7 ^ / AN EXPERIMENTAL INQUIRY INTO THE LAWS OF THE VITAL FUNCTIONS, ) WITH SOME OBSERVATIONS ON THE NATURE AND TREATMENT OF INTERNAL DISEASES; BY A. P. WILSON PHILIP, M.D. F.R.S.E. Fellow of the College of Physicians of Edinburgh, SJc. IN PAR T RE-P UBLISHED, BY PERMISSION of the PRESIDENT of the ROYAL SOCIETY, FROM THE PHILOSOPHICAL TRANSACTIONS OF 1815 & 1817, WITH THE REPORT OF THE NATIONAL INSTITUTE OF FRANCE ON THE EXPERIMENTS OF M. LE GALLOIS, AND OBSERVATIONS ON THAT REPORT. V PHILADELPHIA: PUBLISHED BY EDWARD & RICHARD PARKER, NO. 178, MARKET STREET. T. It. A. SKERRETT, PRINTER. 1 ¥ts7 CONTENTS. Preface.....Page vii An Experimental Inquiry, 8[c. PART I. Of the state of our knowledge respecting the principle on which the action of the heart and blood vessels depends, and the relation which subsists between them and the nerv- ous system ..... 1 CHAP. I. The Report made to the Class of Physical and Mathematical Sciences of the Imperial Institute of France on the work of M. le Gallois, entitled, Experiences sur le Prin- cipe de la vie, notamment sur celui des mouvemens du cceur, et sur le siege de ce principe ...... 2 CHAP. II. Observations on the foregoing Report . 51 IV PART II. Experiments made with a view to ascertain the laws of the vital functions . . 64 CHAP. I. On the principle on which the action of the heart and vessels of circulation depends 66 CHAP. II. On the relation which subsists between the heart and vessels of circulation, and the nervous system .... 76 CHAP. III. On the principle on which the action of the muscles of voluntary motion depends, and the relation which they bear to the nervous system ...... 94 CHAP. IV. On the comparative effects of stimuli appli- ed to the brain and spinal marrow on the heart and muscles of voluntary motion 100 CHAP. V. On the principle on which the action of the vessels of secretion depends, and the re- lation which they bear to the nervous sys- tem . ... . . 113 SECT. I. On the effect of withdrawing the nervous influence from secreting surfaces . 114 V SECT. II. On the nature of the nervous influence 119 SECT. III. Inferences from the preceding Sections 134 CHAP. VI. On the principle on which the action of the alimentary canal depends; with some ob- servations on an opinion of Mr. Hunter. 138 CHAP. VII. On the relation which the alimentary canal bears to the nervous system . . 147 SECT. I. On the process of Digestion. . . 149 SECT. II. On the effects on the stomach and lungs of destroying certain portions of the spinal marrow, compared with those of dividing one or both of the eighth pair of nerves 163 CHAP. VIII. On the cause of Animal Temperature . 175 CHAP. IX. On the use of the Ganglions . . 185 CHAP. X. On the relation which the different functions of the animal body bear to each other, and the order in which they cease in dying 2QQ 2 VI CHAP. XI. A review of the inferences from the preced- ing experiments and observations . 234 CHAP. XII. On the application of the foregoing experi- ments and observations to explain the na- ture and improve the treatment of diseases 249 Of Sanguineous Apoplexy . . . 252 Of Inflammation .... 258 Of JSTervous Apoplexy .... 288 Of Affections of the Spinal Marrow . 299 Of Asthma and Dyspepsia . . . 303 Of Suspended Animation . . . 328 Of Sympathy.....330 Appendix......333 PREFACE. THE obscurity of the nature of Internal Dis- eases, of which physicians have always complain- ed, seems to arise from several causes; the diffi- culty in those diseases of referring the painful feeling to the seat of the injury, proceeding from the indistinctness with which we refer to internal parts, and other parts sympathising with the part affected ; the deficiency of our knowledge of mor- bid anatomy, in consequence of which we are not always enabled from the train of symptoms to infer the derangement of structure ; our ignorance of the function of many internal parts, and where we have a knowledge of the function, our igno- rance of the principle on which it depends. If such be the causes of the obscurity of the nature of Internal Diseases, we may easily perceive the objects which ought to be kept in view in our en- deavours to obtain a more correct knowledge of them, and consequently of the means of cure adapted to them. By the frequent inspection of dead bodies, we learn to connect particular trains of symptoms with the changes of structure which occasion them, for although the sensations of which the patient complains are often ill defined, and sometimes not viii referred to the seat of the morbid action, yet the same morbid action almost always produces nearly the same train of symptoms. Nothing appears more to have retarded the progress of medical knowledge, than the obstacles which have in all ages been opposed to the inspection of dead bo- dies. The great importance of the information thus obtained, however, has been slowly recon- ciling the public mind to it; and we may with confidence anticipate the greatest improvements from the increasing frequency of this practice; without which we can no more acquire a know- ledge of the diseased states of the body, than we can of its healthy state without the aid of anatomy. But neither anatomy nor the inspection of mor- bid bodies can teach us the nature of the functions. A knowledge of them can only be acquired by comparing the structure of the organs with the actions observed in them while their vital power remains. Some of these actions are the objects of simple observation in our own bodies and those of other animals. Anatomy, for example, teaches us the structure, position, and attachments of the muscles; observation readily points out their func- tion, and by the lesion of this function we judge of the extent and degree of their morbid affec- tions, and are consequently guided in the appli- cation of our remedies. But there are other and more important functions, which in the entire ani- mal are hidden from our view. To ascertain ix their nature, experiments must be made on the liv- ing and newly-dead animal. We shall find that many parts retain their vital actions for a certain time after what we call death. To the aversion to experiments on living ani- mals, which every man must feel, we may, I think, in a great measure, ascribe the little pro- gress which has been made in this essential branch of medicine. Something too must be as^- cribed to the obscurity of the subject. The inter- nal functions of animals are of a nature so differ- ent from any thing which we are accustomed to see around us, that our previous experience gives Us little assistance in attempting to trace their laws, and our progress is necessarily slow and difficult. Hence it appears to have been that the earlier Physiologists, disgusted with the task placed before them, evaded it; and endeavoured by ingenious fictions to deceive their readers. It is uow universally agreed that if any progress can be made in Physiology, it is not by the wander- ings of fancy, but by patience and by labour. We are amused with the reveries of Stahl, but for instruction we look to the experiments of Haller. And to similar experiments we must look for all the information we can obtain on this subject. The hope of adding something to our knowledge of the vital functions, and thus improving the treatment of their diseases, induced the author to undertake the following Inquiry. X From the foregoing view of the subject it will be admitted, I think, that few writers have stronger claims on the indulgence of the public than the Physiologist, provided his endeavours are ration- ally directed. The knowledge, which it is his aim to acquire and communicate, is of the most important kind, while his means of information are always laborious, and of ten of a painful na- ture. These claims are increased by the circum- stances in which h« is usually placed. No per- son is fitted for physiological inquiries who has not obtained a competent knowledge of the differ- ent branches of Medicine. This knowledge is acquired with so much difficulty, and depends so' much on actual observation, that few who do not practice medicine as a profession ever acquire it. The Physiologist, therefore, generally pursues his inquiries amidst anxious and fatiguing engage- ments of a different kind, and of such a nature that all others must give place to them. I do not mention these circumstances as affording any apology for inaccuracy in points of consequence, because the writer owes it to the public to with- hold his communications till he thinks himself as- sured of their accuracy; but they may, I hope, be admitted as an apology for less important er- rors. The errors of the following Inquiry are not those of precipitation. It is above fifteen years since some of the experiments which I am about to relate, and many connected with them, were xi made. None have been made within the last year, during which I have employed the time I could allot to such engagements in arranging my experiments, comparing them together, and en- deavouring to guard against hasty inferences, which it is difficult to do at the time the experi- ments are made. I have endeavoured as much as possible to avoid experiments on living animals. Most of those related in the following Inquiry were made on the newly-dead animal; and it will appear, I think, from what I am about to lay before the reader, that for many experiments, for which the living animal has been thought necessary, the newly-dead animal may be used with equal, and sometimes with greater advantage. When it was necessary to experiment on the living animal, I uniformly observed the following rules; to de- stroy the sensibility previous to the experiment, when this could be done without influencing the result; when several animals were equally fit for the experiment, to choose the one which would suffer least from it; when there were several ways of performing the experiment, to choose the way which would occasion least suffering; if the ex- periment was necessarily fatal, to destroy the animal as soon as the purpose in view was an- swered ; and to take such precautions as rendered as few repetitions as possible requisite. xii I have been much indebted in making the ex- periments to the kind assistance of several gen- tlemen; particularly Mr. Hastings, late House Surgeon to the Worcester Infirmary, Mr. Shep- pard, Surgeon in Worcester, and Mr. Herbert Cole, successor to Mr. Hastings. I shall fre- quently have occasion to mention those gentlemen. AN EXPERIMENTAL INQUIRY, THE following Treatise is divided into two Parts. In the first Part I shall make the reader acquainted with the state of our knowledge respecting the principle on which the action of the heart and blood vessels depends, and the relation which subsists between them and the nervous system, at the time my experiments were begun; as on this, all our knowledge of the vital functions more or less immediately de- pends. In the second, I shall relate these ex- periments, and point out the inferences to which they seem to lead. PART I. Of the state of our knowledge respecting the principle on which the action of the heart and blood vessels depends, and the relation which subsists between them and the nervous system. The object of this Part cannot I think be better accomplished than by laying bejbre the 3 2 reader a translation of the Report of the Com- mittee of the National Institute of France, on the Experiments of M. le Gallois, and such ob- servations on it as it appears to demand. 