jp g^^ax^E■-jji1' ^^!^^^^5^"3S^ii r?ie formed of the same substance with the white and me- dullary part of the brain and medulla spinalis. I conceive, therefore, that the white part of the medulla spinalis is composed of nervous fila- ments, having their origin or termination at one end in the brain, and at the other in every" part of the medulla; and that it is in the cinericious part of the medulla that both the spinal nerves and the principle that animates them arise. The anatomical researches of Mr. Gall, appear to me, to give much weight to this opinion. The action of the brain upon every part of the medulla, does not only produce the effect INTRODUCTION. g of determining and regulating the motions, but it appears to increase their energy. The motions are always weaker in the animal decapitated than in that which is not, unless the end of the me- dulla be immediately touched, for then the mo- tions are very strong and even convulsive. It is true, that the weakness of these motions may also pardy be owing to the medulla being al- ways in a morbid state after decapitation. These intimate relations between the brain and the me- dulla spinalis, will aid in accounting for cer- tain facts which appear at first very difficult to be reconciled with my experiments. Such is the palsy of one whole side of the body pro- duced by causes which affected the brain alone. But though no means of reconciling them should be perceived, it would be no less correct, that ' an affection limited to the brain may deprive one half of the body of sensation and motion, than that sensation and voluntary motion may be maintained in a decapitated animal. However opposed these facts appear to be, it must be re- collected that two facts well ascertained can never destroy each other, and that the apparent contradiction is produced by some intermediate B ,q INTRODUCTION. cause, some point of contact that has escaped our observation. The unity of self, of which we have the con- sciousness, is another fact which seems to be repugnant to the dissemination of the principle of life through the whole extent of the brain and the medulla spinalis. But it ought to be remark- ed that the connexion and harmony of all the parts of the nervous power are sufficient to pro- duce the sentiment of this unity, though this power is not concentrated in one point. Sup- pose, if I may be allowed this vulgar compari- son, a number of wheels connected by their cogs, they will form one system only; no one can perform any motion unless they all do the same. But let the connexions be interrupted in one or several places, the result will be a variety of parts capable of motion which will be inde- pendent of each other. So if you produce inter- ruptions in the seat of the nervous power, you will thereby establish a variety of centers of sensation entirely distinct. But what is impor- tant to be observed is, that those various centers can never be created but by interruptions caused INTRODUCTION. H by design or accident, and that each of them always supposes the co-existence of a portion of the seat of the nervous power, which is very different from the opinion by which it is admit- ted, that in the natural state, each organ has a centre of sensation and a sort of life peculiar to itself. This opinion, rejected by the soundest theories and the best established facts in phy- siology, had acquired much influence in mo- dern times, when Mr. Cuvier declared himself against it; nothing short of the influence of so justly celebrated a man could arrest its pro- gress. Another question on which I have dwelt but little, was to know in what manner the nerves transmit the action of the nervous power to those parts where they are distributed. Are they only simple conductors, or is there a secretion pro- duced in them of a nature analogous to that which takes place in the brain or in the medulla spinalis? The researches of Messrs. Reil and Prochaska, had rendered this opinion very pro- bable. Mr. Nysten has since shown, that in the most complete palsies, the irritability is preserv- j2 INTRODUCTION. ed in the paralised limbs as perfectly as in those that are sound. I obtained a like result from an experiment which I have often repeated. It con- sists in destroying the lumbar portion of the medulla spinalis of a rabbit not ten days old; it should be chosen of that age, that the circulation may not be stopped, and that it may continue to live. Although in this experiment, the hind part is struck with death, and its nerves can no longer receive any influence from the medulla spinalis, it preserves its irritability, and the thighs may for a long time be made to contract by irritat- ing the sciatic nerves. Hence it appears as if a secretion of a particular principle were made through the whole extent of the nerves. This principle, being once produced, continues of itself, and even after the entire cessation of the circulation, in the same manner as that of the brain and of the medulla spinalis. I had thought that it was through the medium of the nervous principle that the brain and the medulla spinalis exercised their action upon the different parts of the body, without a circulation of their prin- ciple, but by a sort of a shock upon that of the nerves, nearly as sound is transmitted through INTRODUCTION. J3 the air. To ascertain this conjecture, it was necessary to find a nerve which might easily be isolated through a certain extent, and which commanded some function, the interruption of which would be sudden and very apparent, as. soon as the nerve should cease to act. I select- ed the nerve of the eighth pair in kittens. We shall see by and by, that the ligature or section of those nerves in these animals, produces sud- denly all the symptoms of violent suffocation. By detaching them through the greatest part of the neck and by destroying all the vessels which are distributed to them, I expected, if my con- jecture was well founded, that as soon as the principle with which they were imbued at the moment of dissection, should be exhausted, the kittens would experience the same suffocation as if these nerves had been tied or divided. But it was in vain I repeated this experiment seve- ral times; the result never answered my expec- tations; respiration never was disordered in any sensible degree, whilst if one or several hours after having detached the nerves, I divided them, suffocation instantly took place. Nevertheless, I do not wholly give up this hypothesis; for the ]4 INTRODUCTION. neck of cats is of no great length, and besides it is impossible to detach the par vagum through- out that extent. It is possible that the secretion continuing near the thorax, and the head or the vessels not being destroyed, might extend to the dissected portion. This is what I had to add upon the func- tions of the nervous power, and particularly upon that of the brain, to what I have said in my memoirs. The general idea I have of this power is, that its seat constitutes in itself the individual as a living being; all the rest of the organization of an animal only serves to establish a relation between the nervous power and external ob- jects, or to prepare and supply it with materials necessary for its support and nourishment. In the whole range of animals, I perceive only every possible combination of organs capable of sustaining in the nervous power, properties various as these combinations, yet in all intrin- sically the same. Among these combinations, those which are the simplest, and in which the conditions, necessary to the maintainance of the nervous power, exist in all the parts, are sus- INTRODUCTION. 15 ceptible of being divided into portions; and life may continue in each portion as in the whole animal, or rather each portion becomes a new animal. On the contrary, those in which these conditions center in certain parts, do not admit the like divisions with the same success: life cannot continue in the segments which are found separated from these parts, longer than the ner- vous power can subsist of itself without being renewed. My object has been rather to describe the results than enter into any detail, or to multiply their numbers. All the particulars I have given, appear to me necessary to show the order and succession of the phenomena, and to enable the physiologist to ascertain them. I propose to publish, hereafter, the journals of my experi- ments, with all the particulars they contain. I have been more careful in ascertaining the facts than eager to publish them. Nevertheless, I judge it proper to fix their several dates. My researches on the foetus date from 1806. It was only in 1808, that I communicated my first ob- lg INTRODUCTION. servations to the society of the professors of the faculty of medicine of Paris. In these, I com- municated my first notices on decapitation, and on the functions of the medulla spinalis. At the invitation of Mr. Thouret,* I demonstrated publicly before the same society, on the 2d and 16th of March, 1809, that the principle of the life of the trunk resides in the medulla spinalis; and I afterwards repeated the same experiments, on the 16th of April, before Messrs. Chaussier and Dumeril, whom the society had chosen a committee to examine them, and who made their report on the 27th of the same month. The subject was far from being exhausted; I soon after began my researches upon the mo- tions of the heart. Mr. Magendie proved, soon after, by some interesting experiments, that it is by acting upon the medulla spinalis that the poison of the Indians, known under the name of upas tieute, kills animals. Mr. Brodie, a mem- ber of the royal society of London, was desir- ous of ascertaining the temperature and the state * Dean of the faculty of medicine of Paris. INTRODUCTION. ji- of the secretion in animals kept alive after de- capitation. I have repeated the experiments of this author, in what relates to the temperature. The results which he announces did not appear to me as regular as he pretends. Mr. Brodie asserts, that the decapitated animals which are kept alive, cool as rapidly as if they were dead. It is true, that their temperature is consider- ably reduced; but I have always found in kittens that this reduction of temperature is less than after death. The difference has been in my ex- periments, from one to three degrees, (centi- grade thermometer). It is generally less in rab- bits. I found also, that the inflation of the lungs is one of the principal causes of this refrigera- tion; and that generally speaking, all the cir- cumstances which derange or impede respira- tion produce this effect. Thus keeping an animal extended on its back will lower its temperature. My attention is at present engaged in ascer- taining whether, under these different circum- stances, the formation of the carbonic acid in the lungs is diminished, and with a corresponding alteration of temperature. My friend, Mr. Thil- C ,o INTRODUCTION. laye junior, has favoured me with his assistance. The experience of this able natural philosopher, his great dexterity and thorough habit of expe- rimenting, render his co-operation singularly valuable. Several causes had interrupted our labours, and among others, some very expen- sive instruments. Baron Corvisart, first physi- cian to the Emperor, being informed that those instruments were not in the cabinet of natural history of the faculty of medicine, of his own accord, and with his usual munificence, directed them to be sent and placed at my disposal, and he likewise had the goodness to permit me to order the construction of them in the manner I might think most- suitable. It is gratifying to me, to take this opportunity of publicly expressing my gratitude. When these researches shall be Concluded, I propose to review and publish my first experi- ments on foetuses; particularly those made with a view to determine how long a foetus may live without breathing, after its communication with its mother has ceased. INTRODUCTION. JQ Before I close this introduction., I wish in some degree to exculpate the physiologists who make experiments upon living animals, from the reproaches of cruelty, so frequently uttered against them. I do not pretend wholly to justify them. I would only remark, that the most part of those who utter those reproaches may be deserving of the same. For example, do they not go, or have they never gone a hunting? How can the sportsman, who for his own plea- sure mutilates so many animals, and often in so cruel a manner, be more humane than the physiologist who is forced to make them perish for his instruction? Whether the rights we as- sume over those animals be lawful or not, it is certain that few people scruple to destroy, in a variety of ways, such of those animals as cause them the least inconvenience, though ever so trifling; and that we only feed the most part of those that surround us, to sacrifice them to our wants. I can scarcely comprehend that we should be wrong in killing them for our instruction, when we think we are right in destroying them for our food; and especially when, by a refine- 2q INTRODUCTION. ment in gluttony, we kill them after submitting them to painful operations and long tortures. I own that it would be barbarous to make animals suffer in vain, if the object of the ex- periment could be obtained without it. But it is impossible. Experiments upon living animals are one of the greatest lights of physiology. The difference between the dead and the liv- ing animal is infinite. If the ablest mechanician is unable to discover all the effect of a machine after having seen it work, how could the most learned anatomist devise, by the study only of the organs, the effect of a machine as prodi- giously complicated as the body of an animal. To find out its secrets, it is not enough to ob- serve the simultaneous exercise of all the func- tions in the animal, while in health; it is above all important to study the effect of the derange- ment, or the cessation of such or such a func- tion. It is in determining by this analysis what the function of such or such an organ is, as well as its relation with the other functions, that the art of experiments upon living animals consists. But to be able to do it with some degree of INTRODUCTION. 21 precision, it is indispensably necessary to mul- tiply the victims, on account of the variety of circumstances and accidents which may render their result uncertain or inconclusive. I should be tempted to say of physiological experiments, what has been said of charities: perdenda sunt multa; ut semelponas bene. Seneca. EXPERIMENTS OK THE PRINCIPLE OF LIFE. Of the faculties peculiar to animals, those by which they are eminently characterized are sen- sation and motion; and it may be said, that the real end of organization in an animal, is to pro- duce and maintain these two faculties. What- ever the internal or external means, the secret or apparent springs, which nature employs; and whatever the actual situation of those means, and of those springs,—as soon as a being feels and moves, it is a living animal endowed with the sense of its own existence. To know in what consists the essence of life, it will be neces- sary to ascertain what is the precise condition, 24 EXPERIMENTS ON THE in the organization of animals, on which sensa- tion and motion depend. In this inquiry, how- ever, two circumstances are to be determined: first, the exact nature of this condition; secondly, the parts to which it is confined, or its seat. For instance, admitting that sensation and motion are produced by a particular principle, the result of organization, we must inquire, what is the nature and the seat of this principle? Both these questions have given rise to various specula- tions; and to mention only the latter question, though it appears capable of a more ready solu- tion than the former, yet no hypothesis has hitherto been offered fully satisfactory or adapt- ed to all the phenomena. It might be imagined that the principle of sensation and motion resided in every part of the body, as all seem more or less to participate of these two faculties. But observation having shown that the section of a nerve, in any part of its course, instantly deprives of sensation and motion all the parts to which the inferior por- tion of the divided nerve is distributed, it neces- sarily follows that the sentient principle does PRINCIPLE OP LIFE. 25 not reside in the part which receives the impres-- sion, and likewise that the power causing motion, exists not in the part which moves; but to dis- cover itsiseat, it is necessary to rec.; to the origin of the nerves. Now as all the nerves arise from the brain and the spinal marrow, the source of life has been supposed to be derived from the brain and spinal marrow. A multitude of facts prove, on the one hand, that the destruc- tion or even certain wounds of the brain, cause sudden death; on the other, that the transverse section of the spinal marrow, in any part of its course, always paralyzes the parts below the sec- tion, whilst all those above, continuing their communications with the brain, preserved both sensibility and motion. Moreover, the spinal marrow has been considered by anatomists only as a large nerve arising from the brain, in the same manner as all those which pass through the foramina of the cranium, and which like them are divided at intervals, in order to supply the intervertebral nerves;—in short this spinal marrow was considered as a mere bunch of nerves supplying the trunk, as it was often call- ed. The brain therefore was considered as a D ^g EXPERIMENTS ON THE center of the nervous power, and consequently as the only seat of the principle of life. This opinion was carried still further. The unity of self, the metaphysical ideas referred to it, and the observation, that certain parts of the brain might be wounded, and even de- stroyed with impunity, led to the conclusion, that this viscus in its entire capacity was not the seat of this principle, and that there must be a defined spot where all sensation terminated, and whence all motion received its impulse; and this place, designated under the name of sensorium commune, or the seat of the soul, was for a long time an object of inquiry among physiologists. But the object was not obtained by these in- quiries; for in proportion as known facts have been examined, and observation has been ex- tended, has the difficulty increased, of recon- ciling all these facts with the theory which places exclusively in the brain, taken in all its parts, the principle of sensation and animal motion. Thus it could not be conceived, agree- ably to this opinion, why reptiles, such as the PRINCIPLE OF LIFE 27 tortoise, salamander, &c, preserve life for whole months after decapitation; nor why animals of inferior classes present similar or even more ex- traordinary phenomena. It was still more diffi- cult to understand, why the duration of life in those animals, varies to such a considerable de- gree according to the mode in which the brain has been removed; why for instance the tortoise, from which Redi had taken this viscus, by opening the cranium, had survived the opera- tion several months, whilst those whose heads he had cut off below the occiput had only sur- vived it a certain number of days (a). For the difference is not produced by the hemorrhage as might be supposed. To obviate these diffi- culties, it has been asserted that the opinion in question was only established upon observations made upon warm-blooded animals, that it was only applicable to them, and that in the cold- blooded ones, the nervous power was subjected to other laws. But a considerable number of facts observed in the warm-blooded themselves, seemed to militate against this explanation. (a) Opere di Frances Redi, 1741. Tom. I. p. 78, and torn. II. p. 194. go EXPERIMENTS ON THE It is a well established fact, that birds conti- nue alive and even walk and run after their heads have been cut off. The fact has frequently been quoted of the emperor Commodus, who, whilst ostriches were running in the circus, amused himself by cutting off their heads with arrows, in the form of a crescent. These animals were not prevented from running as before, and only stopt at the end of the course. Several physio- logists have obtained a like result, by decapita- ting turkeys, (a) cocks, (b) ducks, (c) pigeons, (d) &c, hence as regards these animals, a par- ticular exception must be made in the laws re- gulating the nervous power (?), and the received theory remains only applicable to man and other mammiferous animals. In the latter the phenomena appear to corres- pond with this theory; whether after decapitation (a) Lametrie, (Euvres Philosoph. 1751, p. 56. (b) Kaauw Boerhaave. impet. faciens. No. 331, p. 262. —Urb. Tosetti, Mem. sur les part, sensi. et irritab. torn II. p. 194. (c) M. Cuvier, Lecons orales. (rf) Woodward, cite par Haller. (; no hemorrhage. Pulmonary inflation not performed. The breast opened at eighteen mi- nutes; pulmonary veins red. CASE VI. Medulla Lumbaris destroyed.—Circulation ceases two minutes after. Upon another rabbit. Immediate destruction of the medulla lumbaris; respiration disordered but without gaping; motions of the heart irregular, but yet tolerably distinct. The animal supports itself upon its fore feet, and carries its head well. At one minute and a half, totters; and can scarcely support it. At two minutes, falls upon its side, and respiration stopped at once; a few seconds after, gapings accompanied with move- ments of the thorax are observed. About that time, the motions of the heart are no longer dis- tinct. Sensation ends at three minutes and a half, and the gapings at about four. Pulmonary inflation begun at three minutes and two thirds; no effect. Carotids are flat and empty at five minutes. One leg cut off at one minute and a half, bleeds a little; blood red: the thigh cut at PRINCIPLE OF LIFE. JQ5 three minutes does not bleed; nor does that cut off at seven minutes. Inflation discontinued at ten minutes. Pulmonary veins red. I will not here repeat what I have said upon the value of the signs, drawn from the colour or absence of the hemorrhage, of the fulness, colour or vacuity of the carotids, of the facility or impos- sibility of feeling the motions of the heart through the parietes of the thorax, &c. If we compare what they are, after the section of the medulla at the occiput, and even after decapitation, with what they become after the total or partial de- struction of the spinal marrow, there will I think, remain no doubt, that in this last case, whenever life ceases, in those parts of the animal in which the destruction of the medulla had not occa- sioned death, it is only because this destruction has stopped the general circulation. But I ought to remark, that among the signs calculated to show the state of the circulation, the duration of sensation, and that of the gapings deserve the greatest attention. We have just observed, that in the tenth and twentieth day, as in the first day after birth, these durations coincide with O 106 EXPERIMENTS ON THE those which take place after the excision of the heart; which is the more striking as they dif- fer in a remarkable manner, especially from the first day after birth, from that produced by as- phyxia. (See the above table.) I add that a con- tinuance of sensation, and that of the gapings, are the signs which are most generally applica- ble to all species and ages. In dogs, and espe- cially in cats, under the age of five days, it often happens that all the other signs are insufficient for determining whether the circulation is or is not stopped, after the destruction of the spinal marrow; the continuance of the gapings alone can decide the question. The attentive reader has doubtless observed, in the cases I have just recited, that the pulmo- nary inflation sometimes produces in the caro- tid arteries a small stream of red blood, even when all the other signs indicate that the circu- lation is stopped, and when there ought not to exist any but black blood in the pulmonary veins or in the left cavities of the heart. This feet re- quires explanation. PRINCIPLE OF LIFE. IQ.7 Whenever we proceed to the destruction of the spinal marrow near the occiput, the inspira- tory motions of the thorax being annihilated at the instant when the medulla is disorganized in that part, and before the destruction is so far effected as to stop the circulation, the asphyxia always takes place before the circulation ceases, and consequently the pulmonary veins and the left cavities of the heart contain black blood, in the same way as the right cavities do at the mo- ment when the pulmonary inflation is attempted, after the destruction of the spinal marrow. In this state of things, if red blood issues through the carotids during the inflation, arterial blood must have been formed in the lungs, and that blood must have passed from the pulmonary veins through the left cavities of the heart, and afterwards into the aorta. The question then is: whether this fact indicates the remains of the circulation, or whether the pulmonary inflation can determine the formation of arterial blood after death, when circulation is entirely stopped. For this purpose I took two rabbits twenty days old; in one I destroyed the whole source of the nervous power", by means of a probe introduced jQg EXPERIMENTS ON THE through the cranium, which I pushed through the whole length of the vertebral canal. The other I destroyed by asphyxia, by separating the spinal marrow near the occiput. I left them un- disturbed for forty-five minutes, at the end of which time I opened the thorax; and, after as- certaining that the pulmonary veins in both were black; that the little blood contained in the left auricle was black also; that all the cavi- ties of the heart were at rest, and even that they appeared no longer irritable, at least by the ac- tion of the scalpel; I inflated the lungs. By de- grees, the pulmonary veins and afterwards the left auricle assumed a fine red colour, but no motion of the heart was manifested. Hence it is evident, that the formation of arterial blood may take place in tfce lungs, even when the cir- culation is entirely stopped by any cause what- ever. Let us now suppose that the inflation of the lungs is performed, not as in these two ex- periments, three quarters of an hour after death, but at the instant when the circulation has stop- ped, the irritability of the heart still continuing; each inflation, by diminishing the capacity of the lungs, will express, as from a spunge, the arte-, PRINCIPLE OF LIFE. 109 rial blood from the pulmonary veins into the left auricle; and this blood, which all the experi- ments on asphyxia point out to be the most powerful stimulus of the cavities of the heart, will sufficiently increase the weak contractions of the left ventricle to force it into the carotids; but, as might be expected, only in a very small quantity, insufficient to fill them, or even to give them a round shape; finally, this small stream of red blood is of but short duration, and the caro- tids are soon left empty, because the weakness of the irritable motions of the heart quickly in- creases. This fact, therefore, does not imply the the existence of circulation, and is not in op- « position to the other signs I have already mentioned. It will be perceived, from what I have just stated, why I so carefully noted, in my experi- ments, the colour of the pulmonary veins on opening the thorax. Indeed this colour indi- cates the state of the circulation at the moment when the pulmonary inflation was discontinued. It is evident that whenever those veins are of a red colour, it is a proof that the circulation was 1 jq EXPERIMENTS ON THE stopped, otherwise they could not have remained red, since the blood from the pulmonary artery and the right cavities of the heart would have continued to pass through them. On the con- trary, when they are found black, it is in gene- ral a sign that the circulation was not stopped; but this last case is liable to some exceptions, especially in the ages when the foramen ovale is not closed. It is therefore demonstrated, that the destruc- tion of the spinal marrow suddenly stops the circulation, and that consequently the motions of the heart derive all their power from the me- dulla spinalis. Those which still subsist, either after this destruction, or after the heart has been freed from the action of the nervous power in any other manner, and which have deceived Haller and the authors of his school, are mo- tions without power, and perfectly analagous to the irritable motions, observed in the other muscles for a longer or a shorter time after death. In the latter, those motions only take place when the muscle or the nerve distributed to it, is directly stimulated; and one stimulus PRINCIPLE OF LIFE. Jll only produces one motion. In the heart, the motions are repeated spontaneously, because the blood it contains is its natural stimulus. It is further demonstrated, that the heart receives the source of its power indiscriminately from every part of the spinal marrow. Of the two modes of action, which each portion of the me- dulla exercises upon life, one by which it consti- tutes essentially all the parts which receive their nerves from it, the other by which it contributes to maintain it in the rest of the body, the latter therefore depends upon the powerful influence which it exercises upon the motion of the heart. Thus we find the apparently strange effects of the partial destruction of the spinal marrow ac- counted for. And this conclusion I had drawn from my first experiments: that two conditions are sufficient to maintain life in any one portion of an animal, i. e. the integrity of the correspond- ing