the 
 equal of Cooper and Cline in practical surgery, published 
 his magnificent works on the " Operations of Surgery " and 
 the "Anatomy of Expression," illustrated by himself, and 
 created the reputation of the Middlesex Hospital as a cen- 
 
92 NERVOUS DEGENERATIONS 
 
 tre of medical instruction. When he received the order of 
 knighthood, in 183 1, at the same time with Herschel, Bab- 
 bage, and Brewster, he thought more of his companions 
 than of his title. " The batch," he said, " makes it respect- 
 able." He always retained a strong attachment to his 
 early friends and family relatives, and to the pleasures and 
 sports of a country life ; and, if he experienced some dis- 
 appointment as to the success of his scientific opinions, 
 this was fully compensated by his general popularity and 
 his high professional reputation. 
 
 Bell's attention was especially attracted to the nervous 
 system in 1807, a few years after his arrival in London, 
 and while occupied as lecturer in a private medical school 
 established by himself. In his demonstrations he was 
 struck with the apparent complexity of the nervous appara- 
 tus, and the difficulty of presenting it fairly to the compre- 
 hension of his audience. His mind dwelt persistently on 
 this subject, with a view of reaching some more intelligible 
 arrangement of what seemed so confused and discon- 
 nected. His thoughts were first turned to the anatomy of 
 the brain, which, he says, at that time " occupied his head 
 almost entirely." ' He puzzled over the varied form and 
 structure of the cerebrum and cerebellum, the processes, 
 protuberances, and ganglia at the base of the brain, and 
 the connections and course of the cranial nerves. He 
 tried to reduce these complicated parts to something like 
 order in his mind, and to divine the secret of their anatomi- 
 cal relations. 
 
 This was the origin of his new system in cerebral anat- 
 omy; and, when once it had assumed a distinct form, it 
 grew in importance, and took entire possession of his con- 
 
 ' Letters of Sir Charles Bell. Selected from his correspondence with his brother, 
 George Joseph Bell. London, 1870, p. 117. 
 
AND THE THEORY OF SIR CHARLES BELL. 93 
 
 viction and imagination. He made it the subject of his 
 lectures, and speaks of it in his correspondence with the 
 greatest enthusiasm. " I hinted to you," he says in a let- 
 ter to his brother in Edinburgh, " that I was burning, or on 
 the eve of a grand discovery. ... I really think this new 
 anatomy of the brain will strike more than the discovery 
 of the lymphatics being absorbents. . . . My object is to 
 lecture it, to make the town ring with it, as it is the only 
 new thing that has appeared in anatomy since the days of 
 Hunter, and, if I make it out, as interesting as the circula- 
 tion or the doctrine of absorption." • 
 
 Up to this time there is no trace of any experimental 
 investigations by Bell in regard to the subject. His system 
 was wholly inferential, based on the facts of anatomical 
 structure. But a year or two later he felt the necessity of 
 making some experiments, especially as he had formed the 
 intention of printing his views in a pamphlet for private 
 distribution. He hoped by this means to elicit the opinion 
 of the representative men of the profession, and to see 
 whether his innovations would be likely to meet with ap- 
 proval. 
 
 Accordingly, in iSio,^ he records having made two ex- 
 periments with a satisfactory result ; so much so, that he 
 believes he is now about to establish his system on facts, — 
 " the most important that have been discovered in the his- 
 tory of the science." And in 181 1 his essay was printed, 
 under the title " Idea of a New Anatomy of the Brain ; 
 submitted for the Observations of his Friends, by Charles 
 Bell, F.R.S.E."3 
 
 The idea developed in this essay, and the importance 
 
 ' Letters of Sir Charles Bell, pp. 117, 118. '■ Ibid., p. 170. 
 3 Reprinted in the Journal of Anatomy and Physiology. Cambridge and London, 
 1869. Vol. iii. p. 153. 
 