1 CHAP. I. The Report made to the Class of Physical and Mathematical Sciences of the Imperial Insti- tute of France on the work of M. le Gallois, entitled Experiences sur le Principe de la vie, notamment sur celui des mouvemens du cceur et sur le siege de ce Principe. The Class having charged M. de Humboldt, M. Halle and me,* to make a report to it on the Memoir read at a meeting of the 3d of June last, by M. le Gallois, Doctor of Medicine, respecting the nature of the power of the heart, and whence it derives its power,f we are about to present to it a detail which will, perhaps, be as long as the Memoir itself, because with- out the necessary details and explanations it * M. Percy. t" Concernant le principe des forces du cceur, et le siege de ce principe." 3 would be impossible to appreciate all the merit of this excellent work. It was not till after the circulation of the blood was discovered by Harvey, early in the seventeenth century, that Physiologists turned their attention to the cause and mechanism of the movements of the heart, which have, since that time, given rise to so many different sys- tems. We shall not speak of those of Descartes,* of Sylvius de le Boe,t of Borelli.J They are very absurd, and serve only to prove how unfortu- nate were the first attempts to explain one of the most important functions of the animal CBConomy. We shall begin with the distinction which Willis first pointed out between the nerves destined for the voluntary, and those for the involuntary motions. He placed the origin of the latter in the cerebellum, of the former in the brain, properly so called. He taught that the motions of the heart, and other vital organs, experience no interruption, be- cause the cerebellum is in a state of constant * L'homme de Rene Descartes, et la formation du foetus avec les remarques de Louis Laforgue, Paris, 1677, p. 4 and 106. t Francisci De la Boe Sylvii Opera Medica Genevse, 1681, p. 5, 27, 28, 33, 475. J Joh. Alph. Borelli de motu animalium. Hagse Comitum, 1743, p. 89—92. 4 activity; but that the organs of voluntary mo- tion, on the contrary, require repose, because the brain acts only by intervals.* This dis- tinction of Willis was very generally admitted till the middle of the last century. It was chiefly with a view to it that* the division of the eighth pair of nerves, from which it was main- tained that almost all the nerves of the heart proceed, was performed in different countries. The object was to prove that it is from the cerebellum that the heart derives all its power, and it was alledged that the animal died in this experiment, in consequence of the communica- tion between these organs being interrupted.— But, besides that it dies too slowly to permit us to ascribe its death to this cause, it has been proved in later times by several Philosophers, and particularly by M. le Gallois, in a memoir which the Class ordered to be inserted in the transactions of learned correspondents, that death here proceeds from quite a different cause. It has sometimes happened, indeed, that animals have died almost suddenly after the division of the nerves in question, and the partizans of Willis have not failed to lay much stress on this circumstance, of which their ad- versaries could give no satisfactory explanation. * Tho. Willis opera omnia, edente Ger. Balsio Amstelo- dami, 1682, Tern. 1, de cerebri anatome, cap. xv. p. 50 5 But M. le Gallois has demonstrated in. the me- moir to which we have just alluded, that sudden death in this case only happens in certain kinds of animals, and in these only when they are very young, and that it is the effect of suffoca- tion,* more or less complete from the shutting of the glottis. There is nothing then in these facts in favour of Willis, to which we may add, that the eighth pair of nerves does not arise from the cerebellum, and that most of the nerves of the heart do not belong to this pair. Boerhaave was of the same opinion with Willis, but besides the nervous influence, he admitted two other causes of the motions of the heart; the action of the blood of the coro- nary arteries on its fibres, and of the venous blood on the surface of its cavities. Accord- ing to him the concurrence of these three causes produces the systole, and the simultane- ous interruption of their action in consequence of the systole gives rise "to the diastole, during which their action is renewed, f But this ex- planation, with the exception of what regards the stimulus of the blood on the internal sur- face of the heart, is contradicted by fact, which * Asphixie. This I translate suffocation, because we use the term Asphixia in a very different sense. Culleni Synop- sis Nos. Method. Gen. 44. t Her. Boerhaave Instit. Medicse, § 409.—Vanswieten in Aphorismos, &c. Lugduni Batav. 1745, Tom. 2, p. 18. 6 has not prevented its reception in the schools, with another error that has made no less noise. We allude to Stahl, and his soul or Archseus, which, regulating all the movements of the living body, subjecting them to the will, or rendering them independent of it, according as they are merely useful, or absolutely neces- sary to life, presides above all over those of the heart, and, through the influence of the nerves, insures their continuance; a species of reverie which is inconsistent with all the true principles of Physiology. After all, where would the Stahlians place this simple and indivisible being? In the brain without doubt. But then how does it happen that an animal may live, and the mo- tion of its heart continue after it is decapitated. Would they place it in the heart itself? But all animals, and especially those of cold blood, live a longer or shorter time after the heart is out out.* Other writers, such as Abraham Eus,f Stce- helin,J &c. have also endeavoured to explain the motions of the heart; but their systems, * For an exposition and refutation of this system see Haller's Element. Physiolog. Tom. 1, p. 480—8, and Tom. 4, p. 517—34. t Dissertatio Physiol, de causa vices cordis alternas pro- ducente. Lugd. Batav. 1745. \ Dissertatio de pulsibus. Basilese, 1749*. 7 almost as soon forgotten as conceived, do not de- serve to detain us. Those of Boerhaave and Stahl reigned almost alone, when in 1752 Haller published his ex- periments on irritability. These experiments and those of his followers tend to prove, that the contractile power belongs essentially to the muscular fibre. That property which Haller sometimes speaks of under the name of vis insita, sometimes after Glisson, under that of irritability, is the source of all the motions which take place in the animal; but it cannot produce them except some cause, some stimulus determines it to act. Thus all muscular motion implies two things, the irritability which pro- duces the contraction of the muscle, and the stimulus which determines the irritability to act. The irritability is every where the same. It only varies in intensity in the different mus- cles ; but it does not obey the same stimuli in all the muscles. The nervous power is the natural stimulus to all those which are under the influence of the will; and it is by exciting or suspending the action of that power on the irritability of such or such muscles, that the will causes any particular part to act or to be at rest. It is not thus with the muscles of invo- luntary motion; these are affected by stimuli of different kinds, which are appropriated to their different functions? and altogether different 8 from the nervous power. It is the blood which is the natural stimulus of the irritability of the heart: alimentary substances, of that of the intestinal canal, &c. We easily deduce from these principles the explanation of the leading circumstances which we observe in the motions of the heart. Thus its motions are involuntary, because they are independent of the nervous system; they take place without interruption during life, because the irritability which produces them belongs essentially to the fibres of the heart, and the blood which excites them is constantly supplied to this organ by the veins as it is carried off by hhe arteries. The systole and diastole suc- ceed each other alternately and regularly, because the stimulus of the blood always oc- casions the former both in the auricles and ventricles, and the systole itself, by expelling the stimulus, occasions the diastole, which re- news the systole by allowing access to new blood. Such is a summary view of the celebrated Hallerian theory of irritability. That theory was not contrived in the closet like the others of which we have spoken: it was founded, as we have said, on experiments made by Haller himself, and by the most distinguished of his scholars, who then occupied, or have since occupied, the first rank among the Anatomists 9 and Physicians of the last age. These experi- ments, repeated throughout Europe, found al- most every where supporters; but they found also some opponents of the greatest reputation. The principal cause of this difference of opinion, and that respecting which authors have not yet been able to come to any agreement, is the ques- tion, whether the motions of the heart are really independent of the nervous system. We may reduce to three heads the facts by which the school of Haller has supported the affirmative. 