spinal marrow; and the continuation of the circulation, requires no further confirmation. For it is evident that, if we cannot maintain life in a part of an animal after having occasioned death in the rest of the body, it is solely because IJ2 EXPERIMENTS ON THE one of these two conditions has been destroyed. Whence it must be concluded, that it would in all cases be easily accomplished, if we could find the means of preventing the circulation from stopping, after we have destroyed a portion of the spinal marrow. Now we have this mean. It consists in limiting by ligatures, made on the arteries, the extent of those parts to which the heart distributes the blood. We have just observed that, generally speak- ing, when the rabbits have reached or gone be- yond the age of twenty days, the destruction even of the lumbar portion of the spinal marrow destroys them in the space of three or four minutes, by stopping the general circulation at the end of one or two minutes. We have seen also, in the recapitulation of my first ex- periments, that the ligature on the aorta by intercepting the circulation through the whole portion of the spinal marrow, which is posterior to the ligature, destroys sensation and motion in all the parts which receive their nerves from that portion of the medulla, which then is for those parts of no use, and as if it did not exist, or as PRINCIPLE OF LIFE. 113 i,f it had been destroyed. Hence it might be infer- red that, by tying the aorta about the last dorsal vertebra, the general circulation ought to stop one or two minutes after the lumbar medulla should, by the effect of this ligature, have lost its vital action. But on the other hand, the ligature of the aorta, necessarily producing a great change in the general circulation, since the parts which receive the blood from the heart, in the greater circulation, are greatly reduced in number, while the lesser circulation continues the same, it was evident that, on that account, the annihilation of the vital action in the lumbar portion of the medulla spinalis, by the ligature of the aorta, does not offer an exact parallel with that pro- duced by the destruction of that portion of thg medulla spinalis. This difference of the results, in these two cases, could only be determined by experiment. Under these circumstances, I performed anew the ligature of the abdominal aorta, by opening the belly of a rabbit thirty days old. I passed a thread under the aorta, and tied it immediately below the cceliac artery, which nearly GorreS* P , j4 EXPERIMENTS ON THE ponds with the begining of the lumbar vertebra?. Motion and sensation disappeared in the hind parts about two minutes and a quarter; but the fore part continued alive. The animal supported itself on its fore feet, carried its head well, and respiration was performed with ease. Fifteen minutes after, it was still in the same state; the flaccidity and absolute insensibility, and in a word the apparent death of all the posterior parts, left no doubt, that the lumbar portion of the medulla spinalis had entirely lost its action, and no longer contributed in any degree to the maintenance of the circulation. Nevertheless, to obtain a direct proof, I destroyed it at this period of fifteen minutes. The animal appeared per- fectly sensible, upon the introduction of the probe in the vertebral canal, between the last dorsal and the first lumbar vertebra?; but it ma- nifested no further signs of pain, the moment the instrument had penetrated as far as the first lum- bar vertebra; and this destruction, which, at the instant when it is performed, is always accom- panied with strong convulsions in the hind part, when the influence of the spinal marrow is un- impaired, did not produce the slightest motion; PRINCIPLE OF LIFE. 115 a certain proof that all this portion of the me- dulla spinalis was dead. Accordingly, the ani- mal continued to live for the fifteen ensuing minutes, after which it was submitted to ano- ther experiment. It is evident that the ligature of the aorta had given it the power of surviving the destruction of the lumbar portion of the me- dulla spinalis. It still remained a question, whether it would be the same with the other portions of the me- dulla spinalis. I mean, whether the influence of such portions could be destroyed by ligature, without stopping the general circulation. We have seen, that although the different portions of the spinal marrow contribute to the powers of the heart, the influence of the cervical por- tion appears to be the most considerable, at least in rabbits. The immediate destruction of that portion is constantly and suddenly mortal in those animals, when they are older than ten days; and before this age, they can scarcely out- live it for a very few minutes. It was therefore a very important point to be ascertained, whe- ther k were possible to destroy the cervical por^ Hg EXPERIMENTS ON THE tion of the medulla spinalis, in a rabbit of thirty days, without instantly killing it. But the only ar- teries in the neck, that can be tied, are the caro- tids, and as these can be supplied by the verte- bral, a ligature made on them is not always suffi- cient to insure the success of the experiment. Considering the conditions which must be com- plied with, to insure success, it appeared to me that the safest way was to decapitate the animal, the only operation capable of wholly intercepting the circulation in the head, and in a part of the neck. My conjecture was confirmed by the experi- ment. Seven times did I destroy the cervical portion of the medulla spinalis, in rabbits of thirty days, after having decapitated them; and yet the circulation was not stopped in any one. The following are the particulars of those ex- periments. The spinal marrow divided near the occiput with a needle.—Pulmonary inflation commenc- ed at three minutes and interrupted at four, for the purpose of tying one of the carotids, together PRINCIPLE OF LIFE. 117 with the corresponding internal and external jugular veins;—resumed at five minutes, then discontinued at six, to tie the carotid and the jugular veins on the other side;—resumed again at seven minutes, and interrupted at eight for one minute more, to separate the aspera arteria from the larynx, and to separate the head with scissors at the first cervical vertebra;—at twelve minutes, the animal being perfectly alive, sen- sible and even performing spontaneous move- ments, all the cervical portion of the spinal mar- row was destroyed. The inflation, which had been discontinued for this operation, was renew- ed at thirteen minutes; motion and sensation appeared suppressed in the fore feet, but per- fect in the thorax and in the hind part, and still continued at twenty-four minutes, that is to say, twelve minutes after the destruction of the cer- vical portion of the medulla spinalis; when the probe was again introduced into the vertebral canal, and the dorsal portion of the medulla spi- nalis, was destroyed, as far down as the eighth vertebra of the back. All the signs of life ceased entirely in the hind part, a little before twentv- five minutes and a half, and could not be ex- 1 lg EXPERIMENTS ON THE cited, though the pulmonary inflation, resumed at twenty-five minutes, was continued to thirty- two; a thigh cutoff at twenty-seven minutes did not bleed. These particulars clearly show, that the circulation continued after the destruction of the cervical portion of the spinal marrow; but that it suddenly stopped upon the destruction of the anterior two thirds of the dorsal portion. The other six experiments were made nearly upon the same plan. In all I destroyed the cervi- cal portion of the spinal marrow at once. But in some, instead of destroying at once the dorsal portion of the medulla spinalis, as far down as the eighth vertebra of the back, I only at first destroyed it as far down as the fourth inclu- sively; then, five minutes after, as low as the eighth; and finally, after five other minutes as low as the first lumbar vertebra; this produced in the results a difference worthy of remark. We have just observed that, by destroying the dorsal portion of the medulla spinalis as low as the eighth vertebra at once, the circulation was stopped instantaneously. But it was not so when PRINCIPLE OF LIFE* 119 this portion was successively destroyed at differ- ent times. For instance, in the cases I have just related, where the dorsal portion was destroyed by thirds, the circulation was only stopped by the destruction of the whole of this portion of the medulla spinalis. Indeed, it was not entirely so, when this destruction, instead of being per- formed by tjiirds, was by fourths or by fifths. What could produce this strange difference? Repeated inquiries have suggested the follow- ing explanation. The destruction of any one portion of the spi- nal marrow, by producing death in all the parts which receive their nerves from it, considerably weakens the circulation in all those parts; but this weakness is not immediate; it only acquires its maximum a few minutes after. The circula- tion, which still continued with activity in a part of the neck after decapitation, becomes much weaker; therefore, when the cervical portion of the medulla spinalis has been destroyed, it de- creases also considerably in the shoulders, in the fore feet, and in a part of the thorax, when we pro- ceed to the destruction of the dorsal portion, at 120 EXPERIMENTS ON THE the three or four first vertebrae of the back, and so on. These successive destructions, though they do not produce the effect of a complete ligature of the arteries, nevertheless have the effect of an incomplete ligature. Now from all I have just stated upon the ligature of the arte- ries, connected with the destruction of the me- dulla spinalis, as the extent of the spinal marrow necessary to maintain the circulation is smaller in proportion as the circulation extends to fewer parts, it may be readily conceived that if, by the ligature of the vessels, or by amputation, the de- struction of a certain portion of the spinal mar- row is rendered practicable, without stopping the circulation, this operation, by weakening the circulation in all the parts corresponding with the portion thus destroyed, will render the destruction of another portion likewise possible. By the same mechanism, this renders the same operation practicable upon another portion, and so on, till, by these successive destructions, the portion of spinal marrow left untouched, can no longer be reduced, unless the circulation, thus gradually brought to the last degree of weak- ness, is entirely stopped. To this effect, produced PRINCIPLE OF LIFE. 121 by the partial destruction of the spinal marrow on the circulation in the corresponding parts, must be added another, analogous on the gene- ral circulation. It is, that the heart being more and more weakened by those destructions, the circulation is proportionably concentrated: it only preserves some degree of activity in the parts near the heart, and languishes in all those at a little distance. This explanation will elucidate many of the difficulties, to be met with in the experiments made on the medulla spinalis. Among these difficulties, those which embarrassed me the most were the differences, sometimes consider- able, which I have observed, when I wished to determine with precision, the exact length of spinal marrow necessary to the maintenance of circulation, for every age in every species. I pro- ceeded, as if groping in the dark. After having destroyed a certain length of the spinal marrow, whether respiration continued, or it was neces- sary to inflate the lungs, I waited some minutes to observe the effect of this injury. If the circu- Q 122 EXPERIMENTS ON THL lation was not stopped by it, I destroyed anothet portion; then again I waited a few minutes, to see the effect, and so on to the last partial destruc- tion, when the circulation appeared stopped. Then I considered the sum of all those succes- sive destructions, as the length of the medulla spinalis which must be destroyed, to stop the circulation in an animal of the species and age of that which had been the subject of the experi- ment. This effect was really produced, when such a length was destroyed at one operation. But when, instead of destroying it at once, or at four or five different times, I attempted to do it at two different operations, I was astonished to see the circulation stopped by the first, though the destruction of the medulla spinalis had not exceeded one half of the length, which Was thought necessary to produce that effect. And vice versa, when I had begun by a portion, the destruction of which had been found sufficient to stop the circulation, if by chance or design I happened to destroy afterwards the same portion at several times, I often found that the circula- tion was not stopped, unless I destroyed another portion, and that sometimes considerable. In a PRINCIPLE OF LIFE. 123 word, with each experiment there was a differ- ence in the result, and which, in most cases, was too striking to be considered as purely ac- cidental. After many fruitless efforts to elucidate this dark question, I determined to abandon it, not without regret at having sacrificed so many ani- mals, and lost so much time. I changed my plan, and, instead of trying to determine for each age the precise length of the medulla spinalis, the destruction of which stopped the circulation, my inquiries were confined to the effects of the three portions, the cervical, dorsal, and lumbar, when destroyed separately and at different ages. I have already given the results; they indicate only in a general manner, that the extent of spinal marrow, strictly required to maintain the circulation, is in proportion to the age of the animal. I no longer thought of the difficulties I had experienced, in the prosecution of my first plan, or rather I had lost all hopes of any elucidation, when I was led to study the effects of the ligature upon arteries, and to compare these effects with those produced by the de- 124 EXPERIMENTS ON THE struction of the spinal marrow. From that mo ment ah these difficulties vanished. Generally speaking, whenever the circulation has been much weakened by any cause, in a part somewhat important of the body, there is reason to believe that the general circulation will not be stopped, at least immediately, by the destruction of a like portion of medulla spinalis, which, if this circumstance had not taken place would have been sufficient to stop it. I will state an instance of it. I have sometimes ob- served that, by cutting through the spinal mar- row near the occiput, and then waiting several minutes, before I destroyed the cervical portion, this last operation did not stop the circulation even in rabbits of thirty days, in which it is always stopped, as we have seen above, when it is performed immediately. But it is easily known in these cases, that the circulation has been stopped, or considerably weakened in the head; by the gaping which continued at first, now ceasing, or becoming very rare and very weak; by the sensibility being extinguished in the eye and incapable of being excited; by the PRINCIPLE OF LIFE. 1^5 carotids being distended near the thorax, and easily changing colour; by the interruption or renewal of the inflation of the lungs, con- tracted and almost empty, and nearly of the same colour near the head. Nevertheless, these cases are very,rare, and it is correct to say, that the surest way to preserve life in rabbits of that age, after the destruction of the cervical portion of the medulla spinalis, is to begin by cutting off their heads. These facts, by showing that there is no por- tion of the medulla spinalis, which cannot be supplied by another, by means of certain ope- rations, prove in a satisfactory manner, that it is from every part of this spinal marrow, that the heart receives the principle of its power. We observe that the quantity, the contingent of power, which each portion of the spinal marrow furnishes to that organ, is at least equal to wha.fr it would stricdy require, to keep up the circula- tion, in the parts alone corresponding with that portion. Hence it might be inferred, that by cutting off portions of an animal at both ends, suitable ligatures being made on the blood-ves^ j25 EXPERIMENTS ON THE sels, the trunk might be so reduced, as always to admit the possibility of life's being maintained in it. I had no doubt of the correctness of this conclusion; strictly adhering to the method adopted in the prosecution of the inquiries, of drawing no conclusions but what appeared in- dubitably to flow from my experiment, and seeking afterwards by direct experiment, a con- firmation of those conclusions, I determined to know, whether it would be possible to keep up life in a simple stump of an animal. I was not entirely at liberty in the choice of this stump, because it was necessary that the heart and the lungs, should remain annexed to it, and in such a manner that the circulation and the inflation of the lungs, might be carried on without diffi- culty. These conditions can only be found in the breast. The thorax of a rabbit of thirty days, I accordingly proposed to keep alive after having separated it from the rest of the animal, by cutting off the anterior and posterior parts. My first essays were unsuccessful; I met with no difficulty in keeping up life after cutting off one of the two extremities of the animal, either the head or the hind part; but when PRINCIPLE OF LIFE. 127 I cut off both ends, and the breast was left alone, every sign of life was soon and irrevoca- bly extinguished. Eight times successively, did I fail in this experiment; I still persisted with unremitting perseverance, being fully persuaded of the possibility of success. What contributed to support my hope was, that by examining with attention all the circumstances of each ex- periment, I almost always discovered the cause of its failure. The three principal ones were, 1st. The passage of air into the blood vessels, a fatal accident, and unfortunately a very frequent one in experiments of this kind. 2d. The pas- sage of air into the cavity of the breast under the diaphragm, separated from the vertebral column. 3d. The decapitation being made too near the breast, which produced too copious a hemorrhage, especially through the vertebral arteries which cannot be tied, at the same time that it favoured much the passage of the air into the vessels. Finally, by varying the mode of operating, and by paying a much greater at- tention to every part of the experiment, my hope was completely realized; and I succeeded in maintaining life for upwards of three quarters 128 EXPERIMENTS ON THE of an hour, in the detached and isolated breast of a rabbit thirty days old. I have several times since obtained the same success. I have even obtained it by processes which had at first appeared to me unfavourable. Nevertheless, the following is that which has appeared to me to succeed the best. The belly of the animal is first opened; a liga- ture is passed round the aorta, immediately be- low the coeliac trunk, another is passed round the vena cava near the liver, a simple knot is tied in each of these ligatures, but is left somewhat toose. This being done, the trachea and bodi carotids are laid bare; each of these arteries is tied, conjointly with the external and internal jugular veins; the trachea is opened for the in- flation of the lungs; the spinal marrow is divided with a needle, near the occiput, and the inflation is begun, without waiting till the asphyxia has extinguished sensation; after it has been conti- nued for three or four minutes, the animal be- ing fully alive, the trachea is separated forward from the larynx, then the head is cut off with a pair of scissors, at the first vertebra? of the PRINCIPLE OF LIFE. 129 neck; and immediately resuming the inflation, which is to be continued for three or four mi- nutes; after which the knots are to be tightened which had been previously prepared upon the aorta and the inferior vena cava; the inflation is to be then renewed, and again interrupted at the end of three or four minutes, to cut off the hind part, which is performed by taking away the intestinal tube from the beginning of the duodenum, then by dividing with scissors the soft parts surrounding the vertebral column, and then the column itself, immediately below the ligatures made on the aorta and the vena cava. In this manner, there remains only the breast, the stomach, and the liver, which might also be removed if care be taken to prevent hemor- rhage. The operation being finished, all that remains is to continue the inflation of the lungs, as long as the breast shows any signs of life. The most apparent of those signs are the mo- tions and the sensation preserved in the fore feet, and the small writhing motions observed in the thorax, when the skin is severely pinched and when the posterior extremity of the dorsal portion of the medulla spinalis is touched. In R |3q EXPERIMENTS ON THE some cases, after carrying the experiment thus far I have destroyed the remainder of the cer- vical portion of the medulla spinalis and part of the dorsal; in those cases, although life only existed in the two posterior thirds of the breast, I could still prolong it. It is beyond a doubt, that if both the lungs and the heart could continue to perform their functions with any other portion, as they do with that of the breast, life might likewise be maintained in them. It is therefore demonstrated by a direct experiment, that the medulla spinalis of any portion whatever, may at once animate all the parts of that portion, and supply the heart with the power it requires to maintain the circula- tion in it; and that if life cannot be prolonged in any one portion taken at random, it is only be- cause the anatomical arrangement of the organs prevents it. But if the place of the heart could be supplied by injection—and if, for the regular continuance of this injection, there could be fur- nished a quantity of arterial blood, whether na- tural, or artificially formed, supposing such a formation possible,—then life might be indefi- PRINCIPLE OF LIFE. 131 nitely maintained in any portion; and conse- quently, after decapitation, even in the head itself, without destroying any of the functions peculiar to the brain. Not only life might thus be kept up both in the head and in any other por- tion separated from the body of an animal, but it might also be re-produced after its entire ex- tinction. It might be restored likewise to the whole body, and thereby a complete resurrec- tion be performed in the full extent of the word. But this requires some little explanation. From all I have stated in this work, life is produced by an impression of the arterial blood, made upon the brain and the medulla spinalis, or to a principle resulting from this impression. Therefore it is the cessation of this impression, the extinction of this principle, which constitutes death; and consequently to make life succeed death, or, in other words, to effect a resurrec- tion, it is necessary to renew this principle. Now, this renewal is impracticable; since, on the one hand, it cannot take place if the heart does not preserve sufficient power to propel the blood as far as the spinal marrow; and since, on the other, 132 EXPERIMENTS ON THE all the energy of this organ is dependent on this very principle, which by this hypothesis is supposed to be extinct. Therefore it is this re- ciprocity of action, now fully demonstrated, be- tween the heart and the medulla spinalis, which establishes the impossibility of resurrection in the actual state of things. But if there existed any means of supplying the natural circulation, which cannot be restored, it is certain that a dead body may be resuscitated sometime after death;—a time which would be limited by se- veral circumstances, and variable according to the species, the age of the animal, the causes of its death, the seasons, &c. The partial resur- rections which may be performed at pleasure, leave no doubt in that respect. Thus, if with this view you repeat an experiment stated above, which had already been made by Stenon, and which consists in tying the aorta opposite to the first lumbar vertebra, we have seen that a little while after sensation and motion have entirely dis- appeared in the hind part, yet the circulation and life have continued in the anterior part. But if, after waiting a time treble and even quadruple of that at the end of which all the signs of life have PRINCIPLE OF LIFE. 133 disappeared, you untie the aorta, sensation and motion return by degrees in the dead parts as cir- culation is re-established. In the same manner, by tying all the arteries that go to the head, you might reduce this part to a state of death; and all the intellectual functions peculiar to the animal which is the subject of the experi- ment would be not only weakened, disordered, or suspended, as in the case of asphyxia or syn- cope, but wholly annihilated, whilst the rest of the body would be full of life. These functions would be resumed afterwards, upon the arteries being untied. It is sufficiently evident, without my dwelling any longer upon this subject, why those partial resurrections are the only ones within the power of the physiologist, and at the same time the only ones he can admit in the common course of things. 134 EXPERIMENTS ON THE RECAPITULATORY OBSERVATIONS. I shall conclude by a recapitulation of the principal facts above stated. The principle of the sensation and motion of the trunk, has its seat in the medulla spinalis, and not in the brain; but the primum mobile of respiration resides in that part of the medulla oblongata which gives rise to the nerves of the eighth pair. From this double disposition, the section of the medulla spinalis near the occiput, and deca- pitation, annihilate the inspiratory motions, with- out causing a cessation of life in the trunk, which only dies by asphyxia and at the end of the same time as if respiration had been prevented in any other way, admitting that the hemorrhage had been stopped. In obviating asphyxia by the inflation of the lungs, the existence of an animal may be pro- PRINCIPLE OF LIFE. 13 5 traded for a time, the maximum of which in this case is the same as after the section of the nerves of the eighth pair. If, instead of being perfomed near the occiput, decapitation is performed upon the cranium, so as to spare the part in which the primum mobile of respiration resides, and to leave it in continu- ity with the spinal marrow, the animal may live and breathe by its own power, and without any assistance, until it dies of inanition. It is the max- imum of its existence in this other case; but, from well known causes, cold-blooded animals are the only ones that can reach it. Not only the life of the trunk is in general dependent upon the spinal marrow, but that of each part depends in a special manner upon the portion of the medulla from which it receives its serves; so that, by destroying a certain extent of the medulla spinalis, we only deprive those parts of life which receive their nerves from the me- dulla destroyed; all those which receive theirs from the medulla not destroyed, continue alive for a longer or a shorter time. 136 EXPERIMENTS ON THE If, instead of destroying the medulla, trans* verse sections be made, the parts which cor- respond to each segment of the medulla possess sensation and voluntary motion, but without any harmony, and in a manner as independent of one another as if the whole body of the animal had been cut transversely in the same places; in a word, there is, in this case, as many distinct centers of sensation as there have been seg- ments-cut in the medulla. That life may continue in any part of the body, besides the integrity of the corresponding me- dulla, the circulation constitutes an essential condition. If you interrupt the circulation in a part, death constantly follows; but even when this last effect is produced in the most unequi- vocal manner, life soon returns, if you can suc- ceed in restoring the circulation in this part, and particularly in the medulla spinalis. Death never happens, either in a part, or the whole body, as soon as the circulation has been interrupted, but only some time after. This time, which is determined in the animals of the PRINCIPLE OF LIFE. I37 same species and same age, is the longer in the warm-blooded as they are younger. Thus when the circulation is suddenly stopped in rabbits, whether by ligatures or by taking away the heart, sensation is only extinguished at the end of four- teen minutes, when they are new born; two mi- nutes and a half, when they are fifteen days old; and one minute, when they are thirty. In cold- blooded animals, it is only extinguished some hours after. The length of time which animals survive this experiment, so characterises the cessation of the circulation, that it is perfectly distinct from that which takes place in death from any other cause. For instance, it is always shorter in an animal, of whatever species or age, than when the death of the animal is occa- sioned by asphyxia. Since in every part of the body, life essen- tially depends upon the integrity of the corres- ponding spinal marrow, and the continuance of the circulation; and that, according to the Hal- Ierian theory of irritability, the motions of the heart, and consequently circulation, are inde- pendent of the nervous power; it would seem S 13 g EXPERIMENTS ON THE that we might at pleasure, continue the life of any one portion of an animal, after having pro- duced the death of all the other parts, b\ de- stroying the corresponding portion of spinal marrow: but this is not the case. After the de- struction of a certain extent of medulla spinalis, produced in any one part of the vetebral column, life only continues in the part the spinal marrow of which is left untouched a limited time, which is longer or shorter according to the age of the animal. Now, the duration of life in this case happens to be the same as if the heart had been removed from an animal of the same species and age. All the other phenomena which are then observed, such as the vacuity of the caro- tids, absence of the hemorrhage after the am. putation of the limbs, &c, concur to prove that the destruction of the medulla has instan- staneously deprived the heart of the energy necessary for maintaining the circulation, widi- out stopping at first its motions, which are no more than the motions of irritability. By assimilating these motions, without power, to those which take place during life, the an PRINCIPLE OF LIFE. 139 thors of the Hallerian school have fallen into error. In all species and at all ages the destruction of any one portion of the medulla spinalis, has always the effect of weakening the energy of the heart; but the portion which must be destroyed, to bring this weakness below the degree neces- sary for maintaining the circulation, varies in the different species, and is longer in the same species as the animal is younger. If ligatures be made either on the aorta or any other large arteries, previous to the destruc- tion of the medulla spinalis, the results are dif- ferent; and the destruction of the same portion of the spinal marrow, which, without these liga- tures, would have suddenly stopped the circu- lation, will be insufficient to produce this effect. Generally, by diminishing with ligatures the extent of the parts to which the heart is to dis- tribute blood, we lessen the degree of force which this organ requires to perform its func- tion, and we shorten in proportion the extent of 140 EXPERIMENTS ON THE the medulla, which is indispensable to maintain the circulation. The destruction of a portion of the spinal mar- row insufficient to stop the general circulation, always weakens it in the parts corresponding to the portion which has been destroyed, and, to a certain degree, acts as a ligature. Furthermore, the energy of the heart being weakened by this operation, the general circulation js concentrated, and only preserves some slight activity in the parts nearest to the heart, which likewise pro- duces a similar effect. Hence it happens, that when the spinal marrow is destroyed succesively in small portions, and at intervals, a much greater length may be destroyed without stop- ping the circulation, than would be sufficient to produce that effect, it it were destroyed at once. Whether by this method, or by ligatures made upon the arteries, there is no one portion of the medulla spinalis which cannot be pre- vented from co-operating in maintaining the cir- culation without destroying this function, there is none which may not become sufficient to PRINCIPLE OF LIFE. 141 maintain it; and we find that, at all ages, any one portion supplies the heart with a power sufficient to maintain the circulation in all the parts corresponding to that portion. Upon this is founded the possibility of preserving life in an isolated portion taken from the middle of an animal's body. But in whatever manner these experiments are conducted, whenever it is car- ried so far as to suppress the action of the spinal marrow, through its whole length, the circula- tion is irrevocably stopped. 