94 NERVOUS DEGENERATIONS 
 
 attached to it in the mind of its author, can be best under- 
 stood from Bell's own account of its origin and growth. 
 In a letter to his brother a year before, he details his plan 
 of investigation, and the object to be accomplished. He 
 had already reached the conviction, on anatomical grounds, 
 that the several divisions of the encephalon were different 
 from each other in function, and especially that a wide 
 distinction of this kind existed between the cerebrum and 
 the cerebellum. But bow gain access to these deep-seated 
 and vascular parts, so as to experiment upon them ? This 
 seemed too diiificult an undertaking. It might be possible, 
 however, to expose, for that purpose, the spinal cord and 
 its nerve-roots ; and this is what he accordingly did. " It 
 occurred to me," he says, " that, as there were four grand 
 divisions of the brain, so were there four grand divisions 
 
 ^ of the spinal marrow : first, a lateral division, then a divis- 
 ion into the back and fore part. Next it occurred to me 
 that all the spinal- nerves had, within the sheath of the 
 spinal marrow, two roots, — one from the back part, another 
 from before. Whenever this occurred to ine, I thought 
 that I had obtained a method of inquiry into the functions 
 of the parts of the brain." ' 
 
 That is to say, experiments on the anterior columns of 
 the spinal cord, or the anterior nerve-roots, would throw 
 light on the functions of the cerebrum, with which they 
 were anatomically connected. Experiments on the poste- 
 rior columns of the cord, or the posterior nerve-roots, 
 
 I would indicate the function of the cerebellum, to which, 
 
 I he thought, these parts belonged. 
 
 These are the experiments described in the " Idea of a 
 New Anatomy of the Brain," and this is the meaning 
 attributed to them by its author. He found that irritation 
 
 • Letters of Sir Charles Bell, p. 170. 
 
AND THE THEORY OF SIR CHARLES SELL. 95 
 
 applied to the anterior part of the spinal cord produced 
 contraction in the voluntary muscles, while a similar injury 
 inflicted on its posterior part did not do so. On laying 
 bare the roots of the spinal nerves, he could cut across the 
 posterior fasciculus without convulsing the muscles; but 
 touching the anterior fasciculus at once produced convul- 
 sions. " Such were my reasons," he says, "for concluding 
 that the cerebrum and cerebellum were parts distinct in 
 function, and that every nerve possessing a double function 
 obtained that by having a double root." ' 
 
 The distinction made by Bell between the two divisions 
 of the encephalon is this : the cerebrum is the organ of the [ 
 mind, of conscious sensation and volition: consequently,! 
 the anterior roots of the spinal nerves, being connected with 
 the cerebrum through the anterior part of the spinal cord,^ 
 are subservient to sensation and volition, and, when arti- 
 ficially irritated, cause contraction in the voluntary muscles. ' 
 The cerebellum, on the other hand, presides over the secret 
 or unconscious operations of the bodily frame, as in the 
 vital action of the internal organs : consequently, irritatioi|'^ 
 of the posterior columns of the cord, or the posterior nervd- 
 roots, has no perceptible effect on the voluntary muscles, 
 A spinal nerve accordingly possesses two roots, because it 
 performs two sets of functions, — one, those of consciousness 
 and volition, derived from the cerebrum ; the other, those 
 of unconscious vital influences, derived from the cerebellum. 
 The cranial nerves, however, have for the most part only a 
 single root, and exercise but one set of functions, corre- 
 sponding to their place of origin. Thus " the eighth nerve 
 (par vagum) is from the (back) portion of the medulla ob- 
 longata which belongs to the cerebellum ; the ninth nerve 
 (sublingual) comes from the (front) portion which belongs 
 
 ' Reprint in the Journal of Anatomy and Physiology, vol. iii.p. 161 
 
96 NERVOUS DEGENERATIONS 
 
 to the cerebrum. The first is a nerve of the claSs called 
 vital nerves, controlling secretly the operations of the body ; 
 the last is the -motor nerve of the tongue, and is an instru- 
 ment of volition." ' This is the substance of the views 
 contained in the essay of 1811. 
 
 Bell was much disappointed in the impression produced 
 by this pamphlet. It turned out an " unpropitious experi- 
 ment ; " for it " excited no criticism, and threatened to stifle 
 the enthusiasm of the author." Bell himself says regretT 
 fully that this announcement, from which he expected so 
 much, "failed to draw one encouraging sentence from 
 medical men." But we can hardly blame them very much 
 for this apathy. The systematic ideas of the author, how- 
 ever attractive to himself, might not have the same interest 
 for others ; and his experimental proofs were certainly in- 
 sufficient to command belief on their own merits. Indeed, 
 we now know that they do not really bear the significance 
 which he attached to them. The anterior and posterior 
 nerve-roots are not connected respectively with the cere- 
 brum and cerebellum, and we cannot use them in our 
 experiments to determine the separate functions of the 
 brain. It was, no doubt, a suspicion of this physiological 
 non sequitur that prevented the pamphlet from being appre- 
 ciated as its author had hoped. 
 