1st. If we interrupt all communi- cation between the heart and the brain, the only source of nervous power, by dividing the nerves which go to the heart, the spinal mar- row in the neck, or even by decapitation, the motions of the heart continue as before. 2d. If we cut out the heart of a living animal, and place it on a table, it continues to beat, a^d sometimes for a long time. M. de Humboldt has shewn that it beats more strongly, and for a longer time, when it is suspended. 3d. We always produce convulsions, even for some time after death, in the muscles of voluntary motion, by irritating their nerves, either mechanically or in any other way. On the contrary, the irrita- tion of the cardiac nerves occasions no change in the motions of the heart, nor re-calls them when they have ceased. The same observation is true of the medulla oblongata and spinal 4 10 marrow, the irritation of which occasions strong general convulsions, but produces no effect upon the heart. These facts are correct, except perhaps those of the third head, respecting which there is some difference of opinion. For in admitting them, the adversaries of irritability have asked, why, if the nervous power has no action on the heart, is this organ supplied with nerves, and why is it so evidently subjected to the influence of the passions ? Haller never gave any satisfac- tory explanation of these objections, but every thing proves that he felt all their force. When we read with attention all that he has said of the motions of the heart, in his dissertations on irritability,* and above all in his great work on Physiology,! we are struck with the contradictions which we meet with in them, and which makes the perusal of them fatiguing.— Through all of them his great object is to prove, that the motions of the heart are inde- pendent of the nervous system. All the facts, all the experiments, all the observations which he brings forward, tend to this end; and yet he seems to admit in several places that the nerves possess an influence over the heart.— * Memoires sur la nature sensible et irritable des parties, etc. Lausanne, 1756.—Opera minora, Tom. 1. t Element. Physiol, lib. iv. sect. 5, et lib. xi. sect. 3. 11 It is true that it is with an air of doubt that he admits it, and confines himself to saying, that it is possible, that it is not unlikely, that the heart derives a power of motion from the nerves.* These contradictions with which se- veral justly celebrated writers have reproach- ed him, amongst others MM. Prochaska,f Behrends,^ Ernest Platner,§> &c. proceed evi- dently from his not being able to reconcile the results of experiments with the influence of the nervous power over the motions of the heart; and, in rejecting this influence, finding it impossible to explain the use of the cardiac nerves and the effect of the passions on the heart. Here is the great difficulty in the con- troversy of which we speak. Those who, like Fontana, formally rejected all intervention of the nervous influence, have been forced to admit that the nerves, destined to convey to every other part, life, feeling and motion, have no known use in the heart. || * Ibid. lib. iv. sect. 5, p. 493, et alibi passim. t Opera minora Viennee, 1800, Tom. II. p. 90. 1 Vol. 3, p. 4, of the Collection of Ludwig, entitled Scriptores neurolog. minores selecti, Lipsise, 1791—5. Four volumes, in 4to. § Vol. 2, p. 266, of the same Collection. || Memoires sur les parties sensibl. et irritab. Tom. 3, p. 234. See also Caldani, ib. p. 471, and Le Traite sur le venin de la vipere, Tom. II. p. 169—171. 12 Such consequences evidently disclose the in- sufficiency of the theory of Haller, and seve- ral of his followers have acknowledged the necessity of some modification of it, and admit the nervous power to be one of the principles on which irritability depends. They are thus enabled to assign a use to the nerves of the heart, and to explain the influence of the pas- sions on this organ. But when they have attempted to explain why the interruption of all communication between the brain and the heart does not stop the motions of the latter, they have been obliged to abandon the gene- rally received opinion, which regards the brain as the only centre and source of nervous power, and have admitted, without any direct proofs, that that power is generated throughout the whole extent of the nervous system^ even in the smallest nerves, and that it can exist for a certain time in the nerves of any part inde- pendently of the brain. Among the authors of this opinion, the learned Professor Prochaska is one of those who has given the best account of it.* But when he applies it to the motions of the heart, and attempts to explain why they are independent of the will and yet influenced * Commentatio de functionibus systematis nervosi, pub- lished in the third fasciculus of the Adnotationes Academ. of this writer, and re-printed at Vienna in his Opera Minora, in 1800. 13 by the passions, his opinion appears undecided. He has recourse to the ganglions, and hesitates what function to ascribe to them. Sometimes he considers them as knots, as ligatures, so tight as to intercept all communication between the heart and Sensorium Commune, in the calm and peaceful state of the system, but not suf- ficient to prevent the Sensorium re-acting more or less powerfully on the heart in the agitation of the passions.* Sometimes he seems to be- lieve that the interception is complete and con- stant, and that it is by the nerves of the eighth pair that the passions affect the heart ;f and he seems to adopt the opinion of Winslow,J re- newed by Winterly Johnstone, || Unzer,^[ Le- cat,** Peffinger,tf &c. that the ganglions are so many small brains. He admits at the same time that the nerves of feeling are distinct from those of motion, so that the heart cannot contract except when the impression of the stimulus on * Opera minora, Tom. 2, p. 165. t Ibid, p. 167. \ Exposit. Anatom. Traite des Nerfs, § 364. § Nov. Inflam. Theoria, Viennee, 1767, cap. 5, p. 154. II Essay on the use of the Ganglions, 1771. f Unzer quoted by Prochaska oper. minor. Tom. 2. p, 169. ** Traite de l'existence de la nature et des proprietes du fluide nerveux, Berlin, 1765, p. 225. tt De structura nervorum, Argentorati, 1782, Sect. 1, § 34. inserted in the Collection of Ludwig, vol. 1. 14 its cavities is transmitted to the ganglions by the nerves of feeling, and reflected on its fibres by the nerves of motion.* But besides that this opinion, even by the author's confession, is only a conjecture, it supposes on the one hand, that the circulation would continue after the destruc- tion of the spinal marrow; and on the other, that the heart would cease to beat at the moment when its communication with the ganglions and the Plexus is interrupted. Now both these sup- positions are contradicted by facts. These fruitless attempts to modify the theory of irritability by the intervention of the nerv- ous power, have only increased the zeal of some authors to maintain that theory in its original purity, and as the use of the nerves of the heart was among the most embarrassing objections to it, M. Scemmerring, one of the most pro- found Anatomists of Germany, and Behrends, one of his most distinguished scholars, main- tained, in 1792, that the heart has no nerves, and that all those which appear to enter it are expended on the coats of the coronary arteries, without the fibres of the heart receiving a single thread;! an opinion which far from removing '* Opera Minor. Tom. II. p. 169. t Behrends Dissertatio qua demonstratur cor nervis ca- rere, Moguntiee, 1792, inserted in the third vol. of the Col- lection of Ludwig. 15 all the difficulties, only renders the influence of the passions on the motions of the heart more inexplicable. These two authors maintain that the cardiac nerves support and increase the irri- tability of the coronary arteries; but the exist- ence of irritability in the arteries is still doubt- ful, and were it demonstrated, it would be very strange if irritability depended on the nervous influence in the arteries; and in the heart, the most irritable of all the organs, it were wholly independent of this influence. Science, however, has cause to rejoice at the groundless doubts proposed by M. Behrends respecting the cardiac nerves, since they have induced the learned Scarpa to take part in the dispute, and have procured for us his excellent work on the nerves of the heart.* M. Scarpa proves in that work that the nerves of the heart are as numerous, and are distributed in the same way, as in other muscles. He admits with M. Prochaska, that sensibility and irrita- bility are essentially united,' and that the ner- vous influence is generated throughout the whole extent of the nerves ; but he does not admit that the ganglions are so many little brains.! He seems to believe that the nerv- * Tab. neurolog. ad illust. hist. anat. cardiacorum nervo-, i-unu&c. Ticini, 1794. t Ibid, § 30. 16 ous influence, such as it exists in all the nerves, is of itself sufficient for the exercise of the different functions, and that it only wants the stimulus which excites it to action. That the stimulus of the muscles of voluntary motion comes from the brain, and that in ordinary states the blood is the stimulus of the heart: but that in vivid emotions the brain also becomes a stimulus to this organ.