142 EXPERIMENTS ON Tllk CONCLUSIONS. Among the numerous consequences flowing from these facts, I shall confine myself to stating the following: Life is produced by an impression of the ar- terial blood made upon the brain, and the me- dulla spinalis, or by a principle resulting from this impression. This impression being once produced, this principle once formed, has always a specific du- ration; but it is variable, according to the spe- cies and age of the animal. Consequently there is no one mean of killing an animal instantaneously, or rather there is no other mean than the simul- taneous destruction 'of the brain, and of all the medulla spinalis. The prolongation of life depends upon the continual renewal of this impression, nearly in the same manner as one body, moved by a first PRINCIPLE OF LIFE. j^n impulse, cannot continue to move indefinitely unless the same impulse is repeated at intervals. This property of the principle in question, namely, to survive wounds, and a very conside- rable destruction of the rest of the body, pro- vided its peculiar seat has not been injured, affords a ready criterion for determining in what part of the nervous power the primum mobile of such a function resides. For whenever by-de- stroying a certain portion either of the brain or of the spinal marrow, you cause the cessation of a function suddenly, and before the known period when it would cease naturally, you may be as- sured that this function depends upon the part that has been destroyed. It was in this manner that I discovered that the primum mobile of re- spiration had its seat in that part of the medulla oblongata which gives rise to the nerves of the eighth pair; and it is by pursuing this mode, that one might to a certain degree discover the use of certain parts of the brain, so much the object of speculation, but hitherto only defined in systems produced by a lively imagination. These in- quiries would be attended with so much the 144 EXPERIMENTS ON THE more success, as the animals might be selected of such ages and species, as are capable of sur- viving a longer time the cessation of the cir- culation. It is this impression, this principle formed in die brain and the spinal marrow, which, under the name of nervous power, and through the medium of the nerves, animates all the rest of the body, and presides over all its functions.* The heart derives all its powers from this principle, as do all the other parts the sensation and motion with which they are endowed, with this difference, that the heart derives its power from every point of the spinal marrow, without exception, whilst every part of the body is only animated by a portion of that medulla (by that which supplies its nerves); a difference which may serve to explain the intensity of the power of the heart, and its uninterrupted continuance, from the moment of conception, till the hour of death. PRINCIPLE OF LIFft. 145 The action of this principle upon the heart, and, consequently, the activity of the circula- tion, is not the same in all species; and, in the same species, it is more considerable in propor- tion as the animal is nearer the time of its birth; if we admit that it is so much greater, as a smaller portion of medulla spinalis is sufficient to maintain the circulation. This circumstance has many applications in physiology and patho* logy of the first period of life. From the great sympathetic nerve, the heart receives its principal nervous filaments; and it? is only through that nerve, that it can receive its energy from every point of the spinal marrow. The great sympathetic must, therefore, have its origin in this medulla; and thence the numerous questions that have been raised on the origin of this nerve, namely, whether it proceeds from the brain, or from the spinal marrow; or, as Bi- chat pretends, whether those different portions are only branches communicating from the gan- glions, which this author considers as so many smaller brains, forming a distinct nervous sys- tem, independent of the brain and the 9p«ufl T 146 EXPERIMENTS ON THE marrow (a). All these questions, hitherto inex- plicable in anatomy, are completely determined by experiments; and it is at the same time de- monstrated, that the ganglions cannot be con- sidered as smaller brains. From the same principle, we can no longer admit the assertion of Bichat, though pretty generally adopted, that there is in the same in- dividual two distinct lives, one animal, the other organic; that the brain is the only center of animal life; and that the heart, independent of the brain and of the nervous power, is the center of organic life. It must, however, be observed, that there is a real and a very important distinction to be made between the organs that receive their nerves from the great sympathetic, and those which receive theirs immediately from the medulla ob- (a) This opinion on the use of the ganglions appears to have been first produced by Winslow; and several authors, among others Winterl, Johnstone, Unzer, Le- cat, Pfeffinger, Prochaska, &c. had reproduced it before Bichat. PRINCIPLE OF LIFE. 147 longata and spinal marrow. The former receive their principle of action from the whole nervous power: their functions are not submitted to the will; they are exercised in every instant of life, and; at most, suffer only remissions. The latter, on the contrary, have their principle of action in a limited portion of the nervous power: their functions are submitted to the will; they are temporary, and can only be repeated after com- plete intermissions of longer or shorter duration. This distinction comprises nearly the same or- gans as that of the two lives; but it is evident that it rests upon a basis entirely different, since the organs of organic life, which, in the system of the two lives, is considered as independent of the brain and of the spinal marrow, are precisely those which receive the most powerful influence from it. Numerous anatomical, physiological, and pathological facts, can only be conceived and accounted for by this distinction. For in- stance, it is known that certain pains in the bowels cause debility, prostration of strength, and great disorder throughout the animal eco- nomy. This fact, which is unaccountable in the system of the two lives, is readily under- 14g EXPERIMENTS »N THE s$ood, from the moment we reflect that the in- testines derive their principle of action from all parts of the nervous power, through the great sympathetic, from which they receive their nerves; and that, consequently, their affections ought to re-act immediately upon every part of this same power. Peath fceing only the extinction of the prin- ciple formed in the brain and the spinal marrow by the action of arterial blood, it can only be partial when the extinction is so; it is general, when the extinction takes place through the the whole extent of the brain and the medulla spinalis,. Partial death, in any region it may happen, admits of a real resurrection, whenever the por- tion of medulla spinalis that has been left alive, can supply the heart with sufficient power to restore the circulation in the dead portion. If general death is irrevocable, it is not because the reproduction of the principle in question cannot be effected through the whole extent of the medulla spinalis, full as well as in a portion, PRINCIPLE OF LIEE. 149 at the end of a shorter or longer period after its entire extinction; but it is, because the heart, having lost all its power by the very effect of the extinction of this principle, without any means of recovering it, the circulation has ceased for ever. In short, the extinction of the principle of the medulla spinalis, and the spon- taneous cessation of the circulation, are two things inseparable and mutually announcing each other. Among the certain signs of death, we must therefore reckon all those which prove, that the circulation has ceased. For this reason the vacuity of the carotids is an infallible one, even when the contractions of the heart are still felt distinctly through the parietes of the thorax. Hence it follows that it is very far from being true, as has been asserted, that the last term of life extends to the abolition of irritability in this organ.* * Haller Elem. Physiolo. torn. VIII. lib. XXX. p. 12S. ISO EXPERIMENTS ON THE GENERAL RESULTS. Such are the principal results of a laborious investigation, in which I became insensibly en- gaged without foreseeing the consequent extent and difficulties. FronTmy first experiment, the sole object of which was to determine the time that a foetus can live without breathing, after the communication with the mother has ceased, to that where I succeeded in maintaining life in a portion extracted from the middle of the body of a rabbit, I have been irresistibly led from one experiment to another; the first experiment requiring a second to elucidate it, and this ano- ther, and so on successively. There are none which I have not repeated several times. In physiological inquiries, it becomes an indispen- sable necessity often to repeat and review the same experiment; a necessity which is grounded on the one hand upon the complication of the phenomena which they present, on the other on this, that many causes may produce their failure, and render the labours of this kind so long and PRINCIPLE OF LIFE. ^ 51 arduous. But of all those in which I engaged, there are none which I have repeated with more care, nor on which I have meditated longer, than those relative to the seat where the princi- ple of the power of the heart resided. Haller's theory, notwithstanding the imperfection im- puted to it, appeared to me still so well esta- blished, and all the modifications proposed ap- pearing unsatisfactory to me, that it was only from the maturest and the most attentive scru- tiny of the facts which overthrow its foundation that my conviction could be shaken. Although it is now full two years, since I discovered and intimated that the principle of the power of the heart resided in the spinal marrow, I now for the first time present the proofs to the public. I do not pretend, however, that Haller's theory is erroneous in all its parts. It is only so, when it deprives the nervous power of all active par- ticipation in the motions of the heart, which it exclusively ascribes to muscular irritability (a). (a) I ought to remark that under the name of Halle- mn theory, I do not only mean that, which this great 1^2 EXPERIMENTS ON THE But in other respects, as already stated in this work, I have had many opportunities of ascer- taining the truth of this other part of the same theory, that the blood, and the arterial blood particularly, is the stimulus, the presence of which determines the contractions Of the heart. man has consigned in his immortal work on physiology, Lib. iv. sect, v.; but also that of the authors of his school. It is worthy of remark, that Haller never did presume formally to deny the influence of the nervous power on the heart, and that he even seems to admit it, though indeed in a problematic manner, and inconsis- tently with the facts he brings forward to prove that these motions do not depend upon the brain. In short, he only appears to admit it as a conscientious obligation, if I may thus express myself, and because he could not otherwise dispose of the nerves of the heart. For which reason he has almost reduced it to nothing, in the last edition of the four first volumes of his physiology, (vide L'Auctarium,page 72, last paragraph, in which it is evi- dent we must read potest instead of nequit, page 73, Jine first.) The authors of his school have been much less re- served; they have maintained in formal terms, that the motions of the heart do in no way depend upon the nervous power. See among others, a dissertation of Fontana, page 234 of the third volume of the memoirs on the sensible and irritable parts of the animal body.— And the treatise on the poison of the viper, &c. Florence, 1781. torn. II. p. 169. 171. PRINCIPLE OF1 LIFE. 153 I have only treated in this work of the action of the medulla spinalis on the heart, it is not that the medulla oblongata does not exercise one also, but it is less considerable, and will engage my attention on a future occasion. U EXPERIMENTS ON THE SECTION III. Whe n it is once fully demonstrated that the life of the trunk has its principle in the spinal marrow, and that to protract it, it is only neces- sary to supply the want of natural respiration by the artificial inflation of the lungs, the first question which presents itself, is to determine how long it can be maintained by that process. It would seem that the best way of deciding this question, would be to try to maintain life the longest time possible in a certain number of individual animals. But if we should content our- selves with this process, which is purely empi- rical, we should only obtain an imperfect solu- tion. For the death of a decapitated animal may be produced or accelerated by several causes; some of which depend on the imperfection or failure of the means employed to maintain life; others on the accidents necessarily connected with so considerable and so serious a wound PRINCIPLE OF LIFE. 155 as that made by decapitation. Now, all these eauses are more or less foreign to the question, The particular object of inquiry, when our attention is directed to the time which an ani- mal can live after decapitation, is to ascertain how far the trunk can dispense with the action of the brain; or what amounts to the same thing, at what period and in what manner death occurs from the mere cessation of this action. It is therefore of this last and principal cause, that we must study the kind and the degree of influence, abstracted from every other. The brain can exercise no action upon the trunk but through the medium of the spinal marrow, and the nerves of the eighth pair (pneu- mo gastric); and it is evident that, after deca- pitation, this twofold mode of action is anni- hilated. We have seen that its want may be sup- plied, at least for some time, by the inflation of the lungs; but this inflation, in reality, acts only in place of the mechanical phenomena of respi- ration; and we have also seen that it is through the spinal marrow that the brain presides over 25Q EXPERIMENTS ON THE these phenomena. By inflating the lungs of « decapitated animal, therefore, we only obvia& the effects produced by the cessation of the in- fluence, which the brain exercised through the medium of the spinal marrow on respiration; ibut there is nothing to show that we remedy at the same time against the cessation of the in- fluence, exercised through the nerves of thf eighth pair, so as to enable us to prolong life indefinitely. To ascertain this, it was necessary to study the immediate effects of the cessation of this last kind of influence, considered by themselves and independent of any other connection, as they take place after the division or ligature of* the nerves of the eighth pair. Previous to this inr vestigation which now engages my attention, I had already had occasion, as I shall state by ant tyivovlo. atpin "hi vvv to ir&npx ovruvd'oln^tav, «AA« tiv^uf ctU6»Tty.a)v iritpvxoTot* zr*.r,o-ior a y°u add the effect of the recurrent nerves PRINCIPLE OP LIFE. 181 upon the glottis, and that of the par vagum upon the viscera of the thorax,—a double effect, always produced by dividing these nerves in the neck, then the dyspnoea is of the most violent kind; and there is no way of preventing threatened death, but by making an opening in the trachea. After it is made, respiration is per- formed without great efforts, though it is less frequent than in health, and it becomes so more and more. As often as you stop this opening with the finger, the animal falls into convulsions, as in the beginning of a complete asphyxia. It is exacdy so with rabbits and guinea-pigs; the dyspnoea, produced in them by the division of the recurrent, is less severe in proportion as they are older; but it is always greater in guinea- pigs than in rabbits. For instance, the latter are much less disordered by it when one month old, than the guinea-pigs at five months old. These may still die in consequence of it, in the space of twenty-four hours. The reason of these differences is easily con- ceived. It is produced by the opening of the 132 EXPERIMENTS ON THE glottis in animals of the same age, being, in pro- portion to the capacity of the lungs, larger in one species than in the other, and larger still in the adult than at the time of birth in those of the same species, as Professor Richerand had already ascertained in the human species (a). Now, if we admit that the figure of the glottis be nearly alike in these various animals, the areas of the like figures being to each other as the squares of similar dimensions, we find that a contraction of the same extent in the opening of the glottis, ought to intercept the passage of the air in very different degrees. This etiology of suffocation, produced by the division of the recurrent nerves, is in uniformity with that which I had published after my first experiments. It admits that the effect of this operation is to lessen the opening of the glottis. This appeared to me sufficiently proved by all the circumstances of suffocation, and particu- larly by the method which occasions its cessa- tion. But some respectable anatomists had (a) Nouveaux Elemensde Physiologie, 3d ed. Tom. II. p. 436. PRINCIPLE OF LIFE. 183 doubted it. Some asserted that the cartilages which compose the larynx, possess too little mobility in regard to each other, to allow any contraction worthy of notice, much less a de- gree sufficient to produce suffocation. Others said, that the property of the division of a nerve being to paralyze the parts to which this nerve is distributed, and the palsy being always ac- companied with relaxation, the section of the re- current nerves ought to relax, and consequently enlarge instead of contracting the glottis. To clear up these doubts, I performed the following experiments, before the society of Professors of the Faculty of Medicine of Paris. I took rabbits about two months old, in whom I separated the larynx from the os hyoides, and adjacent parts, without wounding either its own muscles or the recurrent nerves; after which I inclined it sufficiently towards the breast, to show plainly the opening of the glottis. This opening was evidently round, or at most slightly oval and perpendicular, (the larynx being sup- posed in its proper situation, and the animal on Ig^ EXPERIMENTS ON THE its feet) especially during the inspirations. This situation well ascertained, I divided the two nerves of the eighth pair at the middle of the neck; immediately the two arytenoid cartilages approached near to each other, and to the thy- roid; the opening of the glottis was diminished, and, instead of a hole nearly round, only pre- sented a permanent and perpendicular fissure. In other rabbits of the same age, the arytasnoid cartilages and the glottis, before the section of the same nerves, had motions corresponding with those of respiration. At each inspiration the glottis enlarged and assumed a round shape; afterwards, during the expiration, it grew nar- rower by the approximation of the arytenoid car- tilages to each other and towards the thyroid, and thus successively. But after the division both of the nerves of the eighth pair and the recurrents, it remained immoveable and con- tracted to a fissure. We are to observe, that these motions of the glottis only take place, or, at least, are only observable when respiration is somewhat laborious. When it is free, the glottis remains pretty widely open, with very litde variation. PRINCIPLE OF LIFE. 185 These comparative situations of the glottis, before and after the division of the nerves in question, in animals in whom this operation never causes threatened suffocation, even at the moment of their birth, sufficiently indicated what must take place in those upon whom it produces the effect. I have repeated this experiment which I had made upon rabbits, on three new born dogs and four cats. In these seven animals the opening of the larynx was attended by motions which had a regular correspondence with those of respiration. Upon each inspiration this open- ing enlarged itself, and towards the end of expi- ration it grew so narrow as to appear closed, and continued so till the moment when a new inspi- ration was begun. By cutting either the par va- gum or the recurrent on one side, the opening of the larynx lessened one half of its size imme- diately, and the arytaenoid cartilage of the same side was left motionless; that on the other side preserved its motions. WThen the two nerves of the eighth pair or both recurrents were divided, the two cartilages were motionless and contigu- ous on their internal edges; the ligaments of the glottis were also drawn together on their sharp 2 A 186 EXPERIMENTS ON THE edges, and the glottis appeared entirely closed. Every effort of inspiration made by the animals closed it more instead of opening it; and this was produced by the pressure of external air, which still increased the closure of those ligaments, on account of their oblique position, and the sort of cul-de-sac formed by their anterior surface. The expiration, on the contrary, was very easy. I wholly separated the larynx, together with a certain extent of the trachea, and introduced the end of a syringe into the latter: the air propelled by the syringe, issued freely through the larynx; but when the piston, drawn back in a contrary direction, inspired the air by the glottis, I felt, in moving it, a resistance equal to that I should have felt, if I had put my finger on the end of the syringe. Therefore, it is clearly and really, by paralys- ing the arytaenoid muscles, and thus relaxing tiie ligaments of the glottis, that the division of the recurrent nerves produces suffocation. From all I have just stated, it results that in experiments upon the division of the eighth PRINCIPLE OF LIFE. 187 pair, the effects of this operation upon the vis- cera of the thorax and abdomen, to which the nerves are distributed, are more or less com- plicated with the effect of the division of the recurrent nerves upon the larynx; and that according to the age and species of animals, this complication may be so great as to become the immediate cause of death, which in this case happens more or less suddenly, but long before the time when it would have taken place in consequence of the division of the eighth pair, free from this complication. These facts lead us therefore to a very simple explanation of those cases of sudden death, which happened after the division of the eighth pair; by which, as I have said above, some au- thors had been so much puzzled and others so gratified. In fact, of the authors whom I have mentioned as having observed those sudden deaths, those who have had the attention to point out the species and age of those animals on whom they made their experiments, inform us, they were dogs and cats, and that they were newly born. Igo EXPERIMENTS ON THE Here therefore appears a new effect of the di- vision of the recurrent nerves, and consequently of that of the par vagum, which I know not to have been observed by any of the numerous au- thors who have performed either of those two operations. It is known that Galen, to whom is ascribed, or rather who ascribed to himself, the discovery of the recurrent nerves, is also the first who has performed their division. The onlj! effect he observed from them was aphony: the animal on which he performed was judiciously selected to show this effect; it was a pig (a). This experiment was afterwards repeated by Vesalius (b). It was also by Colombus (c), by Riolan (d), by Bidloo (e), by Muralto (/), by Chirac (g), by Drelincourt (h), by George Martin (i), (a) De locis affectis. Lib. I. cap. 6. De praecognit. ad posthumum. p. 216. (b) De hum. corporis fabrica. Basileae. 1555. p. 823. (c) De re anatomica. Paribiis, 1562. p. 473 et477. (d) Encheiridium anatom. Parisiis, 1658. p. 243.— Opera an a to mi. p. 414. (e) Exercitationes anatom. chirurg. Lugd. Batav. 1708. p. 2. (/) (g) (*) (0 Cites par Hsdler, Elem. Phys. torn, III. p. 409. PR1NC1PLE OF LIPE. 189 by Courten (k), by Emmet (/). Portal (m), and Dupuytren (»X nave ^so performed it Aphony alone arrested the attention of all these authors, who confined themselves to the study- ing its various circumstances (o). Thus they examined how far the voice is weakened by the division of one nerve, how far it is extinguished by that of the two nerves, in what cases and how long before the animal can recover from it. All these questions being foreign to my object, I shall pay no attention to them. But I ought to caution my readers, when they peruse these au thors, to observe if the nerves have been tied or cut. The ligature may produce results that may (A) Experiments anatom. Ludg. Batav. 1681. p. 11. («) Essais et observ. de Medecine de la Societie d'Ed- imbourg. Paris, 1742. torn. II. p. i38. (m) Lettre de Collomb sur un coins de physiologic, fait par M. Portal en 1771. (n) Memoire cite plus haut. (o) The cause to which Martin ascribes aphony is re- markable. He thinks that the effect of the section of the recurrents is to enlarge the glottis. It was upon a pig, five or six weeks old, that he made his experiments. Since the operation, says he, the animal breathed as if the glot- tis had been too widely opened; he died at the end of six •r seven weeks, being still in a state of aphony. 