 But, notwithstanding this discouragement, Bell afterward 
 returned to the subject with new vigor, and soon came to 
 regard his former work as only the introduction to a more 
 extended system. In his first essay, the brain was the main 
 subject of research, the nerves and their distributions being 
 only secondary; but, in his theory as afterward developed, 
 the nerves and their distributions occupied ^ the prominent 
 place. This matter, in 18 14, was already, he says, "ripen- 
 
 • Reprint in the Journal of Anatomy and Physiology, vol. iii, p. 162. 
 
AND THE THEORY OF SIR CHARLES BELL. 97 
 
 ing in his head ; " and in his lectures on the nerves for that 
 year he promises to "lay open a fine system." Like his 
 anatomy of the brain, the system increased in importance 
 the more he thought about it. Year by year he enlarged 
 its proportions, and seemed to anticipate from it greater 
 results than ever. He gradually brought it into the form 
 of a series of communications to the Royal Society. In 
 1 8 19 he regarded it as nearly complete, and fully worth the 
 labor it had cost, containing, as he believed, the materi^s 
 of a grand system, destined to "revolutionize all we know 
 of this part of anatomy, more than the discovery of the cir- 
 culation of the blood." By the time the first paper was 
 ready for presentation he was abundantly satisfied with it, 
 and declared that he had made " a greater discovery than 
 ever was made by any one man in anatomy." 
 
 In this communication,' Bell presented the main prin- 
 ciples of his new arrangement of the nervous system, with 
 special reference to the nerves of the face. The paper had 
 been prepared by its author with much care, and he offered 
 it to the Royal Society as the result of several years of 
 thought and investigation. 
 
 This time he had no reason to be disappointed, as the 
 essay attracted everywhere attention and approval. In 
 speaking of a reception which he attended soon afterward, 
 " My paper," he says, " has done me as much good as if 
 I had bought a new blue coat and figured French black silk 
 waistcoat. One gentleman called it the first discovery of 
 the age." He received a number of complimentary letters 
 in regard to it, which, he says, were enough to show that he 
 was " not a visionary " on the subject. " It will hereafter," 
 he adds, " put me beside Harvey." ^ 
 
 ' Philosophical Transactions of the Royal Society. London, 1821, p. 398. 
 ' Letters of Sir Charles Bell, p. 272. 
 
98 NERVOUS DEGENERATIONS 
 
 This paper of 1821 well deserved the praise bestowed 
 upon it, for it contained the announcement of Bell's most 
 lasting and undisputed discovery ; namely, that the facial 
 nerve, ox portio dura of the seventh pair, was not a nerve 
 of sensibility, but a channel for muscular action and the 
 nervous medium of expression in the face. The importance 
 of this discovery, both scientific and practical, was abun- 
 dantly manifest ; and it was sustained by direct and satis- 
 factory experiments on animals, as well as by observations 
 on man. It is evident that Bell did not get at the whole 
 truth in regard to this nerve ; for he represented its action 
 as limited to the involuntary movements of respiration and 
 expression, and considered the voluntary motions of the 
 face and lips as still provided for by the fifth pair. But it 
 is very seldom that all the details of so complex a subject 
 are mastered by one person, or at one time ; and the primary 
 facts of the motor character of the facial nerve and its 
 insensibility, as contrasted with the extreme sensibility of 
 the fifth pair, were then fully established on incontestable 
 evidence. 
 
 Bell, however, was much more interested in the general 
 plan of his classification than in any of its details, which he 
 valued mainly as illustrations or proofs of the system as a 
 whole. He continued its development in his communica- 
 tions to the Royal Society ; and it was afterward embodied, 
 with some necessary modifications, in his "Nervous System 
 of the Human Body," published in 1 830. 
 