* According to this opinion the heart ought to beat in the same manner, and with the same force, after decapitation, after the destruction of the spinal marrow, and after it is removed from the body. M. Scarpa himself compares the beat- ing of the heart in apoplexy to that which we observe when it no longer communicates either with the brain or spinal marrow.! But we shall see in the sequel that it is very different. We must not omit a very important remark of this author, and which it is surprising was not sooner made. It respects the insensibility of the heart when we irritate the spinal marrow and the cardiac nerves. M. Scarpa observes, that that insensibility of which so much has been said, and which has been regarded as a demonstrative proof that the motions of the heart do not depend on the nerves, proves only * Ibid, § 22, 24, 25, 26, 27, 29. t Ibid, § 25. 17 that the nerves of the heart are not of the same kind with those of the muscles of volun- tary motion, and that the nervous power does not in them obey the same laws.* This re- flection is without doubt very judicious, and it is by an error of experimental logic that we are surprised not to obtain the same effects from the irritation of two orders of nerves wholly different. The work of M. Scarpa did not induce Dr. Soemmerring! to change his opinion, nor pre- vent Bichat from denying that the nervous power has any share in the /motions of the heart.f This last writer maintains the existence of an animal and organic life, distinct from each other, and of a nervous system for each of these lives. The system of the ganglions, which he regards in the same point of view with the authors above quoted, as small brains, belong to the organic life, and the cerebral system to the animal life.§ To be consistent with him- self, Bichat should have admitted, like M. Pro- chaska, that the heart, the centre of organic life, * Ibid, § 20. t Th. Soemmerring de corporis humani fabrica. Trajecti ad Meenum, 1796. Tom. III. p. 30, 43, 46, 50, et ibid, 1800, Tom. V. p. 43. 1 Bichat. Recherch. Phys. sur la vie et la mort. Paris, 1800, Part II. Art. 11, § 1. § Ibid, Part I. Art. 6, § 4. Ibid, Art. 1, § 2. 5 18 derives from the ganglions the principle of its motions ; but he has not done so. It is chiefly the galvanic experiments which has brought him into this inconsistency, because he had attempt- ed in vain to produce contractions in the heart by galvanising the cardiac nerves ; experiments on which M. Soemmerring and Behrends had also endeavoured to support their opinion.— These experiments may always succeed, as one of us found in 1797;* and three years before was found by Mr. Fowler.! Such is a short but faithful account of the principal systems, by means of which authors have since the discovery of the circulation of the blood to this day, attempted to explain the motions of the heart. On taking a general view of them we remark, that in all those invented before Haller,! the nervous power is considered, in one way or other, as one of the conditions essential to the production of the motions of the heart; and it is always and only in the brain that they place the seat of it. The cardiac nerves, therefore, had a determined * M. de Humboldt. Experiences sur 1' irritation de la fibre nerveuse et musculaire, publiees en 1797, et traduites en Francois deux ans apres, Tom. I. Chap. 9. t Experiments on Animal Electricity, by Richard Fowler, 1794. \ Also in those of Ens, of Stcehelin, and others of whom we have spoken. , 19 use in all these systems, and one could easily understand why the heart is subject to the em- pire of the passions; but it was impossible to explain why the circulation continues in acepha- lous animals, and why in experiments on ani- mals, the interruption of all communication be- tween the brain and the heart does not stop the motions of the latter. Since Haller, irritability has been the basis of all these systems. In re- garding that property as essential to the fibre and independent of the nervous influence, the circulation in acephalous animals, and the dif- ferent phenomena observed in the experiments alluded to, present nothing that is not easily un- derstood ; but the use of the nerves of the heart and the influence of the passions on that organ become inexplicable. The necessity of remov- ing these difficulties has produced two parties among the supporters of irritability. The one, zealous favourers of the doctrine of pure irrita- bility, called to their aid the most improbable hypotheses, and all their efforts have only serv- ed to prove how difficult it is to support the cause they espouse. The other confounded the nervous power with irritability, which they con- sider as one of the functions of that power ; but they have been obliged to admit, either with re- spect to the seat, or the manner of existence, of the nervous power, conditions, which, by their own confession, are far from being demonstrated^ 20 respecting which they are not agreed, and which, in the application they make of them to the mo- tions of the heart, either do not wholly remove the old difficulties or create new ones. One may easily see why so little progress has been made in this great and long disputed ques- tion. If we examine all that has been said on the subject since the days of Haller, we shall find, that both sides have constantly brought for- ward nearly the same facts, the same experi- ments, and the same reasonings. The only new experiments are the applications of galvan- ism to stimulate the cardiac nerves ; and they are only new in appearance, for from the time of Haller electricity has been employed with the same view.* It is evident that science had nothing to expect from our pursuing a path trodden for nearly sixty years by so many cele- brated men. It was necessary to open new roads; it was necessary to find or invent new modes of interrogating nature. It was, above all, necessary to introduce into physiological ex- periments, that precision and severe logic to which other branches of physical science have, in our days, owed so great progress. It is this which the author of the memoir before us has done. ■• * See, amongst others, Mem. sur les parties sensib. et fr- ritab. Tom. IIL p. 214. 21 It was not the original object of M. le Gallois to explore the cause of the motions of the heart. He had adopted the theory of Haller on this subject, when experiments undertaken with other views led him to the singular conclusion, that it was impossible for him to understand his own experiments, without determining whether the nervous power . influences the motions of the heart; and if so, in what way it has this effect. To make his work better understood, we shall relate on what occasion, and by what chain of facts and reasonings he was led to engage in this inquiry. A peculiar case of labour some years ago excited in him a wish to know how long a full- grown foetus can live without breathing, after all communication between it and the mother has ceased. That question, curious in itself, and of the first importance in the practice of midwifery and medical jurisprudence, had hard- ly been touched upon by authors. M. le Gal- lois undertook to resolve it by direct expe- riments on animals; and that the solution might be generally applicable, and extend to as many cases as possible, he placed the foetus of animals in various situations similar to those in which the human foetus is occasionally placed, when it ceases to communicate with the mother. Among these there is one which occurs too often, namely, the foetus suffering decollation from arti- 22 ficial delivery by the feet. The author wished to know what happens to the foetus in this case, whether it perishes at the instant of decollation, and how death takes place. He found that the trunk retains its life, and that if hemorrhage be prevented, by throwing a ligature round the ves- sels of the neck, it dies in the same time and with the same symptoms as if, without taking off the head, respiration had been interrupted; and what ^completely demonstrated to him that a decapitated animal is in fact suffocated, is, that we may at pleasure prolong its existence by inflating the lungs to supply the place of natural respiration. M. le Gallois concluded from these facts, that decollation proves fatal by destroying the motions of inspiration, and that consequently the power on which these motions depend is in the brain; but that that on which the life of the trunk de- pends is in the trunk itself. Endeavouring to as- certain the precise seat of each of these powers, he found that that on which the motions of inspi- ration depend resides in that part of the medulla oblongata from which the eighth pair of nerves take their rise; and that on which the life of the trunk depends, in the spinal marrow. It is not by all the spinal marrow that every part of the body is animated, but only by that portion from which it receives its nerves; so that in destroying any particular part of the spinal marrow, we only destroy life in those parts of the body which cor- 23 respond to that part. Besides, if we interrupt the circulation in any particular part of the spinal marrow, life is weakened, and soon extinguished in all the parts which receive nerves from it. There are, therefore, two ways of destroying life in any part of an animal; the one destroying that part of the spinal marrow from which it receives its nerves, the other interrupting the circulation in this part of the spinal marrow. It hence results, that two conditions are neces- sary to preserve the life of any part of the body, viz. the integrity of the corresponding part of the spinal marrow, and the circulation of the blood, and consequently that we may preserve life in any part of an animal as long as we can preserve in it these two conditions. We may, for exam- ple, preserve the life of the anterior parts after that of the posterior parts is destroyed, by de- stroying the corresponding portion of the spinal marrow, or vice versa. M. le Gallois, whose constant practice was to seek in direct experiments a confirmation of the consequences which he deduced from preceding ones, wished to know if in fact it is possible to make any particular