190 EXPERIMENTS ON THE appear contradictory, as it has not been made tight enough wholly to intercept the action of the nervous power, or as it has been sufficiently so to produce that effect without disorganizing the nerve, or in short as it has been so far so as to disorganize it. In the first case, aphony is more or less incomplete, in whatever degree it may exist; in the second, it ceases as soon as the li- gature is removed; it continues in the third, after the removal of the ligatures, as if the nerves had been divided. This remark is applicable to the ligature of the par vagum, and to that of the other nerves. Though the effects of the liga- ture, when carried to the degree which conr stitutes the two last cases just mentioned, be nearly the same with those of the division, ne- vertheless, to avoid all doubt, I have always had recourse to the division in my experiments either on the recurrent or the par vagum. But the authors I have quoted, have indis- criminately employed both. the ligature and the division; and if, on reciting their experi- ments, I have mentioned most commonly the PRINCIPLE OF LIFE. 191 division, it was with a view to avoid unneces- sary details. From all that precedes, it results that to esti- mate correctly the effects of the division of the par vagum upon the viscera of the thorax, it is necessary first to know those of the division of the recurrents; and that in most cases, it is proper to begin destroying the effects of the latter, by making a large opening in the trachea, taking away the piece. Not that this open- ing is free from inconvenience; it occasions in- flammation, and consequent swelling in the sur- rounding parts, especially in the membrane that lines the trachea; extraneous bodies may also be introduced into it; finally, the muscles and the skin often obstruct it. But I know of no other means that can supply the want of this opening. All that can be done, in cases where the inconveniences cannot be prevented, is to account for them in the result. Let us suppose then, that by performing the division of the par vagum, we have ascer- tained, that no effect capable of affecting respi- 192 EXPERIMENTS ON THE ration shall be produced upon die larynx; the question is to seek in this case, what is the cause of death. I have said before, that, in this experiment, I had no other object in view at first, than to know if the periods at which the animals of different ages die, accorded with the lapse of time in which animals of the same species and the same age perish by asphyxia. The comparison was easy to be made; for the lapse of time in which animals may support asphyxia, though variable according to the age, is nearly fixed for every age, and only admits a very small latitude in individuals of the same species. I therefore performed the division of the eighth pair upon different species of animals, and particularly upon rabbits, from the moment of their birth, to the age of one or two months. I found nothing certain nor settled, in the time in which animals of the same age perished in consequence of it; and I remarked, in the differ- ent ages, nothing to be compared to this de- creasing law, according to which animals bear a shorter asphyxia, in proportion as they arc older. Thus I have seen new born rabbits, &c. die after the division of the par vagum, full as PRINCIPLE OF LIFE. 193 quickly as others aged two months; and fre- quently the latter survive as long as those much younger. This led me to think that they do not die of asphyxia, or that if they do, it is compli- cated by some circumstances, variable accord- ing to the individuals. This was the opinion I had adopted, when my experiments upon deca- pitation brought me back to resume those on the division of the eighth pair; with a view to discover, if possible, what was the true, or, at least, the principal cause of death. I shall not here state minutely all the pheno- mena produced by these operations; they have been observed and described by the authors above mentioned. I am only to attend to the results. Therefore when we examine these phe- nomena with attention, we find that the gastric viscera, the lungs and the heart are affected. The gastric viscera, because the animals are more or less distressed with nausea and even with vomitings, in the species capable of vomit- ing;—the lungs, because there is always a con- siderable dyspnoea, the intensity of which only 2B 194 EXPERIMENTS ON THE increases till death;-—the heart, because in ge- neral the carotids lose their fulness and tension. The heart, the lungs, and the stomach are organs of so great importance, and the disorder of their functions so far exposes the existence of the animal, that one alone would be sufficient to cause death. It is possible, therefore, that each of those organs, considered separately, should he so violently affected by die division of the nerves of the par vagum as to occasion it; and I will say, that this appears to me very probable. Never- theless it cannot be thence concluded that the immediate cause of death resides in all and in each of these organs. For, on the one hand, they may not be affected in the same degree; and on the other, admitting that they should be, their functions, though indispensable to the support of life, are so in a manner more or less imme- diate; I mean that the cessation of the functions of each of those organs, though necessarily mor- tal, is not so in the same time; and that conse- quently the disorder of one organ causing death before that of another has had time to produce the same effect, it is only to the first that this effect must be attributed. Let us suppose, for PRINCIPLE OF LIFE. 195 instance, that in an adult rabbit the functions of the heart, of the lungs, and of the stomach cease entirely, and at the same time; in this case death will be almost sudden, and it will take place pre- cisely within the same time as if the functions of the heart had ceased. It is evident that we shall not be able to ascribe it to the cessation of the functions of the stomach, since an adult rab- bit only dies after three weeks complete absti- nence; nor to that of the functions of the lungs, for although the length of time during which rabbits outlive it, is very short, it is at least twice as long as that which they outlive the ces- sation of circulation. If, on the contrary, the functions of die heart should continue undimi- nished, and those of the lungs and stomach were alone annihilated, death in this case would also be very prompt, but less so than in the first case; it would happen in the same space of time as after a complete asphyxia, nor could we attribute to it the cessation of the functions of the stomach. If the disorder of those organs was proportionably more violent in one than in the other, and that in neither of them was it sufficient wholly to suspend their functions, the effects would no longer be the same, and death would no longer 196 EXPERIMENTS ON THE be attributed to that organ, the functions of which admit the shortest interruption; but it would depend upon the organ, the disorder of which would be the most considerable; or rather the cause of death would be in a compound ratio of the disorder of the organ and the importance of its functions. This is what takes place after the division of the nerves of the par vagum. In this experiment the heart, the lungs, and the stomach, are affected in different degrees, and none of these organs are sufficiently so as entirely to suspend its functions, except the stomach in certain cases. To inquire how the division of those nerves occasions death in animals, is there- fore to inquire which among the impaired func- tions are those which are sufficiently so as to produce death before the disorder of the others has had time to produce the same effect. The (principal sign by which the heart is known to be disordered after the division of the par vagum is, as I have said before, a decrease of the fulness and tension of the arterial system, which is very easily distinguished in the carotids. It is very probable, that the motions of this organ also suffer disorders, both as to their frequency PRINCIPLE OF LIFE. 197 and regularity, but it is difficult to ascertain it, and not to confound the confusion caused by pain and fear, during the experiment, which is renewed by the agitation excited whenever the hand is laid upon the breast of the animal to feel the motions of the heart, with that which is only owing to the section of the nerves. Notwith- standing I have never observed that those dis- orders were as considerable as Willis and Lower have said, at least in the beginning of the ex- periment. Towards the end, when death is near, the pulsations of the heart are very unfrequent, and irregular, but many causes may contribute to make them so. In short, the disorder of the heart would, no doubt, in time produce unfa- vourable effects, and it ought to aggravate the other symptoms, but nothing shows that they may be considered as the immediate cause of death. I shall endeavour in another instance to determine, by direct experiments, the kind of influence the brain exercises upon circulation through the intermedium of the par vagum. The disorder of the stomach is, in general, much more severe than that of the heart; for the 193 EXPERIMENTS ON THE functions of the former of these organs suffer a much greater disorder than those of the latter. I even think that in certain cases, of all the func* tions injured by the division of the par vagum, those of the stomach are so in the highest de- gree. At least, this is what takes place in some species. In guinea-pigs, for instance, digestion appears to be not only weakened or deranged, but entirely abolished. I had divided the par vagum on the right side, in a female guinea-pig about eighteen months old. Respiration still continuing pretty free, and the anxiety being moderate, die animal continued to eat. But in proportion as it eat its belly increased in size. It became so enlarged, that its size was almost equal to the length of its body. It died in four days and four hours after the division of the nerves. The stomach occupied almost all the capacity of the belly, it was distended by a large quantity of food, which was found nearly in the same state as that in which it had been swallowed. It is evident that in this experiment, the sto- mach had wholly lost its power of digesting and PRINCIPLE OF LIFE. 199 that of propelling the food into the intestines. This effect does not always take place after the division of one single nerve, but we can scarcely doubt that the division of both nerves will ever produce it, especially when we consider in this last case, how guinea-pigs are distressed by nausea and efforts to vomit. Now, after the division of the two nerves, guinea-pigs of the age of that we allude to, die in the space of three or four hours, and sometimes still sooner. Their death cannot therefore be ascribed to the abolition of the digestive power* which they are able to survive upwards of four days, even when it is most complete. I say upwards of four day*; for it appears that in the case I have just mentioned, the abolition of the digestive power was the occasional cause of death, and that the proximate cause, was the result of the enor- mous distensions of the stomach, which had rendered respiration very laborious, and had, besides, determined a certain state of phlogosis. in the membranes of this viscus, as well as in the omentum and the peritonaeum. It is highly presumable, that had it not been for this com- plication, the animal would have lived the same 200 EXPERIMENTS ON THE length of time, as during a complete abstinence of nine or ten days. As death cannot be attributed to the state of the stomach, even in animals, the digestion of which is destroyed, much less can it be so in those with which, like the rabbits, the gastric symptoms are less violent. I shall add that I have never met with that corruption, that putrid degeneracy of aliments, contained in the sto- mach, which several respectable authors have considered as the cause of death. I had expect- ed, that this effect would be more observable and easy to distinguish in animals still sucking; and by dividing the par vagum at different ages, I had bestowed particular attention on those which took no other food than the mother's milk. But on examining compara- tively with this view, animals who had died of this operation, and those who died in any other manner, the milk contained in the stomach of both, ever presented the same appearance. Be- sides, admitting that the aliments are corrupted in the stomach of animals, in whom we had divided the eighth pair, could it be thence con- PRINCIPLE OF LIFE. 201 eluded, that this corruption is the immediate cause of so quick a death, as that which most frequently takes place in this experiment? Is it not known, that in certain disorders of the sto- mach, the aliments undergo a variety of very considerable alterations, which do not prevent the individuals labouring under those disorders, from prolonging their life for a sufficient time? Finally, I shall add that the stomach itself, if I except a slight phlogosis, has presented to my view nothing particular, and this state was only observable in a small number of cases. Of all the symptoms produced by the division of the par vagum, those in which respiration is concerned, are at once the most steady and the most remarkable; for this reason, they have been observed by most authors who have repeated this experiment. These symptoms manifest them- selves as soon as the nerves have been divided, and their severity increases more and more. Thus, respiration is slow, and performed principally by the elevation of the first ribs, and in proportion as it becomes more laborious, every inspiratory power is called into action. The animal keeps 2C 202 EXPERIMENTS ON THE itself quiet, (especially rabbits and guinea-pigs,) and seems only desirous of inspiring as much air as it can. The colour of the arterial blood at first but litde changed, loses its brightness by degrees, and assumes darker shades. The animal is found by the touch to become colder. Nevertheless, respiration is never wholly stopped immediately after the division of the nerves, as digestion ap- pears to be, at least in certain cases; and it is scarcely to be doubted, that if the dyspnoea made no progress, and continued such as it is in the be- ginning of the experiment, the animal could live a considerable time, and would die of inanition rather than of asphyxia. If the immediate cause of death resides in the lungs, this cause should possess the property of acquiring gradually, such an intensity, as to render respiration more laborious, and to produce complete asphyxia in the end. Therefore, in all the animals that have died of the division of the par vagum, we constantly find that the lungs are more voluminous than in the natural state, and that they are gorged with blood. The sanguine in- gorgement gives them a brown and red colour, which is not commonly uniform, but which is PRINCIPLE OF LIPS. 203 spread in large spaces. The pulmonary vesicula are so depressed by it, that if you separate those spaces from the portions which are left more or less free from it, and throw them into water, they sink to the bottom. Further, we most frequentiy meet in the bronchia;, with a frothy fluid, sometimes of a reddish colour, in sufficient quantity to fill up the pulmonary vesi- culas, and the greatest part of the bronchia?, which swells the lungs in the spaces which are not gorged with blood. This fluid is produced by a serous extravasation which is formed in the aerial tubes, and which are converted into froth by the respiratory motions, by mixing it with the inspired air. This fluid is found in great quantity in rabbits and guinea-pigs; it is often seen to issue out of their mouth and nostrils in the last moments of life. After death it flows through the incisions made in the lungs; and it is often sufficient to make an opening in the trachea, and to compress the belly and the breast, to make it flow through this opening. The effect of the sanguine engorgement and frothy effusion, is evidently to prevent the air from penetrating into the pulmonary vesicul*; 204 EXPERIMENTS ON THE and the inspection of these two states of the lungs, leaves no doubt that if they should occur immediately after the division of the par vagum, in the degree observed after death, the asphyxia would be complete from the very first instant. But they are only formed and increased gra- dually, as it is easy to ascertain by killing ani- mals at different periods after the division of the par vagum, to examine their lungs. The engorgement of blood, and the frothy effusion, are somewhat in an inverse ratio of one to the other. When the effusion happens early, it suffocates the animal before the engorgement has had time to make much progress, and death happens sooner. When, on the contrary, this effusion is formed slowly, and in a small quan- tity, the animal dies later, and only when its lungs are almost entirely gorged with blood. The time which both of these states of the lungs takes for their formation, is very variable, and appears to belong to individual circumstances, rather than to the age of animals of the same species; hence the time which the animals sur- vive this experiment ought to vary in the same PRINCIPLE OF LIFE. 205 way; and it does in fact vary much, as I have said before. This explains the reason why this time does not accord with that during which animals of the same species and age may sup- port sudden and complete asphyxia. It remains to inquire in what way the division of the par vagum produces both these effects in the lungs. It is probable that it is in a manner analogous to what takes place in the other parts, the nerves of which are divided. It is known that they fall into a state of palsy and flaccidity, not much unlike what takes place after death. Without doubt there also happens in the lungs a loss of tone, a sort of palsy. At least this is what appears to indicate the remarkable weakness observed in the texture of this viscus, which is easily torn, especially in the places which are gorged with blood. The experiment of Hales confirms this opinion. This author (a) found that by introducing blood into the pulmonary artery, through a tube adapted to this artery, (a) Hacmastatique sauvages translation. Geneva 1744, eleventh experiment, p. 61-6. 206 EXPERIMENTS ON THE held vertically and only two feet high, the lungs were distended and become very red, and that serosity is poured into the pulmonary vesiculae through the arterial coats. Hales observes, with reason, that this ready transudation of the se- rosity is caused by the relaxation and atony that exist after death. It has been seen that among the authors who were engaged in the division of the nerves of the eighth pair, several had perceived the san- guine engorgement of the lungs, and that some had even indicated it as a cause of death; but at the time when these latter authors wrote, the true theory of respiration was not yet known; it was not to asphyxia they had referred this cause, but to a hemorrhage, or a pulmonary inflammation carried to a mortal degree. As to the effusion of a fluid into the branchiae, I do not know that any other, besides Mr. Blainville, has made men- tion of it; and it is recollected that this learned man had not thoroughly investigated its effects on respiration, any more than those of the san- guine engorgement of the lungs-. PRINCIPLE OP LIFE. 207 In a memoir which I had the honour of pre- senting to the first class of the Institute in the year 1809, on the experiment in question, I ascribed the death of animals to the closure of the glottis; or, when the glottis remained suffi- ciently open, to the two states of the lungs just mentioned; the class appointed a committee to examine the facts. I shall here produce the re- sults of the experiments which I then repeated before the commissaries, and which Messrs. Dumeril and Blainville were good enough to attend. To shorten this account I shall only re- late the experiments upon the par vagum, and must omit those which I made at the same time on the recurrent nerves. The division of the eighth pair of nerves was performed upon a dog fifteen days old. Respira- tion immediately became very laborious. The animal opened its mouth very wide, and made great motions of the thorax for respiration. The carotids being uncovered were of a brown colour. At the expiration of five minutes, the body hav- ing lost its vigour and the head being in a droop- ing posture, a large opening was made in the 208 EXPERIMENTS ON THE trachea: respiration soon ceased to be laborious; the carotids assumed a beautiful purple colour, and the strength returned. This fact, which argues against the mode of asphyxia adopted by Dupuytren, proves at the same time against Dumas's opinion, that air can penetrate into the lungs freely enough, and without the help of inflation during the first moments of the experiment. The same nerves were divided in two guinea- pigs about a year old, and in three rabbits about two months old. A fourth rabbit of the same breed, was strangled by means of a tight ligature round the trachea, with a view of com- paring its lungs with those of the three others. Having terminated these experiments, the animals were placed in a lower room, and re- mained there for twenty-four hours, when we examined the bodies. We expected to find them all dead by that time; and they were so in fact. PRINCIPLE OF LIFE. 209 The lungs of the dog were very red and filled with blood, but less so than they are commonly found in this experiment No portion of them sunk to the bottom in water. The cold of a low and damp room ought to have contributed to destroy this little animal, which was yet accus- tomed to the heat of its mother, before the di- vision of the par vagum had been performed long enough to produce its entire effect upon the lungs. For cold alone is sufficient to kill very young animals in a very short time. In the lungs of the two guinea-pigs, an en- gorgement of blood was observed very dis- tinctly, and distributed in large spots. The bronchia? of one of these animals, was filled up with a reddish and frothy fluid. Those of the other only contained a very small quantity. A fluid entirely similar was abundantly found in the bronchiae of one of the three rabbits; a slight pressure upon the abdomen and thorax was sufficient to make it flow out, by an opening made in the trachea. One of the two others pre- sented only a small quantity of this fluid. The 2D 210 EXPERIMENTS ON THE third appeared not to contain any. But in this last animal, we found a serous effusion and some hydatids in the two cavities of the thorax. In these three animals, the lungs were swelled with blood, and of a brownish red colour in some places, between which smaller ones had preserved the natural pale rose colour of the lungs. On separating and throwing into water the engorged masses, they sunk to the bottom. Nothing similar was observed in the rabbit that had been strangled. Its lungs were filled with air throughout, and of an uniform pale rose colour; they were likewise flaccid and had diminished in bulk, while the lungs of the other three, as well as those of the dog and the two guinea-pigs, were more or less tumid. I must here remark in respect to the sanguine engorgement of the lungs, that it is not only after the division of the par vagum that it is met with; it is also observed in several other cases, and principally in the most of those, whose death has been the result of a long continued asphyxia. But in all these cases, it does not present' precisely the same appearances and the PRINCIPLE OF LIFE. 211 lungs are not tumified in the same manner, as after the division of the eighth pair. The effu- sion of a serous fluid in the bronchiae, is also observed in other cases. It comes on more par- ticulary in the affections of the chest, compli- cated with debility and atony, and is the most frequent termination of peripneumonia notha, which is so often fatal to old people. Their bronchiae fills up progressively, the rattle comes on, and they die stifled (a). Let us recapitulate the principle facts, rela- tive to the division of the par vagum. It most commonly occurs, that the division of a single nerve is not mortal. That of the two nerves is constantiy so. The division of the two nerves affects at the same time the larynx, the heart, the alimentary canal and the lungs. The affection of the larynx is propagated by the recurrent nerves, in such a manner as that the division of the nerves is (a) Cull en's Practice. 212 EXPERIMENTS ON THE sufficient to produce it. This affection consists not only in an alteration of the voice, but also in a diminution of the aperture of the glottis. Both of these effects are owing to the paralysis of the arytaenoid muscles, which permit the arytaenoid cartilages to incline towards the glot- tis, which relaxes its ligaments, and brings them nearer to one another at the same time; and all these parts remain motionless in that state. The diminution of the aperture of the glottis, varies according to the. species, and still more so, according to the age. In certain species, such as dogs, and especially cats, it is so consi- derable, that those animals are strangled nearly as r* adily as if the trachea had been tied. As these animals grow up the danger diminishes; and when they have attained a certain age they are but slightly affected by it; at least, this is what happens in dogs. Hence, we may conclude, that of all the symptoms produced by the division of the par vagum, the most severe, and those which cause death most prompdy, are in certain cases those PRINCIPLE OF LIFE. 213 which are connected with the larynx. In gene- ral, whenever the difficulty of breathing increases immediately after the operation, it is to be pre- sumed, that its principal cause exists in the larynx. For example, the violence with which dyspnoea makes its sudden appearance in horses even of an adult age, and the quickness of their death, proves that, in those animals, the glottis undergoes a considerable contraction. A large opening made in the trachea, furnishes at once the remedy and etiology of all those cases. The aperture of the glottis is, therefore, never in the living animal such as we find it in the dead body; and the arytaenoid cartilages require to be supported by their muscles, as the superior eye-lid requires to be supported by its own muscle. The affection of the heart is difficult to be determined; but whatever may be the effects it can finally produce, it does not prevent the con- tinuing of the circulation; and other functions are disordered in a mortal degree, before these effects have acquired all their force. 214 EXPERIMENTS ON THE The affection of the stomach is in general more violent. It is so in different degrees ac- cording to the species, and even according to the individuals of the same species. But we do not find in this viscus any morbid state well determined, except sometimes a slight state of phlogosis. It does not appear that the aliments contained in it, undergo any particular putre- faction; and even if this should take place, it is very doubtful whether this corruption, any more than the entire destruction of the func- tions of the stomach, would be the immediate cause of death. Finally, death comes on at a period, and with such a series of symptoms, as does not permit us to place its cause in the stomach. These symptoms are those which depend upon an affection of the lungs; they are the most remarkable and the most constant which we ob- serve in the experiment in question. Respira- tion is deep and laborious, and becomes so more and more. It sometimes takes place with a frothy noise, which can be heard in the thorax. The arterial blood assumes a darker hue and PRINCIPLE OF LIFE. 215 the animal loses its heat. After death we find the lungs swelled with air, partly filled with blood and partly with a serous and often frothy fluid, and inspection of them clearly shows that the exterior air could no more penetrate, or if it did, it was in a very small quantity. The forma- tion, not sudden, but progressive, and more or less rapid, of the sanguine engorgement, and of the serous effusion in the lungs, accounts for the ever increasing progress of dyspnoea. From all these facts, we may conclude that the division of the nerves of the par vagum kills animals by producing asphyxia, and that as- phyxia may take place in three different man- ners: 1. By the diminution of the aperture of the glottis. 2. By the sanguine engorgement of the lungs. 3. By the effusion of a serous fluid in the bronchiae. According to the species, age, and constitution of the animals, death may be occasioned by one alone of these three modes of asphyxia, or by two, or even by varied com- binations of the three. 