 Bell's conception of the arrangement of the nerves was 
 this : All the nerves of the cerebrorspinal system were 
 divided into two great classes or groups. The first group 
 was that of the regular, original, or symmetrical nerves ; 
 namely, the thirty-one pairs of spinal nerves and the fifth 
 pair of cranial nerves. All these nerves arise by two roots, 
 
AND THE THEORY OF SIR CHARLES BELL. 99 
 
 on one of which is a ganglion ; they pass out regularly to 
 successive divisions of the body ; they are all subservient 
 to voluntary motion and common sensibility ; they are dis- 
 tributed to every part of the frame, but are symmetrical 
 and simple in their arrangement. The second group was 
 made up of the irregular or superadded nerves. These do 
 not arise by double roots, and have no ganglia at their 
 origins : they come off from the sides of the medulla ob- 
 longata and upper part of the spinal cord ; and, instead of 
 being distributed in regular ordeir to successive parts of the 
 frame, are sent to remote organs, which they combine in 
 functional activity. They therefore have the character of 
 being superadded, for a special purpose, to the original 
 system of regular nerves. They constitute the great group 
 of respiratory nerves, which are distributed to a variety of 
 organs, and, instead of going out on each side straight to 
 their destination, often pass through the body in a longi- 
 tudinal or oblique direction. They are, — 
 
 First, The facial, portio dura of the seventh pair, respi- 
 ratory nerve of the face. 
 
 Second, The glosso-pharyngeal nerve, distributed to the 
 tongue and pharynx. 
 
 Third, The par vagum, or pneumogastric, the. nerve of 
 the lungs, heart, and stomach. 
 
 Fourth, The spinal accessory, or superior respiratory 
 nerve of the trunk, distributed to the sterno-mastoid and 
 trapezius muscles. 
 
 Fifth, The sublingual, or the nerve of articulation. 
 
 Sixth, The phrenic, or great internal respiratory nerve. 
 
 Seventh, The long thoracic, or external respiratory nerve 
 of the trunk. 
 
 Eighth, The fourth nerve, or patheticus, distributed to 
 the superior oblique muscle of the eyeball. 
 
100 NERVOUS DEGENERATIONS 
 
 These are the nerves which produce the appearance of 
 irregularity or confusion in the nervous system; because 
 they often cross the track of the symmetrical nerves, and 
 are distributed to organs already supplied by them. 
 
 This last fact gives the key to the functional peculiarity 
 of the superadded nerves. According to Bell, an organ 
 which performs only a single function has but one nerve 
 supplied to it ; and, whenever an organ receives nerves from 
 two or more sources, it is because it performs as many dif- 
 ferent functions. This explains why certain muscles, like 
 the sterno-mastoid and trapezius, already supplied with 
 nerves from the regular or symmetrical system, also receive 
 branches from the respiratory system. The former nerves 
 enable them to execute the ordinary acts of voluntary 
 motion: the latter bring them into occasional involuntary 
 unison with the act of respiration. This is illustrated in a 
 still more striking manner by the two nerves distributed to 
 the face ; namely, the fifth pair, supplying the face with 
 sensation and voluntary motion," and the facial nerve, or 
 seventh, a superadded nerve, which controls the involuntary 
 motions of the face in breathing,^ or, as he says, "when 
 the muscles of these parts are in associated action with the 
 other organs of respiration." 
 
 The respiratory nerves, however, come into play, not only 
 in the motions of respiration proper, but in all those con- 
 nected with the entrance and exit of air from the lungs ; as 
 in speaking, singing, coughing, gasping, or sneezing. They 
 are also the agents in all movements of expression, or the 
 emotional affections of the frame. This is especially 
 marked in the seventh pair, which regulates the involuntary 
 changes of expression in the face. But it applies also to 
 
 ' Philosophical Transactions, 1821, pp. 410, 411, 413, 417; and 1822, p. 284. 
 ^ Ibid., 1821, pp. 406, 410, 414. 
 
AND THE THEORY OF SIR CHARLES BELL. lOI 
 
 the manifestations of emotion in other parts ; as in the 
 hurried respiration of anxiety, the retardation or quickening 
 of the heart, and the sobbing of the diaphragm in grietfi 
 excitement, or depression. Under every strong impulse, 
 the central organs of respiration are stimulated or disturbed, 
 and thus bring into associated action all their subordinate 
 parts as organs of expression. 
 
 Furthermore, the nerves of respiration, wherever they 
 may be, have greater vitality than other nerves; for the 
 movements connected with this function continue to be 
 performed after sensibility and volition have disappeared. 
 Thus these nerves form a great system by themselves, dis- 
 tinguished from the ordinary or regular nerves by their 
 mode of origin, their functions, their distribution, and their 
 vitality. 
 