part live after the others are dead. In a rabbit twenty days old he destroyed all the lumbar portion of the spinal marrow. This operation occasioning no immediate injury to the rest of the spinal marrow, and, according to the theory of Haller, the circulation not being affect- 24 ed by it, he had every reason to expect, reason- ing from the preceding experiments, that the ani- mal would have lived for a considerable length of time, and that it would only have died in con- sequence of the symptoms produced by so severe an injury; but the respiration ceased in a minute or two, and in less than four minutes it shewed no sign of life. This experiment was repeated seve- ral times with the same result, nor was it possible to prevent it. Thus it was proved, that a rabbit of twenty days old cannot survive the loss of the lumbar portion of the spinal marrow ; which ap- peared the more surprising, because rabbits of this age continue to live very well after decapita- tion, that is, after the total loss of the brain. This fact, which the author could not reconcile with his preceding experiments, led him to discover, that the power on which the action of the heart de- pends fie principe des forces du cozurj resides in the spinal marrow. M. le Gallois then ascertained that the de- struction of either the dorsal or cervical portion of the spinal marrow was fatal to rabbits of twenty days old, even in a shorter time than that of the lumbar portion, in about two mi- nutes. He found that the same experiments re- peated on rabbits of different ages did not give the same results. In general the destruction of the lumbar portion was not suddenly fatal to rabbits under ten days old, and some at the 25 age of fifteen days survived it. Beyond twen- ty days old the effect is the same as at this age. Very young rabbits continued to live after the destruction either of the dorsal or cervical portion, but for a shorter time ; and in a smaller number of cases, after the destruction of the latter than after that of the dorsal portion. None after the age of fifteen days survived the destruc- tion of either. In all those partial destructions of the spinal marrow, even where the death is sudden, it is in- stantaneous only in the parts which receive their nerves from the destroyed part, and only extends to the rest of the body at the end of a certain time; but this time is fixed, and no means can prolong it. It is the same in animals of the same kind and of the same age; and the longer, the nearer the animal is to the time of its birth. For example, when the cervical part of the spinal marrow is destroyed in rabbits, life is instantly lost in the whole of the neck ; but it continues in the head, as appears from the gaspings it excites; it continues also in the parts below the shoulder, as the continuance of their feeling and voluntary motion shews. In the first day after birth, the gaspings continue about twenty minutes, the sen- sibility and motion of the rest of the body fifteen minutes. At the age of fifteen days, the duration of the gaspings does not exceed three minutes ; that of sensibility and motion two and a half. In 6 26 fine, at the age of thirty days the gaspings cease in a minute and a half, and the sensibility in a minute. After the destruction of the dorsal por- tion of the spinal marrow, it is the chest and not the neck which is instantly struck with death. In other respects the phenomena and their duration are the same. If the three portions of the spinal marrow are destroyed at once, the gaspings, the only signs of life which then remain, have still, at the different ages, the durations just pointed out. The author, who had so often decapitated rab- bits of different ages, had always remarked that the head, separated from the body, continued to gasp during a time determined by the age. This time was evidently the same as after the de- struction of the spinal marrow. Now it is evi- dent that after decapitation there can be no longer any circulation in the head, and that the gasp- ings which take place in that case can only con- tinue for the time during which life may exist in the brain, after the total ceasing of the circula- tion. This was the first indication which M. le Gallois had, that when the partial destruction of the spinal marrow occasions death throughout all the rest of the body, it is because it suddenly arrests the circulation. To assure himself of this, he cut out the heart at the base of the great ves- sels, in rabbits of every fifth day old from birth to the age of a month: and having noted with 27 care the duration of the different signs of life from the moment at which the circulation was thus stopped, he found, that their duration was precisely the same as after the destruction of the spinal marrow. He might have considered this coincidence as sufficient to decide the question; but he wished to ascertain in a more direct man- ner if the circulation actually ceases at the mo- ment the spinal marrow is destroyed. The ab- sence of hemorrhagy and the emptiness of the arteries were the most evident signs that he could have of the circulation having ceased; and he found, in fact, that soon after the above ope- ration, the carotids were found empty, and the amputation of the limbs occasioned no hemorr- hagy, though performed near to the trunk, and before life was extinct in the parts of which the spinal marrow had not been destroyed. In a word, all the signs which shew the state of the circulation demonstrated to him, that when the destruction of any part of the spinal marrow sud- denly occasions death in the rest of the body, it is by stopping this function, and this effect takes place not because the motion of the heart imme- diately ceases, but because it is no longer capa- ble of throwing the blood even into the carotids. Hence it follows, that it is in the spinal mar- row that the power on which the motion of the heart depends resides, and in the whole of it, since the destruction of any one of its three por- 28 tions is capable of stopping the circulation. It also follows, that each portion of the spinal marrow influences life in two different ways; by the one it is essential to the existence of life in the parts which receive nerves from it; by the other, it preserves it throughout the body in general, by contributing to furnish to the organs which re- ceive nerves from the great sympathetic, and par- ticularly to the heart, the life and power, fie principe de force et de vie, J necessary to the performance of their functions. Thus we see, that to make the anterior or pos- terior parts of an animal live after killing the rest of the body, by destroying the corres- ponding parts of the spinal marrow, we must prevent the destruction of these parts from stop- ping the circulation. Now this is easily done by diminishing the sum of the forces, which the heart must impart for the support of the circula- tion, in proportion as we diminish the power which it receives from the spinal marrow. It is sufficient for this purpose to diminish by liga- tures, thrown round the arteries, the extent of the parts to which the heart sends the blood.— We have seen, for example, that the destruction of the lumbar part of the spinal marrow is quick- ly fatal to rabbits at or beyond the age of twenty days; but this is not the case if we previously throw a ligature round the ventral aorta between the cceliac and anterior mesenteric arteries. 29 The application of this principle to other parts of the body leads to the singular conclusion, that in order to maintain life in rabbits of a certain age, after the destruction of the cervical part of the spinal marrow, we must previously cut off the head. They certainly die if this part of the spi- nal marrow is destroyed without previous decapi- tation. This fact ceases to surprise, when we reflect that by decapitation, we lessen by the head the extent of the circulation, and that by that means the heart having need of less force to sup- port the circulation, we may enfeeble it by the de- struction of the cervical part of the spinal mar- row, without destroying the circulation. One may easily conceive that any other opera- tion capable of suspending or considerably en- feebling the circulation in any part of an animal may produce a similar effect; and enable us in like manner, to destroy such a portion of the spi- nal marrow, as would have been fatal without this previous operation. This is what happens in the partial destruction of the spinal marrow itself. It has two effects on the circulation; by the one it enfeebles it, generally by depriving the heart of that share of its power which it receives from the part of the spinal marrow that has been destroyed ; by the other, without wholly destroy- ing the circulation in the parts which are thus de- prived of life, it in a great degree lessens it in a 30 way in some measure similar to the effect of liga- tures thrown round the arteries of these parts. But this effect is not remarked till a few minutes after the destruction of the spinal marrow. Thus it is the destruction of the first part of the spinal marrow which enables us to destroy a second. This a third and so on. For example, when, by decapitating a rabbit, we are enabled to de- stroy the cervical part of the spinal marrow, the destruction of that part in a certain number of mi- nutes enables us to destroy the fourth part of the dorsal portion of the spinal marrow, and thus by continuing to destroy parts of similar extent, by intervals, we may at length destroy the whole of this portion of the spinal marrow without stop- ping the circulation, which is then supported by the lumbar portion only. We may collect from what has just been said, that in rabbits, each portion of the spinal marrow bestows on the heart power sufficient to support the circulation in all those parts which correspond to that portion, and consequently, that in cutting a rabbit transversely, it would be possible to make each portion live for an indefinite time, if the lungs and the heart, necessary for the formation and circulation of arterial blood, could make part of it. But they can only make part of the chest, and one may very well maintain the life of the chest alone and insulated, after having cut off 31 both the anterior and posterior parts, and prevent- ed hemorrhagy by proper ligatures, and that even in rabbits thirty days old or more. Such are the principal results of M. le Gallois' researches, results which arise one from the other, and mutually supporting each other, are founded on direct experiments, made with a precision hi- therto unknown in Physiology. We are now going to relate such of those experiments as the author repeated in our presence. We devoted to these repetitions three meetings, each of several hours duration : and, in order to avoid all preci- pitation, and to give us time to weigh the facts at leisure, we allowed a week to intervene between the meetings. Experiments repeated before the Committee of the Institute. We shall divide them into two parts; the first will comprehend those which tend to prove that the origin of all the motions of inspiration reside in that part of the medulla oblongata which gives rise to the eighth pair of nerves. In the second we shall relate those whose object is to prove that the heart derives its power from the spinal marrow. 