216 EXPERIMENTS ON THE Such is the most satisfactory solution that I could obtain, of one of the questions that I had proposed to myself in the beginning of this memoir, viz. What is the cause of death, after the division of the par vagum? As to this other question, How long can animals survive it? the same solution indicates that this time cannot be always the same, because the causes producing asphyxia attain their maximum only in a variable manner, and which the most often depends upon circumstances entirely relating to the individual. In fact, out of thirty-one rabbits from one to forty days, upon whom I divided the par vagum, death occurred between six hours and a quarter and eighteen hours and a half. To apply these results to decapitated animals, it became necessary to ascertain whether the time during which life can be maintained in these animals, and whether the state of their lungs after death, bear any relation with what is observed after the division of the par va&um. This is the question which I proposed. Nor is it an easy one to resolve. The reason of it is, that even when decapitation has been performed in PRINCIPLE OF LIFE. 217 the most successful manner, and when every thing announces that the experiment will be at- tended with most success; pulmonary inflation being long protracted, produces, in a great num- ber of cases, accidents, which become mortal long before the period when these animals would have perished merely by the cessation of the influence of the brain. The most frequent of these are the passage of inflated air into the blood- vessels of the lungs, and the passage of the same air in the substance of the lungs, or into the cavity of the thorax and into that of the abdomen. The first of these circumstances kills the ani- mals by preventing circulation; the others de- stroy the effect of pulmonary inflation, and in- crease the difficulty to such a degree that it soon becomes impossible to be continued. It is some- times only at the expiration of two or three hours of inflation that either of these accidents takes place. Hence it is a very tedious, and even disgusting circumstance, to be obliged to recom- mence so often experiments of such length, to be able to conduct some of them to a happy issue, in such a manner that the animal should die without his death being produced by any 2E 218 EXPERIMENTS ON THE accident or any other circumstance, except by the cessation of the influence of the brain. The longest space of time during which I have been able to maintain life in decapitated rabbits, was from five hours to five and a half; and even m this I could only succeed three times. It was in summer, the temperature of the atmosphere be- ing at twenty-five degrees (centigrade ther- mometer.) The rabbits were twelve days old. It appears to me that the space of time during which I have been able to maintain life in them is nearly the same, as the shortest period in which the individuals of the same species survive after the division of the par vagum, and which is, as I have already mentioned, six hours and a quar- ter, to leave no doubt that life may be maintained as long, and even longer in rabbits after decapi- tation, if this operation did not place them in a situation much more critical than the simple di- vision of the par vagum. But besides the he- morrhage more or less copious, which always takes place, the cutting instrument carried into the seat of the nervous power produces a commotion which they sometimes have a great difficulty to recover from, and which weakens PRINCIPLE OF LIFE. 219 all their functions. It results from this, that, in general, they are in a state of atony very dis- cernable (a). This state of atony is equally re- markable in the lungs, by the ease and quickness with which the serous effusion which I have mentioned is formed. When life has been sup- ported during a certain time in a decapitated rabbit, his lungs are always found swelled and filled with a frothy fluid. I have sometimes seen the effusion of this fluid carried to such a degree as to render inflation impossible in less than an hour. It comes on more rapidly after the divi- sion of the par vagum, and I have always con- sidered it as the principal cause of death, when- ever it did not depend upon some manifest accident. There is also formed in the lungs a sanguine engorgement characterised by spots of a brownish red colour, and which is more con- siderable in proportion as life has been supported (a) This commotion also takes place in reptiles. It has been remarked very often, that salamanders, as soon as they have been decapitated, are in a state of torpor and stupor which has the appearance of threatening death. Yet they recover, by degrees, well enough to live whole months after. 220 EXPERIMENTS ON THE for a longer space of time, and as the serous effu- sion has been formed less rapidly. The rabbits kept alive after decapitation, therefore, have their lungs apparendy in the same state, as after the division of the nerves of the eighth pair; and consequently whatever may be done to protract their existence, they must perish of asphyxia as in this last case, and at the furthest in the same time. This is the maximum of their existence, but in a great many cases it is not possible to make them reach it; for which I have given sufficient reasons (a). (a) There is a reason with which I was not acquaint- ed, when I was employed in these researches. I sup- posed that pulmonary inflation might completely supply the place of natural respiration. But I have since found, and I have proved in a memoir, which I had the honour of recently presenting to the first class of the Institute, that it supplies the place of that function very imper- fectly. In fact, if in a rabbit, sound and healthy in other respects, we substitute pulmonary inflation to natural respiration, and that no other passage for air into the lungs, except that through the syringe, should be left open, the animal becomes almost as cold as if he were dead; and by continuing this operation for a certain time, PRINCIPLE OF LIFE, 221 I have only considered the questions which have been discussed throughout this work physiologically; but applications to pathology are obvious. I shall confine myself to point- ing out some of them. There are many observations, of destructions of considerable portions of the brain, which have been attended with death only after a certain space of time. Thus, we have often seen, either in battle or in cases of suicide, balls go through the brain, and notwithstanding, the patients have we may actually make him perish by cold. I was far from suspecting that pulmonary inflation, by the aid of which we produce such surprising effects, could be at- tended with such serious inconveniences. Now, since notwithstanding these inconveniences, I have supported life during five hours and a half in decapitated rabbits, we may easily conceive that if they had not taken place, the animals might have been kept alive during a much longer space of time, but notwithstanding, never beyond the time they live after the division of the eighth pair. It appears that inflation contributes to produce, or at least to accelerate that frothy effusion, which in gene- ral we find more frequently and more abundantly after decapitation, than after the division of the eighth pair. For very often a similar one is formed in the sound animals which we inflate. 222 EXPERIMENTS ON THE survived some time. In sanguine apoplexy, it frequently happens that life is prolonged for a considerable time after the blood effused in the substance of the brain has destroyed the intel- lectual functions, and the greatest part of the senses. In all these cases, whatever may be the disorganization existing in the brain,, life continues, as long as this disorganization does not extend to that spot of the medulla oblongata which gives rise to the nerves of the eighth pair. On the contrary, whenever by any exterior or interior cause, this same part is all at once de- stroyed, or affected in such a manner as to pre- vent the exercise of its functions, respiration is stopped at the very instant, and the patient dies as quickly as if he had been strangled. Death may even appear to have been instanstaneous, owing to the torpor and stupor which are sud- denly added to asphyxia, and which are the effects of the commotion which the affection of the brain produces in the nervous power. When the origin of the nerves of the eighth pair is affected in a manner somewhat less serious, and its functions are not suspended but PRINCIPLE OF LIFE. 22$ only altered, symptoms appear very similar to those which take place after the divison of the , eighth pair. This is what is observed in a great many cases of apoplexy, which begin with ob- stinate vomitings, and which, on that account, might be taken for an indigestion. At the same time, there is a difficulty in respiration, the voice is altered or even more or less difficult. These symptoms indicate a mortal apoplexy when they precede or accompany the other signs of the dis- ease. Sometimes before the apoplectic fit, the pa- tients have been subject at several different times to obstinate coughs, which assumed the appear- ance of catarrhal affections. But it may happen, especially in childhood, where sanguine affec- tions in the brain are rare, that the cause which acts upon the medulla oblongata is easier to be removed, and, for instance, it is produced by an engorgement of the vessels of that part. In this case, whatever may be the violence of the symp- toms just mentioned, they will admit of a pretty speedy cure. Instances of this case are not rare. I have recently seen a remarkable case in a child of eight years old, a daughter of Mr. Benizy, engraver, rue de Harlay, number twenty-one. 224 EXPERIMENTS ON THE This child had, for about fifteen days, laboured under a severe cough, when one morning, after a light breakfast, she was attacked with con- siderable vomiting, which lasted upwards of two- hours. At the same time her respiration became difficult, her voice became weak, and entirely died away; finally she fainted. I saw her three hours after the attack of vomiting. She had done vomiting, but was still senseless, could not ar- ticulate a word, her respiration continued to be laborious, there was froth at the nostrils; the eyes were fixed, and nearly insensible; the jaws not fixed; and deglutition could still be carried on, though with difficulty. All the right side of the body was insensible and paralysed. The left side possessed sensation; the arm and leg of that side were agitated with convulsive motions. I advised the application of leeches to the throat, a blister to the nape of the neck, and a vomit. These re- medies employed, immediately produced all the effect which could be expected from them. It was then two o'clock in the evening; at five, the reollection began to return, the eyes had recovered their mobility, the paralysis and the convulsions had ceased. In the night there were PRINCIPLE OF LIFE. 225 several attacks of spontaneous vomitings, there also came on, in the same night, an hemor- rhage from the nose. The next morning, the patient was well, exclusive of some fatigue. It was the first time in her life that she had ever felt a fit of this kind. She had no symptoms of worms, nor were there any affections peculiar to dentition. She has ever since enjoyed good health. I shall conclude by saying a few words upon acephali. The principal questions to which these foetuses have given rise, are, to ascertain in what manner they can live and grow in the womb of their mother; and why they perish at different periods after birth, some continuing to live se- veral hours, and even several days, and others only a few moments. These questions no longer present any difficulties. The brain, whatever may be its other functions, and whatever may be the empire it exercises upon the actions of life, has no other immediate action upon the support of life, except by respiration, of which it con- tains the primum mobile. For we have seen that its action upon circulation and digestion does 2F 226 EXPERIMENTS ON THE not interest life, either in so coniderable or im- mediate a manner. Now so long as a fcetus is contained in its mother's womb, it has no need of breathing, and consequently the action of the brain on the mechanical phenomena of respiration through the diaphramatic and intercostal nerves, and that upon the lungs through the par vagum, becomes useless. I add that it can even live with- out its action upon the abdominal viscera, for there appears to be no digestion before birth. The brain, therefore, is not necessary to its life, and it may be entirely deprived of it, without ceasing to grow. It is in its medulla spinalis that it finds the principle of its existence and growth. But as soon as it is born, as soon as its mother no longer breathes for it, it must breathe for itself. If the brain is entirely wanting as far as the origin of the nerves of the eighth pair, it cannot perform any inspiratory motion, and it can only live the space of time during which, at that age, it can support asphyxia, from the moment that it ceased to com- municate with its mother. But whatever be the other parts of this viscera which are wanting, if the origin of the nerves of the eighth pair sub- sists, it may breathe, and will, in fact, breathe a PRINCIPLE OF LIFE. 227 longer or shorter time, according as this portion of the medulla oblongata is more or less perfect, and according as it is more or less protected from external agency. In those cases of adult animals in whom the brain has been found ossi- fied, the medulla oblongata never was observ- ed to be so. I am aware that cases are recorded of foetuses not only acephali, but in whom there did not exist any medulla spinalis. But besides that these cases are very few in comparison with those of simple acephali, it would be very important to ascertain whether these foetuses were born dead or alive, and this is what authors have not always mentioned. I know but of two instances in which we are assured that they have been born alive, without either brain or medulla spinalis (a). It is with these foetuses as with those which have been asserted to have been born, some without a heart, and others without any appear- ance of umbilical cord, and which are equally (a) Hist, de l'Acad. de Sciences, an. 1711, Obs. Anat. :;, et an 1712, Obs. Anat. 6. 228 EXPERIMENTS, &c. as unaccountable by physiology. To admit such extraordinary facts, it would require new and well authenticated observations. As to the foe- tuses still born and without medulla spinalis, it is easily conceived that some diseases, and among others hydrorachitis, could have de- stroyed this medulla in the mother's womb, and that death had been the result of it. REPORT MADE TO THE Class of Physical and Mathematical Sciences OF THE Imperial Institute of France, On the two first paragraphs of the preceding work* REPORT, $c. THE perpetual secretary of the class of physi- cal sciences certifies that the following is an extract from the proces verbal of the sitting of Monday, September 9th, 1811. The class having intrusted us, Mr. De Humboldt, Mr. Halle, and myself, to prepare a report upon the memoir read at the sitting of the third of June last, by Dr. Le Gallois, respecting the principle of the powers of the heart, and the seat of this principle, we shall pro- ceed to give the class an account of it, which may be as long as the memoir itself, because it requires details and elucidations, without which it would be difficult to estimate all the merit of this excellent work. It was not till after the discovery of the circula- tion of the blood, which Harvey completed and published in the beginning of the seventeenth 232 EXPERIMENTS ON THE century, that physiologists applied their attention to the cause and mechanism of the motions of the heart, which produced afterwards so many different systems. We shall not mention those of Descartes (a), nor those of Sylvius, of Le Boe (b), of Borelli (c); they are too absurd, and can only serve to prove how unfortunate were the first attempts made to explain one of the most important func- tions of the animal economy. We shall begin with the opinion of Willis, that is to say, by the distinction which he was the first to establish between the nerves destined to voluntary mo- tions, and those which preside over the functions independent of the will. He placed the origin of the latter in the cerebellum, and that of the nerves of voluntary motions in the cerebrum. (a) L'homme de Rene Descartes, et la formation du foetus avec les remarques dc Louis Laforgue, Paris 1677. p. 4 et 106. (b) Francisci Deleboc, Sylvii, opera medica. Genevas, 1681, p. 5. 27, 28,33, 475. (c) Joh. Alph. Borelli de motu animalium. Hagae Co mitum, 1743, p. 89, 92. PRINCIPLE OF LIFE. 233 He pretended that if the motions of the heart, as well as the other vital functions do not un- dergo any interruption, it is because the action of the cerebellum continues without ceasing; and that on the contrary, the motions subjected to the will require repose, because the action of the brain is not continual (a). This distinction of Willis was pretty generally admitted, till about the middle of the last century. It was especially on account of this system, that the division of the nerves of the eighth pair, from which almost all the cardiac nerves were supposed to arise, was performed in different countries. The de- sign was to prove by this assertion, that the heart receives all its motions from the brain; and it was said that the animals died of it, only because it destroyed the communications between these two organs. But besides that they die much later than they would if they perished from this cause, it has been well ascer- tained of late by several learned men, and es- (c) Tho. Willis opera omnia, edente Ger. Balsio. Am- stelodami, 1682. Tom. I. de cerebri anatome. Cap. XV. p. 50. 2 G 234 EXPERIMENTS ON THE pecially by Dr. Le Gallois, in a memoir, the insertion of which has been ordered by the class among those of the foreign litterati (a), that death is produced in those cases by an entirely different cause. Indeed it has some times happened that animals have died almost suddenly after the di- vision of the nerves in question; nor have the advocates of Willis failed to lay a great stress upon these experiments, of which their adversa- ries could not give any satisfactory explanation. But Dr. Le Gallois has demonstrated, in the memoir which we have just quoted, that this sudden death only takes place in certain species of animals, and then only when these animals were very young; and further, that it is the effect of a more or less complete asphyxia produced by the closure of the glottis. We can therefore find nothing, even in these facts, which affords any proof in favour of the opinion of Willis; and we may add, that the eighth pair does not arise from the cerebellum, and that it is not to this (a) This memoir is comprised in the third paragraph above. PRINCIPLE OF LIFE. 235 pair that the greatest part of the nerves of the heart belong. Boerhaave was of Willis's opinion; but be- sides the nervous action, he admits two odier causes of these motions, and of their harmony; to wit, the action of the blood of the coronary arteries on the fibres of the heart, and that of the venous blood on the internal surfaces of the cavities (cavites cardiaques) of the heart. It was the union of these three causes that occasioned the systole of the heart, and it was the simultaneous interruption of their action by the effect even of the systole which produced the diastole, during which these causes resumed their action (a). But this etiology, excepting what respects the stimulus of the blood, on the internal surfaces of the heart, was contradicted by facts;—which did not prevent it from pre- (a) Her. Boerhaave Instit. Medicae. §. 409. Vanswie- ten in aphorismos, &c. Lugduni Batav. 1745. Tom. II. p. 18. 236, EXPERIMENTS ON THE vailing in the schools, together with another not less celebrated error. We advert to Stahl and his soul, or Archeus, which either regulating all the motions of the living body, and submitting them to the will, or making them independent of it, as they may simply be useful or absolutely necessary for life, presides over all those of the heart, and through the nerves secure their duration and continuity; —a species of physiological reverie, which is repugnant to the true principles of the science. After all, where did the Stahlians place the residence of this simple and indivisible being?— In the brain, without doubt; but then how hap- pens it that an animal can live and the motions of its heart continue after decapitation? Will they assign the heart itself for its seat?—But all ani- mals, and especially the cold-blooded ones, out- live a longer or a shorter time the excision of this organ (a), (a) See for the exposition and refutation of this sys- tem, Haller's Elem. Physiol, torn. I. p. 480—8. et torn. IV. p. 517—34. PRINCIPLE OF LIFE. 237 Other authors, such as Abraham Ens (a), Stoehelin (b) &c. have also endeavoured to ac- count for the motions of the heart; but their systems, almost as soon forgotten as they were conceived, do not deserve our notice. Those of Boerhaave and Stahl were nearly the only ones which prevailed, when, in 1752, Hal- ler published his experiments on irritability. These experiments, as well as those which his followers published afterwards, tend to prove that the contractile property belongs exclusively to the muscular fibre. This property, which Haller designates sometimes under the name of vis incita, at others, after Glisson, under that of irritability, is the source of all the motions which take place in the animal; but it cannot produce them unless some cause, some stimulus deter- mines it to act. Thus every muscular motion always supposes two things, the irritability which produces the contraction .of the muscle, and a (a) Dissertatio physiol. de causa vices cordis alternas producente. Lugd. Batav. 1745. (6) Dissertatio de pulsibus. Basileae, 1749. 238 EXPERIMENTS ON THE stimulus which determines the irritability to commence its action. The irritability is every where the same; its force alone varies in the se- veral muscles, but does not obey the same stimu- lus in all the muscles. The nervous power is the natural stimulus of all those which are submitted to the will; and it is by exciting or suspending the action of this power upon the irritability of certain muscles, that the will causes such part to act, or sets it at rest. It is not so with the involuntary muscles. These acknowledge stimuli of various sorts, which are appropriated to their functions, and wholly abstracted from the nervous power. The blood is the natural stimulus of the irritability of the heart; it is the alimentary substances that stimulate that of the intestinal canal, &c. In these principles we readi- ly find the explanation of the principal circum- stances which are observed in the motions of the heart. Thus those motions are not submitted to the will, because they are independent of the nervous power; they continue without interrup- tion during life, because the irritability by which they are produced belongs essentially to the fibres of the heart, and because the blood by which they are directed is constantly brought PRINCIPLE OF LIFE. 239 back to this organ by the veins in proportion as it is taken away by the arteries. The systole and diastole alternately and regularly succeed each other, because the stimulus of the blood always produces the systole whether in the auricles, or in the ventricles, and because the systole, by destroying the stimulus, is the cause of the diastole, which brings back the systole, by al- lowing a new influx of blood. Such is summarily the celebrated theory of the Hallerian irritability; this theory had not been, as all the others we have mentioned, con- trived in the closet; it was grounded upon expe- riments made by Haller himself and his most distinguished disciples, who ranked first among the anatomists and physicians of the last cen- tury. These experiments which were repeated throughout Europe, met almost every where with partisans; but there were also found a cer- tain number of censors of great reputation. The principal point of this difference of opinion, the object of disputes to the present day, consists in ascertaining whether the motions of the heart are really independent of the nervous power. 240 EXPERIMENTS ON THE The facts upon which the Hallerian school has maintained the affirmative may be reduced to three heads: First, If you cut off all commu- nication between the heart and the brain, the only source of nervous power, by the division of the nerves which are distributed to the heart, by that of the medulla spinalis in the neck, or even by decapitation, the motions of the heart continue as before. Second, If you take out the heart of a living animal and lay it on a table, this organ continues to pulsate, and sometimes for a very long time, (M. De Humbolt shewed us that it pulsated more strongly and for a longer time, when it was held suspended.) Third, Convulsions are always produced even some- times after death, in the muscles which belong to voluntary motions, by irritating the nerves of those muscles, either in a mechanical, or in any other way. The irritation of the cardiac nerves on the contrary, causes no alteration in the motions of the heart, nor does it re-excite them when they have ceased; it is so with the irritation of the medulla oblongata and spinalis, which occasions strong convulsions through PRINCIPLE OF LIFE. 241 all the body, and produces no effect upon the heart. These facts are correct, except perhaps those of the third head, upon which there is some difference of opinion. But in admitting them, the adversaries of irritability have demanded, how happens it, if the nervous power does not act upon the heart, that this organ should re- ceive nerves? And why is it found so eminently submitted to the empire of the passions? Haller has never given clear answers to their objec- tions, but every thing proves that he was aware of all their force. When we read with attention all that he has said upon the motions of the heart, in his memoirs upon irritability (a), and espe- cially in his great work on physiology (b), we are struck with the contradictions with which it abounds, and which renders its perusal fatigu- ing. His great object is, every where, to prove that the motions of the heart are independent of (a) Memoires sur la nature sensible et irritable des parties, etc. Lausanne, 1756.—Opera minora, torn. I. (6) Elem. Physiol, lib. IV. sect. V. et lib. XI sect III. 2H 242 EXPERIMENTS ON THE the nervous power; every fact, experiment and observation which he cites, tends to this object. Nevertheless, he seems to admit in several places, that the nerves have an action upon the heart; it is true that it is with an air of doubt that he admits it, confining himself to say, that it is possible, that it is not improbable, that the heart borrows a moving power from the nerves (a). These contradictions, with which he was charged by several justly celebrated authors, among others by Messrs. Prochaska (b), Beh- rends (c), and Ernest Platner (d) &c, evidentiy proceed fiom the impossibility of reconciling the result of his experiments, with the inter- vention of the nervous power in the motions of the heart; and that by rejecting this interven- tion, he could not account either for the use of the cardiac nerves or for the influence of the passions on the heart. For this is the real cause (a) Ibid. lib. IV. sect. V. p. 493, et alibi passim. (*) Opera Minora. Viennae, 1800, torn. II. p. 90. (c) Tom. III. p. IV. of Ludwig's collection, entitled Scriptores Nevrolog. Minorcs Selecti. Lipsiae, 1791-5. IV. torn, in 4to. (d) Tom. II. p. 269, of the same collection. PRINCIPLE OF LIFE. 243 of difficulty in the controversy in question. Those who, like Fontana, have formally rejected all intervention of the nervous power, have been forced to admit, that the nerves destined in every other part to carry life, sensation and motion, had no known use in the heart (a). Such consequences, evidently betrayed the insufficiency of the theory of Haller. Hence, several of his followers have acknowledged the necessity of modifications, and of admitting the nervous power, as one of the conditions upon which irritability depends. From that time, they have been able to account for the use of the nerves of the heart, and the power of the pas- sions upon this organ. But, from the moment they wished to account for the motions of the heart not being stopped, by the entire suppres- sion of all communication between the brain and the heart, they were obliged to abandon the opinion generally received, by which the (a) Memoires sur les parties sensibl. et irritab. torn. III. p. 234. See also Caldani, ibid. p. 471; et le traite surle venin de la vipere.tom. II. p. 169,171. 244 EXPERIMENTS ON THE brain is considered as the center and the only source of the nervous power; and they admit- ted without direct proofs, that this power is produced in the whole extent of the nervous system, and even in the smallest nerves, and that it can exist independently of the brain, for a certain time, in the nerves of every part. Among the authors of this last opinion, the learned professor Prochaska is one of those who have best described it (a). But when he comes to apply it to the motions of the heart, and endeavours to explain why they are independ- ent of the will, and are submitted to the power of the passions, his opinion is not completely decisive. It is to the ganglions he has recourse, and then he hesitates as to the functions he is to ascribe to them. Sometimes he considers them as knots, as ligatures tight enough to intercept all communication between the heart and the sen- sorium commune, in the calm and quiet state, but not sufficiently so, as to prevent the sensorium (a) Commentatio de functionibus systematis nervosi, published in 1784, in the third Fascicule of the Annota- tiones Acad, of this author, and re-published in his Opera minor. Vienna, 1800. PRINCIPLE OF LIFE. 245 from re-acting with more or less energy upon the heart, in the agitation of the passions (a). Sometimes, he seems to think that the inter- ception is complete and continued; that it is through the nerves of the eighth pair, that the effect of the passions is felt upon the heart (b); and he seems to adopt the opinion of Winslow (c), revived by Winterl (d), by Johnstone (e), by Unzer (/), Lecat (g), Peffinger (h) &c, namely, that the ganglions are so many little brains. He admits at the same time, that the nerves of sensation are distinct from those of motion, so that the heart cannot contract itself, unless the impression of the stimulus upon its cavities is transmitted to the ganglions through (a) Opera minor, torn. II. p. 165. (b) Ibidem p. 167. (c) Exposition anatom. Traite des nerfs. sect. 364. (d) Novainflam.theoria. Viennae, 1767. cap. 5. p. 154. (e) Essay on the use of the ganglions. 