 Evidently there was much of real value in these observa- 
 tions. They placed in strong relief the fact of associated 
 respiratory motions. The expansion and collapse of the 
 nostrils or lips, accompanying the action of the thorax, are 
 occasional in man, constant in some animals, and are always 
 in proportion to the intensity of respiration. They are 
 truly respiratory motions, as much so as those of the dia- 
 phragm. The sterno-mastoid and trapezius muscles are 
 also brought into action whenever breathing is impeded or 
 laborious. The classification which Bell constructed on 
 this basis, and illustrated with so much ingenuity, has a 
 certain charm about it, and is plainly marked with the 
 talent and originality of its author. But, even as a system, 
 its joints do not all bear inspection ; and it contained from 
 the outset certain defects, which became after a time plainly 
 perceptible. 
 
 Bell showed by his experiments and observations that the 
 seventh nerve controls the involuntary motions of expres- 
 
102 NERVOUS DEGENERATIONS 
 
 sion and respiration in the face, and that these motions are 
 abolished by its division or injury. If he had accepted this 
 fact at its own value, and had assumed nothing further, he 
 would have been secure ; but he believed, in accordance 
 with his system, that these involuntary movements were 
 the only ones under control of the seventh nerve, and 
 that sensibility and volition were provided for by the fifth 
 pair. This idea influenced his mind to such an extent, that 
 he was led to conclude, after division of the fifth pair alone, 
 that the voluntary movements of the lips were paralyzed, 
 while those of respiration continued.' Magendie, on the 
 other hand, who believed in nothing but direct experiment, 
 repeated this operation on the fifth pair, and declared that 
 he could not perceive any paralysis of the lips produced in 
 consequence.^ We now know that he was right, and that 
 the fifth pair does not animate any of the superficial muscles 
 of the face. That being true, according to Bell's principle, 
 there ought to be two other nerves distributed to this part, 
 — one for its voluntary, the other for its respiratory func- 
 tions; but, in fact, it has only the seventh pair, which 
 serves for both. 
 
 Bell's classification of the respiratory nerves, with regard 
 to their origin, is by no means perfect in its details. These 
 nerves were said to differ from the others in having no 
 ganglia at their roots, and in originating from an interme- 
 diate tract on the sides of the medulla and spinal cord. 
 But both the pneumogastric and glosso-pharyngeal nerves 
 have ganglia at their roots, which are as real, though not 
 quite so conspicuous, as the Gasserian ganglion of the fifth 
 pair. Again : the origin of nerve-roots, in a nearly contin- 
 uous line, from the lateral tract of the medulla and spinal 
 
 ' Philosophical Transactions, 1821, p. 413. 
 
 " Journal de Physiologie. Ann& 1821. Tome i. p. 387. 
 
AND THE THEORY OF SIR CHARLES BELL. I03 
 
 cord, is certainly a marked feature in the glosso-pharyngeal, 
 pneumogastric, and spinal accessory nerves. On the other 
 hand, it cannot be asserted, with any plausibility, of the 
 facial, sublingual, and patheticus. 
 
 The last-named nerve was associated with the respiratory 
 system, because it was regarded as causing the upward 
 rolling of the eyeball in involuntary movements and emo- 
 tional expressions. Every thing connected with this sub- 
 ject had for Bell a great attraction. His book on the 
 " Anatomy of Expression " was his earliest publication in 
 London, and first called attention to him as a man of ability. 
 He gave lectures on the same topic to professional artists ; 
 and the exercise of his talent in painting and modelling 
 was always for him a source of pleasure in connection with 
 his anatomical pursuits. This probably accounts for the 
 rather forced amalgamation, in his theory, of the functions 
 of respiration and expression. 
 
 But how does it happen that Bell omitted from his res- 
 piratory system the intercostal muscles and their nerves } 
 One would think they had some claim to be considered as 
 part of this great apparatus. They are constantly at work, 
 and keep time with the diaphragm and lungs more steadily 
 than any other outlying organs of respiration. But the 
 intercostals belong to the regular symmetrical system of 
 nerves, originating from the spinal cord with double roots 
 and all the other features of their ckss. The author 
 ignores this difficulty almost entirely, or alludes to it only 
 so far as to surmise that the branches of these nerves 
 which influence respiration are, "in all probability," derived 
 from the same lateral tract of the spinal cord.' But there is 
 not the least evidence adduced in support of this probability, 
 and the assumption looks very much like reasoning in a 
 circle. 
 