32 ist. Experiments relating to the power on which the motions of inspiration depend. The author, in a rabbit of five days old, detach- ed the larynx from the os hyoides, and exposed the glottis that we might observe its movements; after which he opened the head, and first extract- ed the cerebrum and then the cerebellum. After these operations the inspirations continued ; they were each characterised by four simultaneous movements, namely, a gasping, the opening of the glottis, the elevation of the ribs, and the contrac- tion of the diaphragm; these four movements hav- ing been observed, and found to continue for a certain time, according to the age of the animal, the author extracted the medulla oblongata, and in a moment these movements ceased altogether. The portion of the medulla oblongata which was extracted extended to the occipital hole, and in- cluded the origin of the eighth pair of nerves. The same experiment was repeated on another rabbit of the same age, with this difference, that after the extraction of the cerebrum and cerebel- lum, instead of removing so large a portion of the medulla oblongata all at once, it was extracted successively, by portions of about the thickness of three millimetres. The four motions of inspira- tion continued after the extraction of the three first slices, but ceased immediately after that of 33 the fourth; we found that the third slice termi- nated at the posterior part, and very near to the pons varolii, and that the fourth embraced the origin of the nerves of the eighth pair. This experiment repeated on other rabbits con- stantly gave the same result. The same experiment was made on a cat five weeks old, except that before the medulla oblon- gata was removed by slices the two recurrent nerves were divided. The glottis immediately closed and remained immoveable, but the three other motions, namely, the gaspings, the eleva- tion of the ribs, and the contractions of the dia- phragm continued, and only ceased at the mo- ment when that portion of the medulla oblongata, in which the eighth pair of nerves originate, was removed. It is evident that if in place of destroying that part from which all the motions of inspiration are derived, one only cuts off the communication between it and the organs which perform these motions, he will produce the same effect; that is to say, will stop those motions whose organs have no longer any communication with the part in question. This is what we have just seen happen in the cat, in which the division of the recurrent nerves stopped the motions of the glot- tis without stopping the other three motions. In order to suspend these it is sufficient to observe how their organs communicate with the medulla 7 34 oblongata. Now it is clear that it is by the in tercostal nerves, and consequently by the spinal marrow, that the medulla oblongata acts upon the muscles which raise the ribs, and that it is by the phrenic nerves, and consequently by the spinal marrow also, that it acts on the dia- phragm. In dividing the spinal marrow about the last cervical vertebra, and below the origin of the phrenic nerves, one ought therefore to stop the motions of the ribs, but not those of the dia- phragm : and in dividing the spinal marrow be- tween the occiput and the origin of the phrenic nerves, we ought to destroy at once the motions of the ribs and those of the diaphragm, and this is in fact what happens. The author, after the motions of the thorax had been well observed in a rabbit about ten days old, divided the spinal marrow about the seventh cervical vertebra. Such of these motions as depend on the eleva- tion of the ribs, immediately ceased, but the con- traction of the diaphragm continued. He then divided the spinal marrow about the first cervical vertebra, and immediately the diaphragm ceased to contract. Lastly, he divided the eighth pair of nerves about the middle of the neck, and the motions of the glottis ceased. Thus of the four motions of inspiration there remained only the gaspings, which shewed that the medulla ob- longata still preserved the power to produce all the motion, and that it only failed to produce the 35 other three because it no longer had any commu- nication with their organs. We ought to observe here, that several authors, amongst others Arne- mann, before M. le Gallois, had observed that the division of the spinal marrow only stopped the motions of the diaphragm when it was made between the occiput and the origin of the phrenic nerves; but these authors regarded the brain as the only source of life, and of all the motions of the body. They thought, accordingly, that the division of the spinal marrow instantly paralyzed all parts of the body whose nerves arose from the spinal marrow below the part at which it was divided, and, therefore, that when the di- vision was made near the occiput the diaphragm ceased to contract, because it partook of the pa- ralysis of all the parts below the division. But M. le Gallois has demonstrated, that the division of the spinal marrow, made about the first or last cervical vertebra, only stops the motions of in- spiration, and allows to remain throughout the body both feeling and voluntary motion. This distinction is essential. No person made it be- fore him. It is not only in warm blooded animals that these experiments produce the results which we have described. To prove that these results be- long to the general laws of the animal economy, and that the nervous power obeys the same laws in all vertebral animals, the author took a frog, 36 and after having remarked that in these animals, which have neither ribs nor diaphragm, there are but two kinds of motions of inspiration, namely, those of the glottis, which opens in the form of a lozenge, and those of the throat, which is alter- nately raised and lowered, he cut off the anterior half of the brain, the two motions continued ; he then destroyed about the half of that which re- mained ; the motions still continued. In fine, he carried the destruction of the brain as far as the occiputal hole, and the two motions instantly ceased. In another frog he divided the spinal marrow about the third vertebra, the motions of inspiration continued. In a third frog it was di- vided between the occiput and the first vertebra, the motion of the throat, which represents that of the diaphragm, immediately ceased. After these two last experiments the frogs were and remain- ed alive, both in the head and the rest of the bo- dy ; but they could not govern their motions, and in this respect were in the same state as the first frog, whose brain had been destroyed. %d. Experiments relative to the principle on which the power of the heart depends. The author has already proved that life always continues for a certain time, even in warm blood- ed animals, after the total ceasing of the circula- tion, and that the length of this time is influenced 37 by the age of the animal. He opened the chest and cut out the heart of a rabbit of five or six days old ; he did the same in another of ten days old. In the first the gaspings ceased in seven minutes, and the sensibility in four after the ex- cision of the heart. In the second the gaspings lasted only four minutes and the sensibility only three. The cervical and a small portion of the dorsal part of the spinal marrow were then de- stroyed in another rabbit of the same litter with the last, and immediately afterwards the lungs were inflated; notwithstanding this assistance the gaspings ceased at the end of three, minutes and a half, and the sensibility in a little more than two and a half; periods which coincide, we see, to nearly half a minute with those observed after the excision of the heart. In order to prove that in this experiment it is really by stopping the circulation that the de- struction of a part of the spinal marrow destroys the life of the rest of the body, the author divid- ed the spinal marrow of a rabbit of the same age with the two last, near the occiput. After this division the carotid arteries were black, but round and full, and on the amputation of a limb, black blood flowed; having inflated the lungs, the caro- tids quickly regained a fine red colour, and blood also flowed from the limb of the same colour. These appearances left no doubt that the circula- tion continued after the division of the spinal 38 marrow near the occiput. The author then de- stroyed in this rabbit the same portion of the spi- nal marrow as in the preceding. The carotids instantly became flaccid, and soon appeared emp- ty and flat. The two thighs amputated in less than two minutes after the destruction of the spi- nal marrow did not supply a drop of blood. The destruction of the cervical part of the spi- nal marrow in several other rabbits, from twenty to thirty days old, gave precisely the same re- sults, that is to say, the carotids soon appeared empty, and no blood flowed on the amputation of the limbs ; and notwithstanding the most careful inflation of the lungs, the signs of life remained no longer than after the excision of the heart, ac- cording to the tables which M. le Gallois has given of the different ages in his paper. The results were the same with respect to the emptiness of the carotid arteries, the absence of hemorrhagy, and the duration of life after the de- struction of the dorsal part of the spinal marrow. The destruction of the lumbar part of the spi- nal marrow in rabbits of four and five weeks old gave similar results, with this only difference, that the circulation did not stop immediately, as after the destruction of the cervical and dorsal parts of the spinal marrow; but at the end of about two minutes, and in one case at the end of four minutes, which proves that the action of the lumbar part of the spinal marrow upon the heart, 39 though evident and very great, is not so imme- diate as that of each of the other portions. After having proved by these experiments that the circulation depends on all parts of the spinal marrow, the author shewed us that there is none of these portions which may not be destroyed with impunity, if we confine to a certain space the parts to which the heart sends the blood.