1771. (/) Quoted by Prochaska, opera minor, torn. II. p. 169. (g) Traite de l'existence, de la nature et des proprietes du fluide nerveux. Berlin, 1765, p. 225. (A) De structura nervorum, Argentorati. 1782, sect. I. §. 34, sur la fin. Inserted in the collection of Ludwis*. vol. I. 246 EXPERIMENTS ON THE the nerves of sensation, and thence reflected to the fibres through the nerves of motion (a). But besides that the whole of this opinion is, from the confession of the author himself, a simple conjecture, it supposes in the first place, that circulation should continue after the de- struction of the medulla spinalis; and, secondly, that the heart should cease to pulsate, at the instant when its communications with the gan- glions and the plexuses are interrupted: now, these suppositions are disproved by the facts. Such fruitless endeavours to modify the theory of irritability, by the intervention of the nervous power, have only increased the zeal of some authors to maintain this theory in its pri- mitive purity; and as the use of the nerves of the heart was one of the most difficult parts of this theory, Soemmering, one of the most pro- found anatomists of Germany, and Behrends, one of his most distinguished disciples, main- tained in 1792, that the heart has no nerves, (a) Opera minor, torn. II. p. 169. PRINCIPLE OF LIFE. 247 and that all those which appear to be distri- buted to this organ, lose themselves in the coats of the coronary arteries, without one single filament being received by its own fibres (a): an opinion which, so far from removing all the difficulties, would only render the influence of the passions upon the motions of the heart still more inexplicable. These two authors pre- tend that the cardiac nerves serve to keep up and increase the irritability of the coronary arte- ries;—but the existence of irritability in the arteries is still dubious, and if it were demon- strated, it would be very strange that it should depend upon the nervous power in the arteries, and that it should be entirely independent of it in the heart, the most irritable of all organs. In other respects, science could only gain by the doubts proposed by Behrends, doubts unat- tended with proofs on the cardiac nerves, since they determined the learned Scarpa in his turn to enter the lists, and they have been the means of (a) Behrends, dissertatio qua demonstratur cor nervis carere. Moguntiae, 1792. Inserted in the third volume of the collections of Ludwig. 248 EXPERIMENTS ON THE producing his beautiful work upon the nerves of the heart (a). Scarpa proves in this work, that the nerves are as numerous and are distributed in the same manner in the heart as in the other muscles. Like Prochaska, he admits that sensi- bility and irritability are essentially united, and that the nervous power is generated through the whole extent of the nerves; but he does not admit that the ganglions are so many little brains (b); he appears to think that the nervous power, such as it exists throughout the nerves, is of itself sufficient for the exercise of the various functions; and that it only wants a sti- mulus to be brought into action. It is from the brain that the stimulus of the muscles submitted to the will proceeds; and in the usual state the blood is the stimulus of the heart; but in the strong emotions of the mind, the brain becomes also the stimulus of this organ (c). (a) Tabulae nevrologics ad illustrandum historiam anatomicam cardiacorum nervorum, etc. Ticini, 1794. (b) Ibid. sect. 30. (c) Ibid. sect. 22. 24, 25, 26, 27. 29. PRINCIPLE OF LIFE. 249 In conformity with this opinion, the heart should pulsate in the same manner, and with the same force after decapitation, and after the destruction of the medulla spinalis, and after it has been extirpated. Scarpa himself compares the pulsations which take place in apoplexy, to those observed when the heart has no further communication with the brain nor the medulla spinalis (a), but we shall see by and by that this is far from being the case. In other respects we ought not to omit a very important remark of this author,' which it is surprising should not have been made before. It respects the passive state of the heart, when the medulla spinalis and cardiac nerves are irritated. Scarpa ob- serves that this passive state, about which so much has been said, and which is considered as" a demonstrative proof that the motions of the heart do not depend upon the nerves, proves only that the nerves of the heart are not of the same order as those of the voluntary muscles, and that the nervous power is not ex- ercised in the same manner (6). This reflec- (a) Tabulae nevrologicae, Scc.sect. 25. 0) Ibid. sect. 20. 21 25Q EXPERIMENTS ON THE tion is without doubt very judicious, and it is through an error of experimental logic that we have been surprised not to obtain the same effects from the irritation of two orders of nerves which were entirely different. The work of Scarpa did not alter Dr. Soem- mering's opinion (a); nor did it prevent Bichat from denying that the nervous power has any share in producing the motions of the heart (b). This latter'author, while he acknowledges an animal and an organic life distinct from each other, admits a nervous system for each of these two lives. The system of the ganglions, which like the above mentioned authors, he considers as little brains belonging to organic life, and the cerebral system to animal life (c). To be con- sistent with himself, Bichat ought to have admitted, like Prochaska, that the heart being (a) Th. Soemmering de corporis humani fabrica. Tra- jecti ad Maenum 1796. Tom. III. p. 30, 43, 46, 50, et ibid. 1800. Tom. V. p. 43. (b) Recherches physiol. sur la vie et la mort. Paris, an. 8-1800. Part. II. art. 11, § 1. (c) Ibid. Part. I. art. 6. § 4. PRINCIPLE OF LIFE. 251 the center of organic life (a), receives from the ganglions the principle of its motions; but he did not; he was thrown into this inconsistency chiefly by galvanic experiments, having in vain tried to produce contractions in the heart by galvanizing the cardiac nerves; experiments upon which Soemmering and Behrends had also endeavoured to establish their opinion. How- ever, these experiments might have succeeded, as was ascertained by one of us in 1797 (b) and three years before by Fowler (c). Such is the succinct but faithful account of the principal systems by the aid of which it has been attempted, from the discovery of the circulation down to this day, to account for the motions of the heart. On a general retrospect view of these systems, we remark, that in all those (a) Ibid. art. 1. § 2. (A) M. De Humboldt, experiences sur l'irritation de la fibre nerveuse et musculaire, published in 1797, and translated into French two years after. Tom. I. chap. 9. (c) Experiments on animal electricity, 1794. By Richard Fowler. g«|2 EXPERIMENTS ON THE maintained before Haller (a), the nervous power is always considered, sometimes in one relation, at others in another, as one of the conditions which are essential to the production of the mo- tions of the heart, and it has ever been in the brain only that they placed its seat. The cardiac nerves therefore had a determined use in all those systems, and it was easily comprehended in what manner the heart was submitted to the power of the passions; but it was impossible to explain why circulation continues in the acephali, or why, in experiments made upon animals, the interception of all communication between the brain and the heart does not stop the motions of the latter. Ever since the days of Haller, irri- tabilitv has been the basis of all systems. When we consider this property as being essential to the fibre and as independent of the nervous power, circulation in the acephali and the various phenomena observed in the experiments just mentioned had nothing puzzling; but the use of the nerves of the heart, and the influence of (a) And also in Ens, de Stoehelin, and others of whom we have not spoken. PRINCIPLE OF LIFE. 253 the passions upon this organ became inexplica- ble. The necessity of removing these difficulties produced two sects among the partisans of irri- tability. Some who were the zealous advocates of pure irritability, called in to their assistance the most improbable hypotheses, and all their efforts only serve to prove how difficult the cause they have embraced is to defend. Others had introduced the nervous power in irritability which they considered as one of the functions of this power; but whether on account of its seat, or the state of the nervous power, they were obliged to admit conditions which, by their own confession, are far from being demonstrated, respecting which they do not agree among themselves, and which, in the application they make of them to the motions of the heart, either do not entirely remove the old difficulties, or give rise to new ones. It is easy to perceive the cause of so little pro- gress having been made in elucidating this great and extensive question. If we examine all that -has been said on this subject since the days of Haller, we find that nearly the same facts, the 254 EXPERIMENTS ON THE same experiments, and the same reasonings have ever been brought forward on both sides. The only new experiments are those applications of galvanism to stimulate the cardiac nerves. And these are only apparently new, for in the time of Haller electricity had been employed in the same view (a). It is evident that science had nothing to hope from following the paths which had been trodden by so many celebrated men, for nearly sixty years. New roads were to be opened; new methods were to be contrived, in order to interrogate nature; but above all it was necessary to introduce in physiological experi- ments that precision and strict logic to which other physical sciences have in our days been indebted for the very great progress they have made;—and this is what was performed by the author of the memoir of which we here give an account. Dr. Le Gallois's intention was not to investi- srate the causes of the motions of the heart; he o (a) See, among others, Mem. sur les parties sensib. et irritab. Tom. III. p. 214. PRINCIPLE OF LIFE. 255 was satisfied with the theory of HaUer, when experiments, undertaken with quite different views, led him to so extraordinary a result, that he could no longer understand his own experi- ments, unless he should ascertain whether and how the nervous power intervenes in the func- tions of the heart? The better to understand his work, we shall relate on what occasion, and by what chain of facts and reasoning, he found himself engaged in this inquiry. A particular obstetric case, a few years ago, made him desirous of knowing how long a full grown foetus may live without breathing, from the moment when, from any one cause, it has ceased to communicate with its mother? This question which is curious in itself, and very interesting for the practice of midwifery and me- dical jurisprudence, had scarcely been touched by authors: Dr. Le Gallois undertook to resolve it by direct experiments made upon animals; and in order that his answer might apply to the greatest number possible of cases, he placed the foetuses of the animals in the various states, which resembled the principal accidents which may 255 EXPERIMENTS ON THE happen in the human foe;us, at the same time that it ceases to communicate with its mother. Among these circumstances, one which happens but too often, is the separation of the head in the artificial delivery by the feet. The author wished to know what becomes of the ioetus in this case: whether it perishes at the very instant of decol- lation, and of what kind of death it dies. He found that the trunk continues alive, and that, by preventing the hemorrhage by the ligature of the vessels of the neck, it only dies after the same length of time, and death is only attended with the same phenomena, as if without the separation of the head respiration had been completely suppressed; and what completed his demonstra- tion that the decapitated animal is in fact only asphyxiated is, that its existence can be pro- tracted ad libitum by supplying the want of natural respiration by the inflation of the lungs. Dr. Le Gallois concluded from these facts, that decollation does nothing more than arrest inspiratory motions, and that consequently the principal of all these motions resides in the brain; but that the principle of the lite of the trunk is PRINCIPLE OF LIPE. 257 in the trunk itself. In investigating afterwards, where the immediate seat of each of these two principles resides, he discovered that the princi- ple of the inspiratory motions, is seated in that part of the medulla oblongata which gives rise to the nerves of the eighth pair; and that the princi- ple of the life of the trunk, has its source in the medulla spinalis. It is not by the whole of this medulla that every part of the body is animated, but only by that portion from which it receives its nerves; so that by destroying only one por- tion of the medulla spinalis, those parts of the the body which correspond to that portion, are alone affected with death. Further, by intercept- ing the circulation of the blood in a portion of the medulla spinalis,life is weakened and soon wholly extinguished in all the parts which receive their nerves from that portion of the medulla. There are two modes therefore of causing the cessation of life in any particular part of the body of an animal: the one by destroying the medulla from which this part receives its nerves, the other by intercepting in it the circulation of the blood. 2K 258 EXPERIMENTS ON THE It thence resulted, that the support of life in any one part of the body drpended essentially upon two conditions; namely, the integrity of the corresponding portion of the medull spi- nalis, and tne circulation of the blood; and con- sequently that it would be possible to keep up life in any one part of an animal, as long as these two conditions can be made to exist; that we may, for example, keep alive the anterior part alone, after having occasioned death in the pos- terior, by the destruction of the corresponding portion of the medulla spinalis; or the posterior, after ha\ ing cau td the death ol the anterior. Dr. Le Gallois, whose method has constantly been, to seek in direct experiments the con- firmation of the consequences which he had drawn from preceding ones, was desirous to know whether it would be really possible, thus to keep alive any one portion of an animal alone, after having caused the death of the rest of the body. He first submitted a rabbit twenty days'oldto these inquiries, by destroying in that animal, all the lumbar portion of the medulla spinalis. This operation, in no ways wounding PRINCIPLE OF LIFE. 259 immediately the rest of the medulla spinalis, and circulation not being, according to the theory of Haller, to be affected by it, there was every reason to expect by reasoning from the preced- ing experiments, that the animal would have outlived it a considerable space of time; and that it would not have died, except in consequence of the symptoms which were to be produced by so severe a wound: but respiration stopped be- tween one and two minutes after, and in less than four minutes it gave no signs of life. The same experiment, repeated several times, was always attended with the same result, nor could it be prevented; and it was established that a rabbit, twenty days old, cannot outlive the loss of the lumbar portion of the medulla spinalis, which was the more surprising, as the rabbits of that age will continue to live after decapi- tation, that is, after the entire loss of the brain. This fact, the author could not reconcile with his preceding experiments, and it is this which led him to the discovery, that the princi- ple of the power of the heart resides in the giedulla spinalis. 2£0 EXPERIMENTS ON THE Dr. Le Gallois first ascertained, that the de- struction of each of these two portions of the medulla spinalis, (viz. the dorsal and cervical) was as mortal in rabbits of twenty days old, as that of the lumbar portion, and even in a shorter time, to wit, about two minutes; he then found that the same experiments repeated upon rab- bits of different ages did not give the same re- sults; in general, the destruction of the lumbar portion of the medulla spinalis, is not suddenly mortal in these animals before they have attain- ed the age of ten days; st veral outlive it still at the age of fifteen. Beyond twenty days the effect is the same as at twenty. Very young rabbits may likewise continue to live after the destruction either of the dorsal portion of the medulla or of the cervical; but for a shorter time, and less frequently after the destruction of the latter, than after that of the dorsal. None can outlive either beyond the age of fifteen days. In all these partial destructions, even when death is sudden, it is never instantaneous, except in the parts which receive their nerves from the PRINCIPLE OF LIFE. 261 medulla destroyed; but it only takes place in the rest of the body after a certain but determined time, which no means can protract. This length of time, which is the same in all animals of the same species and age, is longer in proportion as the animals are younger. For instance, when the cervical portion of the medulla is destroyed in young rabbits, life is destroyed at the instant in the whole neck; but it continues in the head, and this is known by the gapings it excites. It continues likewise in the posterior parts from the shoulders, as is fully testified by the sensa- tion and voluntary motion that are preserved. In the first day after birth, the gapings last about twenty minutes, the sensibility and mo- tion of the rest of the body fifteen minutes. At the age of fifteen days, the duration of the gap- ings does not exceed three minutes, nor that of sensibility or motion two minutes and a half. Lastly, at the age of thirty days, the gapings cease at between one and one minute and a half, and sensibility at one minute. After the destruc- tion of the dorsal portion of the medulla spinalis, it is the breast, and not the neck, that is affected with death; in other respects there are the same 262 EXPERIMENTS ON THE phenomena of the same duration. If the three portions of the medulla are destroyed at the same time, the gapings, the only signs of life then existing, still have, at the different ages, the duration which we have just indicated. The author, who had so often performed de- capitation upon rabbits of different ages, had constantly remarked, that the head when sepa- rated from the body, continues to gape during a time determined for every age. This length of time was evidently the same as after the destruction of the medulla spinalis. Now it is evident that after decapitation, there can be no circulation in the head, and that the gapings which t«ke place in this case, only continue while life exists in the brain, after the entire cessation of circulation. This was the first notice that Dr. Le Gallois had, that when the partial destruction of the medulla spinalis has oc- casioned life to cease in all the rest of the body, it is because it suddenly stops the circulation. In order to ascertain it, he cut out the heart at the origin of the large vessels in rabbits, every five days, from the moment of their birth to the PRINCIPLE OF LIFE. 263 age of one month; and having noted with care, the duration of the different signs of life from the moment when the circulation had been stopped by that means, he found that those periods of duration were precisely the same, as those he had observed after the destruction of the me- dulla spinalis; he might have considered this approximation as sufficient to decide the ques- tion, but he wished to ascertain in a more direct manner, if the circulation be really stopped at the very instant when the medulla spinalis is de- stroyed. The absence of the hemorrhage and the emptiness of the arteries were the most evident signs of it that he could deduce; and he found in fact, that as soon as the operation is performed, the carotids are empty, and the am- putation of the limbs furnishes no blood, though performed very near the trunk and before life is extinct in the parts, the medulla of which had not been destroyed. In a word, all the signs which may serve to show the state of the circulation, demonstrated that whenever the destruction of any one portion of the medulla spinalis causes death suddenly in the rest of the body, it is occasioned by the arresting of 264 EXPERIMENTS ON THE that function. This latter effect takes place, not because the motions of the heart cease at once,. but because they lose all their energy, so as not to have power to propel the blood as far as the carotids. It thence results, that it is from the medulla spinalis, wholly and exclusively, that the heart receives the principle of its energy, since the destruction of any one of these three portions may stop the circulation. It further results, that every part of the spinal marrow, exercises on life two very distinct modes of action: one by which it constitutes it in every part which re- ceives nerves from it; the other by which it constitutes it in every part of the body, by con- tributing to furnish to all the organs, which re- ceive filaments from the great sympathetic, and particularly to the heart, the principle of power and of life, without which they cannot per- form their functions. It is clearly perceived, therefore, that in order to keep the anterior or posterior parts of an ani- mal alone alive, after producing death in the PRINCIPLE OF LIFE. 265 rest of the body, by the destruction of the me- dulla corresponding with it, one should be able to prevent this destruction from stopping circu- lation. Now, this is very easily accomplished by diminishing the sum of power which the heart is to dispense, to keep up circulation in proportion as that of the power which it receives from the medulla spinalis is diminished. For this purpose it will be sufficient to decrease, by ligatures made upon the arteries, the extent of the parts where the heart is to distribute blood. We have observed, for instance, that the de- struction of the lumbar portion of the medulla spinalis is quickly mortal in rabbits of twenty or more days old; but it does not kill them, if, before producing it, the abdominal portion of the aorta has been tied between the caeliac and anterior mesenteric arteries. The application of this principle to other parts of the body, leads to a case apparentiy very singular, which is, that in order to keep up life in rabbits of a cer- tain age, after having destroyed their cervical medulla, their heads must first be cut off; if this medulla be first destroyed without decapitation, they are irrevocably dead. But our astonish- 2 L 256 EXPERIMENTS ON THE ment will cease when we reflect, that' by decapi- tation, we withdraw the whole head from the influence of circulation, and that by this opera- tion, the heart requiring less power to continue its function, it may be weakened by the de- struction of the cervical medulla, without ceas- ing, to perform it. It is likewise easily conceivable, that any other operation capable of suspending or consi- derably retarding circulation in a certain extent of the body of an animal, ought to produce a similar effect, and also furnish the means of at- tacking with impunity such portion of medulla spinalis, the destruction of which would have been mortal, had it not bee n fbr this previous operation. This is what is ol Gained by the very- effect of the destruction of the medulla. This destruction produces two effects upon circula- tion; by one, general circulation is weakened, by depriving the heart of the contingent of power which it receives fiomthe medulla de- stroyed; by the other, without wholly stopping circulation in those parts affected with death, it lessens it in a very high degree, whkh is equi- PRlNCIPLE OF LIFE. 267 valent in a certain measure to >the iigatures made upon the arteries of those parts. But .this effect is sensibly felt only a few minutes after the destruction of the medulla. Thence it hap- pens that the destruction of a first portion of medulla spinalis furnishes the ineans of destroy- ing a second; this latter a third, and so on. For instance, when by decapitating a rabbit we are •enabled to destroy the cervical medulla, the de- struction of this medulla furnishes in some •minutes the means of destroying one fourth part of the dorsal medulla; and by continuing thus to operate at intervals upon similar lengths of this same medulla, we shall be able to ac- complish the whole destruction without stop- ping-circulation, which is then supported by the lumbar portion of the medulla spinalis alone. From what we have just stated, it may be concluded that, in rabbits, any one portion of the medulla spinalis supplies the heart with suffi- cient power to maintain circulation in all the parts which correspond to that por|ion;.and that consequently, by cutting a jabbit transversely 0(Jg EXPERIMENTS ON THE and into portions, it would be possible to keep alive separately and indefinitely each portion, if both the lungs and the heart, which are neces- sary for the formation and circulation of the arterial blood, could be a part of them. But they can only be a part of the chest; and it is fully in our power to maintain life in the chest alone, and when separated, after having cut off the anterior and posterior parts, and prevented the hemorrhage by suitable ligatures; and this is practicable upon rabbits of thirty days and upwards. Such are the principal results of the researches of Dr. Le Gallois. These results, all produced by one another, and which furnish one another a mutual support, are grounded upon direct experiments, made with a precision till now un- known in physiology. We shall now state such of these experi- ments as the author has repeated in our pre- sence. We have bestowed on these repetitions, three sittings, each of several hours; and to avoid every precipitation, and allow ourselves PRINCIPLE OF LIFE. 269 time to weigh the facts at leisure, there has been an interval of one week between each sitting. EXPERIMENTS Repeated before the Commission of the Institute* We shall divide them into two paragraphs. The first will comprise those which tend to prove that the primum mobile of all inspiratory motions reside in that part of the medulla ob- longata which gives rise to the nerves of the eighth pair. In the second we shall describe those, the object of which is to show that the powers of the heart have their origin in the me- dulla spinalis. SECTION I. Experiments relative to the Principles of Inspiratory Motion. The author took a rabbit five or six days old; he separated the larynx from the os hyoides, and laid the glottis bare, that we might observe its movements; after which he opened the cranium, then took out the cerebrum and afterwards the cerebellum. After this double extraction, the inspirations continued; they were characterised 270 EXPERIMENTS ON THE each by four movements, which took »plaoe at the same time; namely, a gaping, the opening of the glottis, the elevation of the ribs, and the contraction of the diaphragm. These four motions having been well ascertained, and being to last for a certain time, according to the age of the animal, the author extracted the medulla oblongata;—and at the same instant these mo- tions ceased all at once. We found that the ex- tracted portion of medulla oblongata extended as far as the great occipital foramen, and that in it was included the origin of the nerves of the eighth pair. The same experiment was repeated upon another rabbit of the same age, with this differ- ence, that after the extraction of the cerebrum and the cerebellum, instead of taking away at first, as great an extent of the medulla oblon- gata, it was extracted successively by slices about three millimetres in thickness, (a little more than the twelfth part of a French inch*) The four inspiratory motions continued after the extraction of the three first slices; but they were suddenly stopt after that of the fourth. PRINCIPLE OP LIFE. 271 It was ascertained thoB the third sfice ended in the posterior part and near the pons varolii, and that the fourth included the origin of the nervesof the eighth pair. The same experiment, repeated upon several other rabbits, was constandy attended with the same results. He proceeded in the same manner upon a cat five weeks old, only he separated the two re- current nerves before he had extracted by slices the medulla oblongata. Upon this the glottis Closed, and it remained motionless in that state; but the three other motions, .namely, gaping, elevation of the ribs and contraction of the dia- phragm, continued, nor did they stop till the moment he took off from the medulla oblon- gata the origin of the nerves of the eighth pair. It is evident that if instead of destroying this part, in which the primum mobile of all inspU ratory motions reside, one should confine one- self to preventing it from communicating with the organs which perform those motions, 272 EXPERIMENTS ON THE the same effect would be produced; that is to say, that those motions, the organs of which would no longer communicate with the part in question, would be suppressed. This is what we have just observed in the cat, in which the section of the recurrent nerves suppressed the motion of the glottis without stopping the three other motions. To suspend these in the same manner, it is sufficient to notice thiough what channel their organs communicate with the me- dulla oblongata. Now, it is clear that it is through the intercostal nerves, and consequendy through the medulla spinalis, that the medulla oblongata acts upon the muscles which raise the ribs, and that it is through the phrenic nerves