 ' Philosophical Transactions, 1822, p. 287. 
 
104 NERVOUS DEGENERATIONS 
 
 The controversy once carried on as to the exact signifi- 
 cance of Sir Charles Bell's doctrine and discoveries was 
 due, in great measure, to the singular obscurity of his style, 
 and his 'indefinite manner of statement. These defects 
 were habitual with him as a writer, and in many instances 
 are extremely marked. There are few pieces of harder 
 reading than the preface and introduction to his " Nervous 
 System of the Human Body." ■ In attempting to account 
 for this obscurity, the reader is sometimes in doubt whether 
 Bell really has any distinct idea to communicate, or whether 
 he voluntarily stops short of its complete expression. One 
 of these puzzling passages is the following. After speaking 
 of the par vagum and the spinal accessory nerve, he says 
 (p. 47), " Directed in the next place to the portio dura, I 
 wished to answer the question, ' Why does the nerve which 
 supplies certain muscles of the face take an origin and a 
 course different from the fifth nerve, destined to the same 
 parts .' ' Guided by these considerations in my experiments, 
 by inference I concluded, that, on cutting across this nerve, 
 all the motions of the face connected with respiration 
 ceased, and that it had the origin we see, and took its 
 course with the respiratory nerves, because it was neces- 
 sary for the association of the muscles of the nostrils, 
 cheek, and lips, with the other muscles used in breathing, 
 speaking, etc." It is certainly impossible to determine, 
 from the phraseology of this sentence, whether it contains 
 the statement of an experimental fact, or is only the expres- 
 sion of a hypothetical surmise. 
 
 Having enumerated again the various organs of respi- 
 ration, he says (p. 49), "It appears, then, that it is the 
 distance and irregular position of the eye, nostril, mouth, 
 throat, and larynx, and muscles of the neck, which require 
 
 ' First edition. London, 1830. 
 
AND THE THEORY OF SIR CHARLES BELL. lOS 
 
 these diverging and apparently irregular nerves, to connect 
 them with the act of respiration, and without which they 
 would have possessed no more attributes than the nerves 
 of the limbs ; that is to say, sensibility and motion." 
 
 There is nothing in the context to indicate from what 
 point the eye, nostrils, mouth, throat, and larynx are " dis- 
 tant," or why they should be considered as more " irregular" 
 in position than the limbs. 
 
 One of the most curious instances of this peculiarity is 
 a passage in one of Bell's earlier letters, describing his new 
 system of the anatomy of the brain; and I think it hardly 
 probable that any one now present will be able to under- 
 stand exactly what he means by it. " I consider," he says,' 
 "the organs of the outward senses as forming a distinct 
 class of nerves from the other. I trace them to corre- 
 sponding parts of the brain, totally distinct from the origins 
 of the others. I take five tubercles within the brain as 
 the internal senses. I trace the nerves of the nose, eye, 
 ear, and tongue to these. Here I see established connec- 
 tions. Then the great mass of the brain receives processes 
 from these central tubercles. Again • the greater mass of 
 the cerebrum sends down processes, or crura, which give 
 off all the common nerves of voluntary motion, etc. I 
 establish thus a kind of circulation, as it were. In this 
 inquiry I describe many new connections. The whole 
 opens up in a new and simple light : the nerves take a 
 simple arrangement ; the parts have appropriate nerves ; 
 and the whole accords with the phenomena of the patholo- 
 gy, and is supported by interesting views'^ 
 
 This indefinite style of expression extends, as in one of 
 the passages just quoted, even to the description of experi- 
 ments and their results. It is usually thought essential in 
 
 • Letters of Sir Charles Bell, p. 117. 
 
Io6 NERVOUS DEGENERATIONS 
 
 reporting experiments,, especially if bearing on new ques- 
 tions in physiology, to state all the particulars> so that the 
 reader may form for himself some estimate of their value. 
 Bell habitually neglects this useful precaution. He gener- 
 ally omits all mention of the details of the operative pro- 
 cedure, often that of the species of animal employed,' and 
 sometimes even whether it were living or dead at the time 
 of the experiment. The consequence is, that doubts have 
 been entertained on these points in regard to some of his 
 most important investigations. 
 