— After opening the belly of a rabbit six weeks old, he threw a ligature round the aorta, between the cseliac and anterior mesenteric arteries, after which he destroyed the whole of the lumbar part of the spinal marrow. This rabbit continued quite alive, supporting itself upon its fore legs, and holding up its head more than half an hour afterwards, when the Committee finished their sitting, while another rabbit of nearly the same age, used for the sake of comparison, in which the lumbar portion of the spinal marrow had been destroyed without securing the aorta, died in less than two minutes. M. le Gallois then made the experiment of destroying the cervical portion of the spinal mar- row, the action of which upon the heart is more immediate, and still more considerable than the lumbar, in rabbits of five or six weeks old, with- out stopping the circulation. After having de- capitated the animal with the ordinary precau- tion, he performed artificial inspiration during five minutes, at the end of which he destroyed 40 the whole of the cervical part of the spinal mar- row ; he renewed the artificial inspiration imme- diately after, and the animal remained alive as long a time as it was judged proper to continue the artificial respiration. The same experiment was repeated with the same result on two other rabbits of the same age; in one of these, five mi- nutes after having destroyed the cervical part of the spinal marrow, the author destroyed about one-third of the dorsal part of the spinal marrow, then five minutes after a second third, and the remaining part again in five minutes. The cir- culation and the life of the animal continued af- ter the destruction of the two first third parts, and only ceased after that of the last. During the whole of the experiment artificial respiration had only been interrupted for the time necessary for the destruction of the spinal marrow. These experiments led M. le Gallois to that much more difficult one, the object of which is to prove, that in limiting by ligatures the circula- tion to those parts which correspond to any par- ticular portion of the spinal marrow, that portion gives to the heart power to support the circula- tion in those parts. He separated the upper and lower from the central parts in a rabbit of thirty days old, dividing it below about the first lum- bar vertebra, and above about the second cervi- cal vertebra, then by artificial respiration he sup- ported life in the chest thus isolated. We do not 41 describe the particulars of the operation, because the author has detailed them in his memoir. We shall confine ourselves to say, that the experi- ment succeeded perfectly, although an artery, which could not be secured, occasioned a consi- derable hemorrhagy, and risked the success of the experiment. In fine, M. le Gallois produced partial death in the hinder parts of the body in a rabbit of about twelve days old, by tying the aorta be- tween the cseliac and anterior mesenteric arteries. At the end of twelve minutes the death of the parts appearing complete, he untied the artery, and life by degrees appeared in the whole of these parts, so that the animal was able to walk with ease. This partial resurrection proved that we might succeed in the same way with the whole body, if it were possible to re-establish the circu- lation after the extinction of life in the whole of the spinal marrow; but the experiments of the author demonstrate much better than had been done before him, why the renewal of life in the whole body is impossible. The author has also made, in our presence, some experiments on Guinea pigs, from which it appears, that in these animals the power of the heart equally depends on the spinal marrow, only it was necessary to destroy greater portions of it, in order to stop the circulation, than in rab- bits of the same age. 8 42 We shall finish the account of the experiments which M. le Gallois repeated in our presence, by those on cold blooded animals, the results of which are altogether in contradiction to those which the most zealous partizans of Haller, and among the rest, Fontana,* have obtained, and which have been so much valued. The author opened, on the one hand, the cranium, and on the other, the chest of a frog, and brought the heart into view; he then fixed the animal firmly,! and while one of us observed the motions of the heart, measuring seconds with a watch, he de- stroyed the brain and the whole of the spinal marrow by a stilet, introduced by the opening in the cranium: in an instant the motions of the heart stopped, and were not renewed for several seconds, and the rate of their repetition never again became the same : they were more frequent than before the destruction of the spinal marrow. The same experiment repeated on five frogs con- stantly gave the same results; the motions of the heart were not suspended the same number of se- conds in all, but the suspension was always very remarkable, as well as the change in the rate of beating. We may add, that the amputation of r Fontana. Mem. sur les parties sensib. et irritab. Tom. III.p. 231. Traite surlevenin de la vipere, &c. Florence, 1781, Tom. II. p. 169, 171. t Ibid. p. 233 of the first of the above works, and 171 of the second. 43 the thighs of frogs, after the destruction of the spinal marrow, occasioned no hemorrhagy; and salamanders, decapitated after a similar opera- tion, in like manner lost no blood, while both in the one case and the other there had been he- morrhagy when the spinal marrow was allowed, to remain entire. These experiments appear to us completely to confirm all the inferences which the author has deduced from them, and with which he finishes his memoir. To confine our- selves here to the principal points we shall say, that we regard as demonstrated, 1st. That the cause of all the motions of inspi- ration has its seat near that part of the medulla oblongata which gives rise to the nerves of the eighth pair. 2d. That the cause which animates each part of the body resides in the part of the spinal mar- row from which the nerves of that part are de- rived. 3d. That in like manner it is from the spinal marrow that the heart derives its life and its powers ; but, from the whole spinal marrow, and not merely from any particular part of it. 4th. That the great sympathetic nerve takes its rise from the spinal marrow, and that the particular character of that nerve is to bring eve- ry part to which it is distributed under the im- mediate influence of the whole nervous power. These results readily explain all the difficuj- 44 ties which have arisen since the days of Haller respecting the causes of the motions of the heart. The reader will recollect that the principal of these are, 1st. Why does the heart receive nerves ? 2d. Why is it influenced by the pas- sions? 3d. Why is it not subjected to the will? 4th. Why does the circulation continue in ace- phalus and decapitated animals ? He will recol- lect also, that till now no explanation has been able to reconcile these points, or at least has not been able to do so without the aid of hypotheses which we have seen give rise to other difficulties. But now we easily conceive why the heart re- ceives nerves, and why it is so eminently subject to the influence of the passions, because it is ani- mated by the whole of the spinal marrow. It does not obey the will, because none of the or- gans which are under the influence of the whole nervous power are subject to it. In fine, the cir- culation continues in acephalus and decapitated animals, because the motions of the heart do not depend on the brain, or only depend upon it in a secondary way. We ought to remark, that this last point, on which M. le Gallois has thrown so much light, presents only confusion and errors in authors of the old school of Haller, as well as in those of the new school. None of them have dis- tinguished the motions of the heart which take place after decapitation, from those which we ob- serve after the excision of this organ, or after the 45 destruction of the spinal marrow ; and they have thought that both were equally capable of main- taining the circulation. But these motions differ essentially. The latter have no power to sup- port the circulation; they are quite similar to the feeble movements which we may excite in the other muscles for some time after death. M. le Gallois calls them motions of irritability, without attaching for the present any other meaning to the term, but that of expressing certain phenomena after death. We have still one task to perform, to point out 'what particularly belongs to M. le Gallois in the work which is the object of this report, and what others are entitled to claim. We can affirm without fear of contradiction, that every thing in this work belongs to him.