and consequendy again by the medulla spinalis, that it acts upon the diaphragm. When we divide the medulla spinalis upon the last cer- vical vertebra, and above the origin of the phrenic nerves, we must suppress the mo- tions of the ribs, not those of die diaphragm; —and when we divide this medulla between the occiput and the origin of the phrenic nerves, we must cause a sudden cessation of all the movements of the ribs and of the dia- PRINCIPLE OF LIFE. 273 phragm at once. This is, in fact, what takes place. The author took a rabbit about ten days old, and after attentively examining the motions of the thorax, he divided the medulla spinalis upon the seventh cervical vertebra; at that instant the motions which depend upon the raising of the ribs were stopped; but the contractions of the diaphragm continued: he again divided the medulla spinalis at the first cervical vertebra, and the contraction of the diaphragm immediately ceased. Finally, he cut the eighth pair at about the middle of the neck, and the motions of the glottis were suppressed. Thus, of the four inspiratory motions, there were left only the gapings, which proved that the medulla oblongata still preserved the power of producing them all, and that it only exer- cised it without effect in regard to the three others, because it no longer communicated with their organs. Here we are to observe, that several authors, among others Arnemann, had remarked, before Dr. Le Gallois, that the section of the medulla spinalis did not stop the motions of the diaphragm, unless k were performed be- tween the occiput and the origin of the phrenic 2M 274 EXPERIMENTS ON THE nerves. But these authors consider the brain as the only source of life and of all the motions of the body. They thought, in conformity with this opinion, that the section of the medulla spinalis paralyzed instantaneously every part of the body which received its nerves from that medulla below the section, and that conse- quently when the section was formed near the occiput, the diaphragm ceased its contractions, because it partook of the palsy of all the parts below the section. But Dr. Le Gallois has de- monstrated that the section of the medulla, per- formed at the first or the last cervical vertebrae, only stops the inspiratory motions, and that it allows the existence of sensation and voluntary motion through the whole body. This distinc- tion is important: no one had made it before him. It is not only in warm-blooded animals, that these experiments are observed with the results we have just stated. To prove that these results depend upon the general laws of the animal economy, and that the nervous power is distri- buted and governed in a uniform manner in all animals which possess vertebra;, the author PRINCIPLE OP LIFE. 275 took a frog, and after remarking that, in these animals, which possess neither ribs nor a dia- phragm, there are only two kinds of inspiratory motions; namely, those of the glottis, which is opened in the form of a lozenge, and those of throat, which is raised and lowered alternately; he took off one half of the cerebrum,—both motions continued: he then destroyed about one half of what was left of that viscus,—the same motion continued: finally, he carried the destruction of the brain as far as near the great occipital foramen, and both motions were in- stantaneously stopped for ever. The medulla spinalis of another frog was cut off upon the third vertebra,—the inspiratory motions con- tinued. It was afterwards separated, between the occiput and the first vertebra of a third frog, and at that instant, the motions of the throat which correspond with those of the dia- phragm ceased. After these two last experi- ments, the frogs were, and have continued alive both in the head and in the rest of the body, but they were unable to govern themselves, and were, in this respect, in the same case with the first, the brain of which had been destroyed. EXPERIMENTS ON THE SECTION II. Experiments relative to the Principle of the Power of the Heart. THE author first proved that life always con- tinues a certain time, even in warm-blooded animals, after the total cessation of circulation; and that this time is determined according to the age. For this purpose he opened the thorax, and extracted the heart of a rabbit five or six days old, and he did the same on another, ten days old. In the first the gapings ceased seven minutes after, and sensibility four, from the exci- sion of the heart. In the second, the gapings lasted four minutes, and sensibility but three. The cer- vical and a small portion of the dorsal medulla, were then destroyed on another rabbit of the same litter as the last, and the pulmonary in- flation was immediately performed; but notwith- standing this assistance, the gapings ceased three minutes and a half after, and sensibility a little after two and a half minutes; a duration which, as may be observed, coincides within one half PRINCIPLE OF LIFE. 277 a minute with those observed after the excision of the heart. To prove that, in this experiment, it is really by arresting circulation that the destruction of a part of the medulla causes the cessation of life in the rest of the body, the author took a rabbit of the same age with the two last: he first divided the medulla near the occiput. After this section, the carotids were black, but round and full, and the amputation of a leg fur- nished black blood. The pulmonary inflation having been performed, the carotids soon grew of a fine vermillion colour, and the hemorrhage assumed the same. These signs leave no doubt that the circulation had continued after the divi- sion of the medulla, near the occiput. The au- thor destroyed on this rabbit, the same portion of medulla as on the preceding, and immediately the carotids appeared flaccid, and soon after empty and flat. Both thighs, amputated in less than two minutes after the destruction of the medulla, did not furnish one drop of blood. 278 EXPERIMENTS ON THE The destruction of the cervical medulla, per- formed on sever .:1k? rabbits, from twenty to thirty days old, furnished exactly the same results; i. e. the carotids emptied themselves, very soon after the amputation of the limbs furnished no blood, and, notwithstanding the pulmonary inflation performed with the utmost care, all the signs of life had almost only the same duration with those observed in the cases of the excision of the heart, according to the tables which Dr. Le Gallois has given in his memoir for the different ages. After the destruction of the medulla dorsalis, the same results occurred, as it regarded the vacuity of the carotids, the absence of the he- morrhage, and the duration of life. The destruction of the lumbar medulla on rabbits aged four or five weeks, gave similar results, with this simple difference, that circula- tion did not stop instantaneously, as after the destruction either of the cervical or the dorsal medulla, but only about two minutes, and in one case about four minutes after; which proves PRINCIPLE OF LIFE. 279 that the action of the lumbar portion of the me- dulla on 'he heart, though very real and very great, is not as immediate as that of each of the two other portions. After proving, by these experiments, that cir- culation depends upon all the portions of the medulla spinalis, the author convinced us that there are none of those portions which cannot be destroyed with impunity, by restraining gradu- ally the extent of the parts, to which the heart dis- tributes blood. He took a rabbit six weeks old, and after opening its abdomen, he tied the aorta, between the caeliac and anterior mesenteric ar- tery, after which he destroyed all the lumbar medulla. This rabbit was still perfectly alive, supporting itself on its fore paws, and supporting its head well more than half an hour afterwards, when the commission adjourned; whilst another rabbit, nearly of the same age, whose lumbar medulla had been destroyed without the aorta being tied, as a point of comparison, died in less than two minutes. 280 EXPERIMENTS ON THE Dr. Le Gallois afterwards performed the ex- periment of destroying the cervical medulla, the action of which upon the heart is more imme- diate, and much greater still than that of the lumbar medulla; he performed it upon rabbits five or six weeks old, without stopping circula- tion. He first decapitated the animal with the usual precautions; he then performed the pul- monary inflation during five minutes; after which he destroyed all the cervical medulla; he re- sumed the pulmonary inflation immediately af- terwards^ and the animal was left fully alive, and continued so as long as was thought fit to con- tinue the inflation. The same experiment was repeated, with the same success, upon two other rabbits of the same age. It was further performed upon one ot these, five minutes after having destroyed the cervical medulla, the author de- stroyed about the anterior third of the medulla dorsalis, then five minutes after the second third, and five minutes after the last third. Circulation and life continued after the destruction of the two first thirds, and only ceased after that of the last third. During this experiment, the inflation PRINCIPLE OF LIFE. 281 was only interrupted during the period neces- sary each time to destroy the medulla. These experiments led Dr. Le Gallois to ano- ther much more difficult, the object of which is to prove that, by confining by ligatures the circula- tion to those parts only corresponding with any one portion of the medulla, this portion of me- dulla supplies the breast with sufficient energy to keep up the circulation of those parts. He detruncated, by cutting off both extremities, a rabbit thirty days old; at one end, at the first lumbar vertebra, and at the other at the second cervical vertebra; then by inflation supported life in the chest of this rabbit thus separated. We shall not describe the mode of operation, because the author has explained it minutely in his memoir, we shall merely state that the ex- periment completely succeeded, though an ar- tery, that could not be tied, caused a pretty co- pious hemorrhage, and occasioned fears as to its success. Finally, Dr. Le Gallois produced the partial death of the hinder parts, in a rabbit about 2N £g£ EXPERIMENTS ON THE twelve days* old, by tying the aorta between the caeliac and anterior mesenteric arteries. Twelve minutes after, death appearing to be complete, he united the aorta, and life was re-established, by degrees* throughout the whole of the hind parts, so far that the animal could walk with ease. This partial resuschatiomf proves that a general one might likewise be produced, if it were possible to re-establish the circulation after the extinction of life throughout the whole of the spinal marrow. But the experiments of the au- thor demonstrate much better than had been done before, why the resuscitation of the whole body is impossible. The author also made, in our presence, ex periments on guinea-pigs, from whence it re- sults that in these animals, the power of the heart depends likewise upon the medulla spi- nalis; only a greater extent, than in rabbits of the same age, must be destroyed to stop the circulation. We shall terminate this account of the expe- riments which Dr. Le Gallois made in our pre- sence, by those made on cold-blooded animals, PRINCIPLE OF LIFE. 2Q3 the results.of which are enliirely opppsejlto those obtained, and to which so much value was at- tached by the most zealous partisans of Haller, and amongst others, Fontana (a). Tche author first opened the cranium, and then the t^or^x ,of a frog, and laid the heart bare; then he firmly tied the animal (b), and whilst one of us observed the motions of the heart w^th a watch, marking seconds, he destroyed the cerebrum, and all the medulla spinalis, by means of a probe, introduced through the opening of She cranium; the motions of the heart were instanta- neously stopped; they were only resumed a,few seconds after, and no longer observed the same harmony: they were more frequent than before the destruction of the medulla. The same expe- riment, made upon five frogs, was uniformly at- tended with'the same results. The motions of the heart were not suspended in all, during the same number of seconds, but the suspension was al- (a) Memoires sur les parties sensib. et irritab. torn. III. p. 331.—Traite sur le venin de la vipere, etc. Flo- rence, ,^781. Tpni. II. p. 16.9,171. (b) Ibid. p. 233, of the work first cited; and page 171 of the second. 284 EXPERIMENTS ON THE ways extremely well marked, as well as the change in the time of the pulsations. We shall add, that the amputation of the thighs in the frogs, whose medulla had just been destroyed, yielded no blood, and that the salamanders being decapitated after a like operation, did not bleed either, whilst in both these cases there was a hemorrhage, when the medulla spinalis was un- touched. These experiments appear to us completely to confirm all the consequences which the author had drawn from them, and with which he con- cludes his memoir. To confine ourselves to the principal points, we consider as fully demon- strated: 1st. That the principle of all inspiratory mo- tions, resides nearly in that part of the medulla oblongata, which gives rise to the nerves of the eighth pair. 2d. That the principle which animates every- part of the body, resides in that part of the me- PRINCIPLE OF LIFE. 285 dulla spinalis, from which the nerves of that part originate. 3d. That it is likewise from the medulla spi- nalis, that the heart receives the principle of its life, and of its power; but in the whole medulla, and not in a circumscribed portion of it alone. 4th. That the great sympathetic has its origin in the medulla spinalis, and that the peculiar character of this nerve is to place every one of the parts to which it is distributed, under the immediate influence of the whole nervous power. These results readily resolve all the difficulties that have arisen since the days of Haller, on the causes of the motions of the heart. It will be re- collected, that the principal consist in explain- ing, 1st. Why the heart receives nerves. 2d. Why it is submitted to the power of the passions. 3d. Why it is not to the will. 4th. Why circulation continues in the acephali, and in decapitated animals. It will be recollected also, that no ex- planation has hitherto been able to reconcile these points, or at least could only do it by hypotheses 285 EXPERIMENTS ON THE which, as we have before /obaeiwed, give rise to other difficulties. But it is now very readily conceived why the heart receives nerves, and why it is found so peculiarly submitted to the power of the passions, since it is animated by all the medulla spinalis. It does not obey the will, because all the organs which are under the influence of the whole of the nervous power are not submitted to it. Finally, circulation con- tinues in the acephali, and in decapitated animals, because the motions of the heart do not depend upon the brain, or only secondarily. It is our duty to remark, that this last point, on which Dr. Le Gallois has diffused so much light, pre- sents nothing but confusion and error in the authors both in the ancient and new Hallerian school; not one of them has distinguished the motions of the heart which take place after de- capitation, from those which are observed after the excision of that organ or after the destruction of the medulla spinalis; and they thought that both would be equally adequate to the main* tenance of circulation. But these motions are essentially different from each other. The latter have no power to maintain circulation; they PRINCIPLE OF LIFE. 287 are perfectly similar to* the weak motions which may be excited in- the other muscles for some time after death. Dr. Le Gallois designates them under the name of motions of irritability (mouve- ments d'irrhabilite), without attaching at present any other sense to that expression, than to ex- press what takes place in the dead body (phe- nomenes cadaveriques). The last task now devolves upon us, which is, to indicate what is the sole property of Dr. Le Gallois in the work which is the object of this report, and what share others might claim in it. We can affirm, without fear of contradiction, that all this work belongs to him; it is enough to read his memoir with attention to be con- vinced of it. Chance furnished him with the idea of his first experiment,, and that produced all the others; each of them having been sug- gested, and as it were, directed by the preceding one. Following then* step by step, we find that his own method was his only guide, and by which alone he was governed. It is an unex- ampled instance in physiology, to find a work 288 EXPERIMENTS ON THE so considerable, every part of which is so con- nected, and so dependent upon each other, that to arrive at the perfect explanation of a fact, it is necessary to re-ascend to all those by which the author has arrived at it; and that no one deduc- tion can be denied, without denying all the pre- ceding ones, or raising a doubt with respect to those which follow. It might have been expected, that, in re- searches so numerous, and which, by the im- portance of the questions they embrace, have arrested the attention of a great number of learn- ed men, the author would frequently have been induced, even by following his own method, to repeat experiments already known. Never- theless, out of all those recorded in his memoir, we have only remarked two that had been per- formed before him. One by Fontana, the other by Stenon. The first (a) consists in inflating and keeping alive an animal after decapitation. Fontana had only performed this experiment with a view of conveying oxygen to the venous (a) Traite sur le venin de la vipere, etc. torn. I. p. 317. PRINCIPLE OF LIFE. . 289 blood, and it is readily perceived that it was foreign to our object. As it was unconnected, and could not serve as a proof to any one point of doctrine, little attention was paid to it, and it was left confounded with many other facts, from which a glimpse had been perceived, that even warm-blooded animals can survive decapitation, without knowing in other respects what was the real source of their life in that state. Hence it remained nearly unknown, except in a few English and German schools, and Dr. Le Gal- tois himself was entirely ignorant of it, when he communicated his first researches upon the functions of the medulla spinalis to the Faculty of Medicine of Paris. In other respects, this ex- periment was only one of the means which Dr. Le Gallois used to demonstrate two of his principal discoveries, namely, that the principle of the inspiratory motions resides in the medulla oblongata, and that of the life of the trunk in the Spinal marrow. The experiment of Stenon is that by which a ligature is applied to the abdominal portion of the aorta, and afterwards loosened to de- 20 290 EXPERIMENTS ON THE monstrate that the interception of the circulation paralyzes the part in which it takes place, and that on the return of the blood, life is renewed. This experiment is well known, and has often been repeated. The authors who made it, in- tended to prove,—some, that the contraction of the muscles depends upon the action of the blood upon their fibres; others, that in every part sensibility depends upon the circulation; and in both questions it equally served to prove the affirmative and the negative, according to the mode in which it was performed. Thus when the aorta descendens itself was tied, sensation and motion quickly disappeared in the hinder parts (a). But when the ligature was made further on, only upon one of the crural arteries, although in this case circulation was entirely intercepted in the corresponding limb, sensation and motion were preserved for a long time (b). In this contra- diction ({ results, each author was satisfied with those which favoured his opinion, and he thought (a) Lorry, journal de med. an. 1757, p. 15. Haller Mem. sur le mouvement du sang. p. 203, exp. 52. (6)Schwenke, hoematol. p. 8. Les experiences 57 et 58 de Haller, loc. cit. p. 205. PRINCIPLE OF LIFE. 291 himself so much the more justified, as the true cause of this contradiction was not known. But in the hands of Dr. Le Gallois, this very experiment appears under a very different aspect, and assumes a decided character. It is clearly perceived, that if sensation or motion only cease in the posterior limbs when the ligature has been made upon the aorta, it is because it is in this case only that the circulation is intercepted in the portion of the medulla spinalis, which gives rise to the nerves of those limbs. Such, among the experiments of Dr. Le Gal- lois, are those alone which in our judgment might perhaps be claimed. But besides that the mode in which they make a part of his work, renders them his property, it appears to us that the novel point of view in which he has consi- dered them, the precision in the details, and the clearness in the results, which he has substituted to the doubt and obscurity hitherto presented, have given a new character to these experi- ments. 292 EXPERIMENTS ON THE We shall conclude with a few words respect- ing an opinion of M. Prochaska, which might be thought similar to that demonstrated by Dr. Le Gallois on the functions of the spinal mar- row. This author places the sensorium com- mune both in the brain and in the medulla spinalis at the same time (a); but it must be remarked, that he is of opinion that the nervous power is generated throughout the whole ex- tent of the nervous system, so that each part finds in its nerves, taken separately, the principle of its life and of its motions (b). He only con- siders the sensorium, as a central point where the nerves of sensation and of motion meet and communicate; and which establishes the rela- tions of the nervous parts of the body (c)\ whereas, Dr. Le Gallois'has demonstrated, that the spinal marrow is not only a means of com- munication between the different parts, but that it furnishes the principle of life and of energy which animates the whole body. And what (a) Opera minora, torn. II. p. 51. Marherr, Hartley, &c. were of the same opinion before him. (A) Ibid. p. 82. (c) Ibid p. 151. PRINCIPLE OF LIFE. 293 proves that Prochaska, in expressing his opinion (which, in other respects, he only gives as a probable (a) thing,) was very far from sus- pecting the true functions of the medulla spi- nalis, is that he only considers this medulla as a large bunch of nerves, crassus funis nerveus (b). In short, it appears to us that it may be said of the different authors, who had some notions of the subject treated by Dr. Le Gallois, what La Place so judiciously remarks on a similar occasion: " we may meet with a few truths, " but they are almost always mingled with so " many errors, and their discovery belongs to " him alone, who by separating them from the " mixture, succeeds in establishing them upon " a solid foundation by calculation and obser- " vations (c)." The opinion of your commissioners is, that the work of Dr. Le Gallois is one of the most (a) Opera minora, p. 153. (b) Ibid. p. 48. (c) Mem. sur l'adhesion des corps a la surface de* fluides dans la biblioth. britan. torn. XXXIV. p. 33. 294 EXPERIMENTS ON THE beautiful, and certainly the most important that has been produced in physiology, since the learned experiments of Haller;—that this work will constitute an epoch in this science, on which it must diffuse quite a new light; that its author, so modest, so laborious, so praiseworthy, de- serves that this class (of the Institute) should grant him its special benevolence, and also the encouragement which may be in its power. They should not forget adding, that the memoir they have just reviewed, is worthy of occupying a distinguished place in the recueil des savans Strangers, if the publication of the important discoveries which it contains, could be deferred till the period, perhaps too remote, of the publi- cation of that collection. (Signed) DE HUMBOLDT, HALLE, PERCY." The institute approves of the report and adopts its conclusions. * From the original, it would appear that M. Percy is the author of the above report. T. PRINCIPLE OF LIFE* 295 Resohed, Further,- that this report shall be printed in the history of this class, and that the committee of the class shall make arrangements with Dr. Le Gallois, for defraying the expences occasioned by the experiment which he has already made, and for the further continuance of them. A true copy. (Signed) G. CUVIER Perpetual Secretary. SUPPLEMENT, TO SERVE AS A FURTHER ILLUSTRATION OT OMISSIONS IN THE FOREGOING STATEMENTS OF EXPERIMENTS. ONE of the circumstances which have been found most prejudicial to the progress of ex- perimental physiology, is the slight attention, and I may almost say the absolute neglect, on the part of those who made them, in regard to the choice of animals. They were taken as they happened to be found, without distinction of species or of age, and the results of various ex- periments performed in this way, were com- pared as if they had all been made upon animals of the same species and age. I pursued a very different plan; although I performed mine on several species, I have more particularly con- fined myself to one, which I have selected as 2P 298 EXPERIMENTS ON THE the basis of all my researches. I preferred rab- bits, because these animals are easily managed in experiments; it is easy to procure a great number, and by raising them I might be per- fectly sure of their age; whilst it is very difficult to keep dogs and cats in sufficient number, and the age of those which are procured abroad is mosdy uncertain. Therefore I constandy made my first attempts upon rabbits, and upon them I made all the previous trials, through which I was obliged to go to ascertain the results. In this way, all my experiments may be compared with each other. The results being once ob- tained and fully ascertained, I had only to prove them on other species; and this is what I have done on dogs, cats, and guinea-pigs. To avoid all confusion, I have almost always spoken of rabbits in the two first sections. I advise those who wish to repeat my experiments, to begin by rendering themselves familiar with them, upon the same animals. Attention should be paid to choosing them of an age appropriate to the intended experi- ments. Whenever in any experiment rcspirtu PRINCIPLE OF LIPE. cjgp, tion or circulation is to be stopped, and that we may be enabled to observe the result of the differ- ent phenomena of life in either case, the age of the animals should not exceed ten days, that that these phenomena may last longer, and that more leisure may be obtained to observe them. Particular attention must be paid to this, when we wish to find in what part of the medulla oblongata, the primum mobile of respiration resides; or when we wish to compare the signs of life, in the two portions of a rabbit which has been divided transversely. It is further necessary that the animal should be very young, even when we wish to make only a transverse section of the medulla, with a view to ascertain the in- dependency in which the parts posterior to the section are to those which are anterior. In this experiment, when the animals are a little advanc- ed in age, and the section has been performed near the lumbar region, the palsy takes place in a very few minutes in the posterior parts, although life subsists in the posterior segment of the medulla; of which there is no doubt, since the circulation continues, and since it stops as soon as this segment is destroyed. It appears gQQ EXPERIMENTS ON THE that the palsy is produced by the circulation being very much weakened in the medulla, perhaps from the section of the superior and in- ferior spinal arteries (arteres spinales). What seems to render this probable is, that it hap- pens later if the medulla is separated nearer to the neck, and that in very young animals in which the circulation is very active, the palsy does not take place, or become observable, ex- cept for a long time after. The section of the medulla between the oc- ciput and the first vertebra, frequently pro- duces in rabbits mortal syncope. It is a singular feet, of which I shall in another place state the various circumstances; the safest way to avoid this accident, is to separate the medulla between the first and the second cervical vertebrae. When we wish to observe the effects pro- duced by the destruction of the whole or of part of the spinal marrow, care must be taken that such destruction be complete, which is not always easy, particularly in dogs and cats. It often happens that the instrument slides betweea PRINCIPLE OF LIFE. gQj the vertebral canal and the membranes lining it, and only bruises the medulla. That which is used is an iron probe, the diameter of which is proportioned to that of the vertebral canal, and consequently larger as the animal is older. I endeavour to introduce it within the mem- branes, and push it through the whole extent intended to be destroyed,—then I withdraw it; and I repeat these two motions several times, but with caution, lest I should introduce air into the vessels by lacerating them too rashly. Those parts which are most convenient for the introduction of the probe, and easiest to be dis- tinguished in the living animal, are at the occi- put, or between the two first cervical vertebrae, and between the last dorsal and the first lumbar vertebrae. The latter is easily known, when the skin has been divided longitudinally upon the spine and the ribs have been laid bare; it is the intervertebral space which is situated imme- diately below the last rib. Whatever portion of medulla I wish to destroy, it is always through one of these two places that I introduce the probe.