 The truth is. Bell had no real faith in experimentation as 
 a source of knowledge. He preferred to make his deduc- 
 tions, in the first place, from the details of anatomical 
 structure ; employing experiments afterward to " prove " 
 or "confirm" them, or to impress his convictions on the 
 minds of others. This is abundantly evident from his own 
 express declaration in various parts of his works, as well as 
 from the method pursued in originating and carrying out 
 his investigations. With him, the conception of a system 
 was the beginning and the end of the mental process : its 
 experimental evidence was only an intermediate episode. 
 For this reason. Bell would hardly be considered, at the 
 present day, as a physiologist. Indeed, he never speaks of 
 himself as such, but always as an "anatomist," whose 
 whole pleasure is in "investigating structure ;",and even 
 his new doctrines and ideas he designates as " discoveries 
 in anatomy." 
 
 This explains, in some degree, his undue estimate of the 
 two methods of inquiry. He had so high a regard for 
 the results of anatomical research, that he believed them 
 capable of also solving questions in physiology. Already, 
 in 1808, three years before printing his "Idea of a New 
 Anatomy of the Brain," he " is sure," he says, " that he is 
 
AND THE THEORY OF SIR CHARLES BELL. 107 
 
 correct ; " and that was before he had made a single experi- 
 ment. And long afterward he declares that the "few 
 experiments" which he has made "were directed only to 
 the verification of the fundamental principles on which the 
 system is established." But the result of this method has 
 been exactly the reverse of what he anticipated. The ex- 
 perimental observations, which he undervalued, form the only 
 part of his system which has remained ; while the attrac- 
 tive and harmonious classification, which he constructed 
 with so much ingenuity on the basis of anatomical deduc- 
 tion, has now lost its importance and almost its place in 
 medical literature. 
 
 The value of the experimental method in medical science 
 cannot be measured by the direct results of any particular 
 discovery. It is true that these discoveries are often of 
 great importance, and increase largely the fund of our 
 medical knowledge. They possess, moreover, a vitality 
 which distinguishes them in a marked degree from the 
 ephemeral products of scientific hypothesis. When a 
 hypothetical system has served its time, it disappears, and 
 is replaced by a different one ; but the knowledge derived 
 from experiment remains serviceable long after its novelty 
 has passed away. The experimental observations of Galen 
 on the recurrent laryngeal nerves and on the functions of 
 the arteries as blood-vessels are as conclusive now as when 
 he first made them, and retain at this day their full value. 
 They have lasted for over seventeen centliries, and have sur- 
 vived, during that time, all the fluctuating medical systems 
 of solidism and fluidism, of animism, vitalism, archeism, 
 and iatro-mechanism. The information which they im- 
 parted was a reality, and is neither destroyed nor impaired 1 
 by the lapse of time. 
 
I08 NERVOUS DEGENERATIONS, ETC. 
 
 But the benefits of an expefimental discovery ejctend far 
 beyond its immediate limits. When a new fact has been 
 established in anatomy or physiology, it is impossible to 
 say what bearing it will have on other facts not yet dis- 
 covered ; and in the history of medicine there are many 
 
 1 instances of curious observations, which remained imperfect 
 
 I and apparently barren until subsequent discoveries invested 
 them with an unexpected importance. It is evident that 
 Galen's detection of the arterial blood-current in the second 
 
 j century was a necessary preliminary to Harvey's complete 
 discovery of the circulation in the seventeenth ; and the 
 
 'lymphatic vessels, discovered in 165 1, were thought to be 
 the agents of a slow and insignificant absorption, until 
 Colin found, two hundred years later, that the daily quan- 
 tity of fluids passing through the thoracic duct was from 
 four to ten per cent of the entire bodily weight. It is 
 almost certain that a genuine investigation, however iso- 
 lated, will produce, some time or other, its legitimate fruit. 
 But, to secure this object, there is one essential requisite; 
 and that is, that experimental research be followed and 
 cultivated for its own results, whatever they may be, with- 
 out demanding immediate returns of a kind that can be 
 designated beforehand, and with entire confidence in the 
 substantial value of this method, which has always been, 
 and will always be, the only source of permanent improve- 
 ment in medical science.