- To destroy all the medulla, I introduce it through the first and then push it as far as 302 EXPERIMENTS ON THE the tail. When we only wish to destroy one of the three portions, the destruction of the lum- bar portion presents no difficulty; it is sufficient to introduce the probe between the last dorsal vertebra and the first lumbar, and to push it on even to the tail. But that of the cervical and dorsal portions requires some preliminary cau- tion, and can only be done with any degree of precision, when you know previously the usual lengths of those portions in an animal of the species and age of that on which you perform the experiment. The following are the usual length of those of the rabbits: Ages. Common Lengths Common Lengths of the of the Cervical Medulla. Dorsal Medulla. Days. Millim. Lines. Millim. Lines. 1 17 ( 7\) 33 ( 14|) 5 18 ( 8 ) 36 ( 16 ) 10 21 ( 9\) 44 ( 19|) 15 24 (101) 47 ( 21 ) 20 27 (12 ) .51 ( 22|) 25 29 (13 ) 56 ( 25 ) 30 34 (15 ) 65 ( 29 ) Measure with a compass the length of the por- tion to be destroyed, carry it on the probe, and mark it on it with a piece of thread, then push the PRINCIPLE OF LIFE. 3Q3 probe up to the thread, into the vertebral canal, beginning at the occiput, for the cervical medulla, and between the last dorsal and the first lumbar, for the destruction of the dorsal; then lay the nail of the index finger of the hand holding the probe on the thread to prevent its slipping, and, after the operation, compare the measure taken by the compass to be certain that it has not slipped. The experiment being terminated, the vertebral canal should be opened, to ascertain that the destruction of the medulla has been complete; scissors are sufficient for this purpose, in animals one month old, and even more. I always prefer one of the two hind members for amputation, to try whether there will be any hemorrhage; I amputate with scissors in the middle of the foot, of the leg, or of the thigh, ac- cording to the degree of force which the circu- lation appears to preserve; when I suppose it to be stopped, I begin by the amputation of the thigh. One of the operations which require the most habit in the above mentioned experiments, and that upon which the whole success of most of these experiments depend, is the inflation of 204 EXPERIMENTS ON THE the lungs (a). Whenever the brain can no longer act upon the inspiratory organs, whether the medulla oblongata has been disorganized, or the medulla spinalis divided or destroyed near its origin, if any other operation has been per- formed, the effects of which are intended to be observed, it is indispensable to blow air into the lungs, to try to prolong the life of the animal; otherwise it would be doubtful whether its death was produced by the operation or by the as- phyxia. It is often necessary to have recourse to this method, though the brain and the origin. of the medulla spinalis remain entire; this hap- (a) This operation has been erroneously designated by the name of Hook's experiment. Long before this Englishman, Vesalius* had made use of it, to protract life in animals whose breast he had opened with a view to observe the mouons of the heart. Among the authors who have afterwards repeated it with various views, Goodwint has, in a particular manner, the merit of having presented it, as the most powerful remedy against asphyxia; and it is upon this that I think my ex- periments will leave no doubt. * De human! corporis fabrica. Basilex. 1555, p. 824. f La connexion de la vie avec la respiration, traduit de 1'An- glais par M. Hall4. Paris, 1798. PRINCIPLE OF LIFE. 3qc pens when the animal has been much weakened, and has not preserved vigour enough to breathe. In this case the circulation still continues; but the asphyxia would soon make it cease. On this subject I would remark, that the weakest degree of action in the medulla spinalis that may be compatible with life, is that which maintains some remains of circulation. It is true that the degree necessary for the last inspirations of a dying animal is very nearly the same, yet it is always a litde stronger. In adult animals, the difference of these two degrees is not always easily distinguished; but it is very evident in very young animals. Therefore, when these are asphyxiated by intercepting the air, the inspira- tory efforts always end several minutes before the circulation, and they may always be recalled to life long after respiration has entirely ceased. The principal conditions to be effected in the inflation of the lungs are, to introduce into the lungs a quantity of air proportioned to their capacity, or rather to that which they receive in a natural state; to renew this air by every infla- tion, and to perform a number of them nearly 2Q gQg EXPERIMENTS ON THE equal to that of the natural inspiration, in a given time. The success depends, in a great measure, upon the instrument that is used; I choose a common pewter syringe, which has a hole at the bottom of the cylinder, and which is to be a litde larger than the orifice of the pipe; and besides the ring which terminates the handle of the piston, it has two more on the top of the body of the cylinder, one on each side. This is the only peculiarity. It is to be used thus: take it with the right hand, passing the index and ring finger into the rings of the cylinder, and the thumb into that of the piston; introduce the pipe in the opening previously made in the trachea, close to and behind the larynx; place the animal on its back, hold it by the head and neck, or if it has been decapitated by the neck and trachea, with the left hand, which is placed behind the index finger, which is brought back upon the trachea to fix the pipe, and retain the inflated air; then set the piston in motion, by alternately moving the thumb to and from the two other fingers (a). In these alternate motions, (a) See the plate. PRINCIPLE OF LIFE. 307 that the air may be regularly propelled into the lungs, thrown out and renewed, it is necessary to stop the hole which is at the bottom of the cylinder, with the thumb of the left hand, during two successive motions of the piston, one reject- ing, the other extracting; and to unstop the hole by removing the thumb in the two subsequent motions. Thus if, when the body of the syringe contains the quantity of air to be introduced into the lungs, the hole is stopped, and the piston pushed, this air passes into the chest; and if, whilst you continue to keep the hole stopped, the piston is withdrawn, the same air returns into the body of the syringe. These are the two first motions, or inspiration and expiration. Next to this, if you unstop the hole by removing the thumb, and you push the piston to the bot- tom of the syringe, this same air entirely escapes through the hole, meeting with less resistance than through the pipe; and if the hole remaining open, you draw the piston, fresh air enters. These are the two subsequent motions which EXPERIMENTS ON THE renew the air in the body of the sy. It is impossible to say what is the precise quantity of air that is suitable for each inflation: for if the quantity of a natural inspiration is so difficult to be determined in man, it is much more so in animals. All that can be done in this respect, is, to make a near guess. I have three syringes of different sizes, which are sufficient for all my experiments; and I employ any one of them, according to the age and the size of the animal. The following are their dimensions (b): Internal diameter. millim. line. 18 (8) 23 (\0\) 37 (16J) (a) The instrument used by Goodwin was also a sy- ringe, but, from an error, difficult to be explained, the hole intended for the renewal of the air, instead of being at the bottom of the cylinder, was about the superior third. In this way, the air could be renewed but very imperfectly. (A) The new French measures proceed in a decimal order; for instanee, the millimetre is the tenth part of 308 expel and ringe (a). Length measured outside. millim. The smallest, 77 inch. (2 line. 10) The middle? gl sized, 5 The largest, 92 (3 (3 ) 5) PRINCIPLE OF LIFE. 3Qp The small one answers for rabbits not older than twenty days; and it might even be used when older, if its capacity was not lessened by the whole volume of the piston. When rabbits are but a few days old, I confine the motion of the piston to two or three-twelfths of an inch, and increase it by degrees with the age of the animal. The small pewter syringes have the incon- venience, that the pipe is frequentiy too large for the trachea of new born rabbits, and especially for that of guinea-pigs. This may be remedied by a silver pipe fitted upon the pewter one. This pipe, which is very thin at the end, ought to the centimetre; the latter is the tenth part of the deci- metre, the decimetre is the tenth part of the metre, and so on. The numbers which are annexed to the following names of the French measures, express the number of English inches or Troy grains, to which they are equi- valent. Millimetre 0,039371 Eng. inch. Centimetre 0,39371 Decimetre 3,9371 Metre 39,371 The metre is equal to the forty-millionth part of the whole circumference of the earth. T. 310 EXPERIMENTS ON THE have a conical shape; and, in general, the pipes of all syringes intended for inflation, ought to be conical, and grow larger pretty quickly, that by pushing them in a suitable manner into the trachea they may completely fill it. I use the middle sized one for rabbits from the age of twenty days to that of two months and beyond, and I likewise vary the motion of the piston; this syringe is always sufficient for adult guinea-pigs. I only have recourse to the third for larger rabbits, or for those younger animals having more capacious lungs, such as dogs. Care must be taken that the piston perfectly fills the body of the syringe, and yet that its motion should be performed easily and without effort, other- wise inflation will be laborious, and cannot be continued for any length of time. Besides, the jirks occasioned by uneven motions would pro- duce some disorder in the lungs. As to the number of inflations to be made in a minute, it cannot entirely be assimilated PRINCIPLE OF LIFE, 311 to that of natural inspirations in rabbits and guinea-pigs, which are generally upwards of eighty per minute. There would be danger, in thus hurrying the inflations, that the vessels of the lungs would be ruptured, and the inflated air extravasated. I generally produce fifty per minute. The decapitation required in many experi- ments may be performed in several ways, which may be all reduced to tying the vessels of the neck before the head is separated, and to begin- ning the pulmonary inflation before the animal is killed by asphyxia. It must be recollected, that the asphxyxia begins when the medulla spinalis has been separated between the head and the origin of the phrenic nerves, and that the pulmonary inflation must be resorted to so much the more prompdy, as the animal is older. The safest way is, to be governed in that respect by the gapings; there is every reason to expect, that the inflation will succeed, when it is per- formed before they have ceased. If any circum- stance should prevent their being observed in an experiment, the period of their cessation may 312 EXPERIMENTS ON THE be calculated from the table of page 84. The pro- cess I have described, page 116-17, and 128-29, is specially suitable for rabbits advanced in age. They may be simplified for those which are less than a fortnight old, and which do not require so prompt a recourse to the pulmonary inflation. For these I use the following: The animal being placed on its belly, I hold him by the head with my left hand; I stretch the skin of the nape of the neck between my thumb and index finger of the same hand. I find out, with the index finger of the right hand, through the skin, what is the length of the interval between the first and second cervical vertebra;, and thrust into it a large sewing needle, which I take in the same hand, and with it I cut through the me- dulla. Then I turn the animal upon its back, and keep it so, still holding it with my left hand by the head, and by fastening to a nail driven on the table, the loop of a piece of twine previously tyed to its hind feet;—I take a scalpel with the right hand, and stretching the skin and the soft parts with my left thumb and index finger, I lay bare the trachea, and the vessels of the neck; I tie both carotids, and the external and internal PRINCIPLE OF LIFE. 313 jugular veins, by means of a common sewing needle with thread (a); I slide the scalpel under the larynx, to loosen it from the os hyoides; this being done, I leave the scalpel, and take scissors, with which I separate the neck near the occiput; and at is not till then I begin the inflation of the lungs. It often happens that a guggling noise is heard in the breast, as soon as decapitation has been performed. It is a sign that the air has penetrated the vessels; and the experiment has failed. If there be any difiiculty in finding the first cervical vertebra through the skin, they may be laid bare by a longitudinal incision. I prefer the needle to the scalpel, to divide the medulla spinalis, because it causes less hemor- rhage. In all the experiments, attention must be paid to the choice of the animals, which should be sound and in good health. If sick, and especially if cold has rendered them languid, the result (c) Needles, slightly crooked, would be more conve- nient; but I have given up using the common surgeon's needles, which are too sharp in their edges, because I have frequently cut through the arteries with them 2 R 314 EXPERIMENTS ON THE will not be the same, especially in what re- gards the duration of the phenomena. Cold modifies and protracts the phenomena of as- phyxia, in a very remarkable manner, in very young animals. This is a curious fact, capable of important applications to the human foetus; and connected with the theory of hibernation in certain animals. I barely mentioned it to the society of the Faculty of Medicine (a); I shall pursue the inquiry hereafter. If the eighth pair of nerves be divided in dogs newly born, that are benumbed with cold, the temperature of the atmosphere being ten degrees (Reaumur*), they may live a whole day in that state, without there being any necessity for making an opening into the trachea. This is owing to their glottis not closing so exactly as in cats, and the very small quantity of air, for which it may still leave a pas- sage, being sufficient for the maintenance of so weak an existence. (a) Bulletin de la Faculte de medecine de Paris, 1812. No. l. * Ten degrees of Reaumur's thermometer are equal to fifty-five of Farenheit's. PRINCIPLE OF LIFE. 315 When the eighth pair is divided in guinea- pigs and an opening is made into the trachea, this canal being very narrow in these ani- mals, it is very difficult to prevent its being stopped. Continual attention should be paid to this. I have said, that the degree of fulness of the carotids was a sign equally certain and con- venient, to judge of the state of the circulation; and that their vacuity always indicates that this function had ceased. But it sometimes happened, that these arteries still contain a small stream of blood, and that they are more or less round, though the circulation be stopped. To prove the correctness of this fact, it is enough to lay bare one of the carotids through a certain ex- tent, and to press it with the end of the finger, moving from the breast towards the head. If, when the finger is taken off, it remains white and flat, as if only a little blood comes from the head, there is no doubt that the circulation is stopped; for when it is going on, even in the smallest degree, the blood often returns in the carotids thus emptied, upon the finger being 31 ft EXPERIMENTS, &c. taken off; it returns from the heart, and by thus trying it several times the result proves always the same. When the circulation has been weakened by the destruction of a portion of the medulla spi- nalis, or by any other cause, the degree of pres- sure necessary to flatten the carotids at any spot, sufficiently indicates that degree of weak- ness. In health, if you press this artery with a probe, it requires a certain strength to flatten it, and that only takes place in the spot pressed; if it be raised by a probe passed underneath, it still retains a cylindrical form, unless raised very high. But when the circulation is weakened, one moderate pressure is enough to depress this artery, not only in the place compressed, but at a greater or less distance on both sides, before and behind; and by raising it with the probe, it is flattened upon this instrument, and beyond on each side. The degree of weak- ness of the circulation may thus be estimated and compared, in the different cases, by the fa- cility and extent of the flattening of the carotids. END OF THE EXPERIMENTS. 317 NOTE RESPECTING THE TEETH OF RABBITS AND GUINEA-PIGS. I HAVE ascertained, by repeated observations, made on rabbits and guinea-pigs of every age, that these animals have no milk teeth, and that they preserve, during all their lives, those which appear before or after birth. In the young animals, the teeth arc slightly conical, or truncated pyramids, so that in proportion as the edge is worn down, the part that advances from the socket, being gradually larger, and this continuing till the animal acquires nearly its full growth, they assume a prismatic form. This fact indicates pretty clearly the final cause of the shedding of teeth in the species which are liable to it. It is at present fully proved, that teeth are substances formed by excretion, and not growing by intussusception, or continuing for ever in the state they were in when issuing from the socket. In this state of things, those which fill the alveolar arch of a young animal, and 318 which are fitted to the dimension of its jaws would no longer be so in the same animal when adult; more especially in the carnivorous, the teeth of which do not wear out nor grow from the mo- ment of their being fully out. To remedy the in- conveniences of stationary teeth in jaws which continue to grow in all directions, nature employs two methods; namely, the replacing of the first teeth, and the appearance of a second set at a more advanced period. But it is evident, that in animals, such as the rabbit and the guinea-pig, the teeth of which continually grow and become larger as they wear out at the edge, the teeth and jaws were to be left in the same proportion at every age, and that the shedding was useless; and it does not, in fact, take place. We may account from the same principle for the nails and several other bodies of this nature, which, like the teeth, being sub- stances formed by excretion, are not shed to be afterwards replaced. I have always observed that rabbits have six molar teeth on each side of the upper jaw, and not five only, as in the lower. The sixth and posterior one is very small, and 319 it is no doubt for this reason it had escaped the notice of zoologists. NOTE RESPECTING THE DURATION OF GESTATION IN GUINEA-PIGS. Guinea-pigs have been so long since na- turalized and multiplied in Europe, that it must appear strange that no author has been ac- quainted with the true duration of gestation in these animals. Buffon says it lasts three weeks; the new dictionary of natural history repeated the same opinion; others have assigned different durations, but they were equally erroneous. The cause of this uncertainty is due to the difficulty of ascertaining the moment of copulation, it being difficult for the male to effect it. It often takes him a fortnight, and sometimes more. During all this time, his apparent ardour and all his efforts are baffled by a singular disposition of the vagina of the female. This disposition consists in this, that the exterior orifice is glued and completely closed. The male must unglue 320 it before copulation takes place; it is then glued again three days after, and likewise glued again after parturition. It was by separating the females from the males upon perceiving the separation of the parts, that I found the duration of gesta- tion to be sixty-five days. But this happy pri- vilege of being for ever a virgin after numerous parturition does not belong exclusively to the female of the guinea-pig; it is also the privilege of an ancient inhabitant of Europe—the mouse. NOTE RESPECTING THE RELAXATION OF THE SYMPHYSIS OF THE PELVIS IN GUINEA-PIGS AT THE PERIOD OF PARTURITION. It is known, that in the animated discussions which have arisen concerning the section of the symphysis pubis in certain cases of difficult parturition, the partisans of this operation have grounded the principal hope of success on the swelling and relaxation of all the symphysis of the pelvis towards the end of gestation. They considered this swelling as a mode employed 321 by nature to increase the diameters of the pelvis, an indication to increase them still more by the artificial separation of the symphysis, and the possibility of obtaining a sufficient distance be- tween the two ossa pubis, on account of the hinge-like motion, which may be promoted by the sacro-Uiac symphysis thus infiltrated and softened. But while their opponents denied this swejling and its consequences, it does not ap- pear that any one has ever discovered a case in which nature herself performs a true and com- plete separation of the ossa pubis in order to render the delivery possible. This is never- theless what is observed in one species of ani- mals—the guinea-pig. When we compare the pelvis of the female of a guinea-pig, with the head of a full grown foetus, we are convinced, on the first view, that it would be utterly impossible that its head should come through the pelvis, and conse- quendy that the delivery should take place, if the pelvis constantly preserved the state and dimensions observable at any other time than at that of gestation. Without going at present into 2S 322 any further details concerning the respective di- mensions of the head of the foetus and the pelvis of the female of that species, suffice it to remark, that parturition depends especially upon the transverse diameter of both. Now, the trans- verse diameter of the head of a foetus of mid- dling size full grown, but dried, is nine twelfths of an inch (French measure); whilst that of the pelvis of a female of middling size, measured between the acetabula on the bare and dried bones, is not quite five twelfths of an inch. If we take in the account t,he soft parts lining the cavity of the pelvis, we shall find that when alive its diameter is about one half of the head of a foetus; and nevertheless guinea-pigs arc delivered with much ease. It thence necessarily follows, that nature must have provided some means of removing the difficulty produced by this enormous disproportion. And this is what does in fact take place. I indicated in 1809 (see preceding note), that the duration of gestation in these animals, was sixty-five days. About three weeks before de- livery, the symphysis pubis is seen to acquire 323 more thickness and a slight mobility; these are continually increasing. Eight or ten days be- fore delivery, the two ossa pubis begin to sepa- rate from one another. This separation increases slowly at first, and only begins to go on rapidly for the three or four days which precede the delivery. It is such at the moment of parturi- tion that it readily admits the middle finger, and even sometimes both the middle and fore finger together. The delivery being at an end, the bones of the pubis soon close. Twelve hours after, the distance of the separation has lessened more than one half; and twenty-four hours after, they are in contact at their anterior extremity; and in less than three days, they are perfectly so through the whole extent of their symphysis, which then only presents a slight thickness and mobility. A few days after, nothing is to be seen but a very slight mobility, which dfsap- pears sooner or later. But when the females are old or sick, the re-union is made more slowly. 324 I have measured the separation of the pubes in three females killed at the period of their delivery. In two, which were at the sixty-fourth day of gestation, this separation was about five twelfth parts of an inch; and in a third, which was at the sixty-fifth day, the separation was a little less than six. In these three females the sacro-Uiac symphysis possessed great mobility but without any remarkable separation. This mobility of the sacro-Uiac symphysis, without which the separation of the ossa pubis could only be very limited, allows besides, a posterior motion of the os sacrum; and as it is only the posterior extremity of the os sacrum which corresponds with the symphysis of the ossa pubis, it is perceived on the one hand that the head of the foetus, by pressing upon this extre- mity, acts upon the sacro-iliac symphysis as it would upon the end of a pretty long lever; and on the other hand that a light motion of the sacrum or of the ossa innominata in the two symphysis, is adequate to produce a sufficient separation be- tween the posterior extremity of the os sacrum and the symphysis of the ossa pubis. 325 From this statement, it appears that the pelvis of the female of tii*- guinea-pig, is considerably increased in all its diameter at the moment of parturition. Nothing less than such a median* ism was required, that so small an animal might bring forth foetuses at least as large as those of the rabbit, and which are besides nearly in an adult state. For little guinea-pigs are seen to run almost as soon as they are born; both their eye-lids and ears are opened; all their teeth are out, and they can chew grass on the day of their birth: scarcely do they want to suck, and they might in a warmer climate than ours entirely do without their mother. In short, that which proves perhaps better than any thing else how far they are grown at the moment of their birth is, that they then suffer from asphyxia, in the same manner as other animals do at nearly an adult age. From my experiments, the asphyxia which rabbits can bear is about seven times longer at the moment of birth than at the adult age; it is nearly the same with dogs and cats; whereas the new born guinea-pig can only bear one which is scarcely double of that supported by the adult. Thus the duration of gestation, 326 which in general is shorter in proportion as the animals are smaller, is twice as long, and even a little more, in the guinea-pig than in the rab- bit. But these are not the only anomalies which we meet with in these extraordinary animals; I shall point out others hereafter. THE END. EXPLANATION OF THE PLATE. Fig. I. Represents the smallest of the three syringes mentioned in page 308. The tube a is truncated and lined with tow for the in- sertion of a silver one, represented by d. ccc, Are ribbons destined to be bound round the rings of the syringe, so that the metal should not hurt the fin- gers 'if the operator. Fig. II. Represents the middling-sized syringe; the tube is screwed at a, which gives the facility of changing it when it is found to be too small, and to substitute another which fills up entirely the trachea of the ani- mal. The tube of the large syringe can also be taken off. ccc, Knot made at the two ends of the ribbon, bound round each ring. In those two figures, b indicates the hole made at the bottom of the body of the pump, to renew the air. Fig. III. Represents a decapitated rabbit, kept alive by pulmonary inflation, performed with the small syringe to which the silver tube is adapted. See page 306 & 312. The thumb of the left hand stops up the hole of the syringe, so that the operator may perform with ease. This hole must correspond to the middle of the inter- val, which separates the two rings from the body of the pump. The animal is placed on a board, and has its two hind paws tied to a nail driven in the board. Its head is seen laying on the table, still continuing to gape; near it lays the needle threaded which was used to tie the vessels; at the end of the table are a scalpel, a pair of scissors, a large needle to divide the spinal marrow, and a watch, that the operator ought always to have before his eyes, to indicate the length of time the experiment lasts, and particularly the period when he is to commence pulmonary inflation, and the time he may desist without danger. If to these instruments 328 we add a small piece of iron wire, to clear the tube of the blood and mucus which sometimes obstruct it, a few iron probes of various sizes to destroy the spinal marrow, a compass and a foot-rule to mark on the probe the length of the portion of spinal marrow that is to be destroyed (see page 302), we hall have every thing that is necessary to repeat all the experiments mentioned in the course of this work. ERRATA. Page 48, line 24, read the phrase thus,—And if in this half only a part of the spinal marrow be destroyed, all the parts which receive their nerves from this part are instantaneously struck with death while the remainder of the half continues alive. Page 50, line 3, for breast, read thorax. 65, 22, vertebra, vertebra. feeling, sensibility, carotid, carotids. two minutes and a quarter, read in about tvso minutes and a quarter after. vertebrae, read vertebra. breast, chest. breast, thorax. physiology, in the physiology. takes, take. in the, on the. sawoages, Sauvages's. such portion, suck a portion. Pages 131,132, and 148, for resurrection, read resuscitation 95, 13, 103, 8, 114, 3, 128, 24, 129, 14, 129, 19, 165, 29, 204, 20, 205, 8, 205, note, 1, 266, 14, k Mtd.Hist 3.70 I«I 3 c-\ 23: te? Tito Br ^*Wr*S If? ^rSjjj