— To be convinced of this, it is only necessary to read his memoir with attention. Chance suggest- ed to him the idea of his first experiment, and that experiment led him to all the others, each of them being suggested to him, and as one may say, forced upon him by that which preceded it. In following him step by step, one observes that his own method has been his only guide, and that it is that alone which has inspired him. Thus, it is a thing without example in Physio- logy, to see a work of such length, in which all the parts are so connected, so dependent on each other, that to have the complete explanation of 46 any one fact, it is necessary to recur to all those by which the author arrived at it, and in which it is impossible to deny one inference without de- nying all those which precede, and disturbing all those which follow it. One might have expected that in researches so numerous, and which, by the importance of the questions they embrace, have commanded the at- tention of a great number of philosophers, the author would often have been led, even in con- fining himself to his own method, to repeat ex- periments which had been made by others; yet among all the experiments found in his memoir we have remarked only two which had been made before him ; one by Fontana, the other by Stenon. The first* consists in inflating the lungs and thus preserving the life of an animal after decapitation. Fontana only made that experi- ment to supply oxygen to the venous blood; and one may easily perceive that he was a stranger to the object before us. As the experiment was un- connected with any other subject, and did not serve as a proof of any point of doctrine, little attention was paid to it; and it was confounded with many other facts, shewing that even warm blooded animals may live after decapitation with- out its being suspected that it was the decapita- * Fontana. Traite sur le venin de la vipere, &c. Tom. I.. p. 317. 47 tion which enabled them to live in that state.— Hence it is that this experiment remained almost unknown except in some of the Schools of Eng- land and Germany; and M. le Gallois was wholly ignorant of it when he communicated to the Society of Medicine at Paris his first inqui- ries into the functions of the spinal marrow. Be- sides, this experiment in the hands of M. le Gallois was only one of the means by which he demon- strated two of his principal discoveries, namely. that the cause of the motions of inspiration has its seat in the medulla oblongata, and that the cause of life in the trunk resides in the spinal marrow. The experiment of Stenon is that in which the ventral aorta is tied and then untied, to shew that the interruption of the circulation in any part oc- casions paralysis of that part, and that the return of the blood restores life to it. This experiment is well known? and has often been repeated. Some of the authors who have made it, had in view to prove that the contractions of the muscles depend on the action of the blood on their fibres; others that the sensibility of every part depends on the circulation; and in both views it served equally to prove or disprove the point, according to the manner in which it was made. Thus, when they secured the ventral aorta, the feeling and motion of the lower parts of the body quickly ceased.* * Lorry, Journal de Med. An. 1757, p. 15. Haller, Mem. sur le Mouvement du Sang, p. 203, Exp. 52. 48 But when the ligature was made lower, aud only on one of the crural arteries, although in this case the circulation was wholly interrupted in the cor- responding member, feeling and motion conti- nued in it for a long time.* In these opposite results each author did not fail to adopt those which favoured his own opinion, and he thought himself authorised to do so, as the real cause of the difference was unknown. In the hands of M. le Gallois the same expe- riment shews itself under a very different aspect, and assumes a determined meaning. It is evi- dent that feeling and motion ceasing in the hinder parts from a ligature being thrown round the aorta, arises from its being only in this case that the circulation is interrupted in that portion of the spinal marrow which gives rise to the nerves of these parts. Such are the only experiments of M. le Gallois, as far as we know, which can be claimed by others ; but besides that the manner in which they make a part of his work renders them his own, it appears to us that the new points of view, under which he presents them, and the precision of the details and clearness of the re- sults which he has substituted for the uncertainty and obscurity in which they were formerly in- volved, have made them experiments wholly new. * Schwenke, Hcematol. p. 8. The 57th and 58th Experi- ments of Haller, p. 205, are of the same kind. 49 We shall finish by a few words on an opinion of M. Prochaska, which may be believed to be similar to that, which M. le Gallois has demon- strated respecting the functions of the spinal mar- row. That author places the sensorium com- mune in the brain and spinal marrow conjoint- ly.* But it is necessary to be aware that he thinks that the nervous power is generated throughout the whole extent of the nervous sys- tem, so that every part derives from its own nerves, taken alone, the cause of its life and of its movements.! He only regards the sensorium as a central point, where the nerves of feeling as well as those of motion meet and communicate, and which establishes the connection between the different parts of the body.| On the contrary, M. le Gallois has demonstrated that the spinal marrow is not merely a means of communication between different parts, but that from it the cause of the life and power of the whole body proceeds. And what proves that M. Prochaska, in announ- cing his opinion, which besides he only mentions as a thing probable, § was far from suspecting the true functions of the spinal marrow, is, that h» * Opera Minor. Tom. II. p. 51. Before him Marherr, Hartley, &c. had been of the same opinion. t Opera Minor. Tom. II. p. 82. t Ib. p. 151. § Ib. p. 155-. 9 50 regards it as only a great bundle of nerves, cras- sus funis nerveus.* In a word, it appears to us that we may say of the authors who have had some views on the subjects of which M. le Gallois treats, what M. Laplace has said with so much justice on a simi- lar occasion. One may there meet with some truths, but they are almost always mixed with so many errors that their discovery belongs only to him, who, separating them from this mixture, succeeds by calculation or observation in effec- tually establishing them.! The opinion of your Committee is, that the work of M. le G allois is one of the most excellent and certainly the most important which has ap- peared in Physiology since the learned experi- ments of Haller; that this work will make an epoch in that science over which it must spread a new light; that its author, so modest, so labo- rious, so meritorious, deserves that the class be- stow on him its especial commendation, and all the encouragement which it can give. They can- not help adding, that the memoir of which they have given an account is worthy to occupy a dis- tinguished place in the Transactions of learned correspondents, if the publicity of the important * Ib. p. 48. t Mem. sur l'Adhesion des Corps a la Surface des Fluides dans la Biblioth. Britan. Tom. XXXIV. p. 33. 51 discoveries contained in it may be deferred to the time, perhaps distant, of the publication of those Transactions. (Signed) DE HUMBOLDT. HALLE. PERCY. The Class approve their Report and adopt its conclusions. It moreover decrees, that the Report shall be printed in the History of the Class, and that the Committee of the Class shall make arrangements with M. le Gallois for defraying the expenses which have been occasioned by his experiments, and enabling him to continue them. Certified to be conformable to the original. G. CUVIER, Perpetual Secretary. CHAP. II. Observations on the foregoing Report. It will be necessary before I enter on the ac count of my experiments to make some observa- tions on the foregoing report. As an account of the state of our knowledge of the subject at the time M. le Gallois began his experiments, it ap- 52 pears to be accurate, well arranged, and suffici- ently comprehensive. As an account of the expe- riments and opinions of this author, nothing, as far as I can judge, can be more clear and cor- rect ; as an estimate of the merits of his work it does not seem to me to deserve the same praise. It overlooks defects, both in his experiments and reasonings, of such moment, as wholly to invali- date all his most important conclusions; and to leave him the discoverer of certain unconnected though most valuable facts, instead of the author of a new system, founded, as the report alledges, on a basis never to be shaken. M. le Gallois has demonstrated, that the sud- den destruction of any considerable portion of the spinal marrow so enfeebles the power of the heart, that it is no longer capable of supporting the circulation. He has also shewn that the same portion of the spinal marrow, whose sud- den destruction destroys the circulation, may be destroyed by small parts without materially af- fecting it. The question then arises, if, as M. le Gallois supposes, the power of the heart is deriv- ed from the spinal marrow, and necessarily ceases when any considerable part of the spinal mar- row can no longer perform its functions, why does the particular mode of destroying it make so great a difference in the result ? This difficulty occasioned so much trouble to M. le Gallois, that it had nearly induced him to abandon the inquiry. 53 u Apres bien des efforts in utiles pour porter la lumiere dans cette tenebreuse question, je pris le parti de 1' abandonner, non sans regret d'y avoir sacrifie un grand nombre d'animaux, et perdu beaucoup de temps." Just before, he ob- serves, " En un mot, j'eus presque autant de re- sultats differens que d'experiences." And in- deed the apparent contradictions in the results of M. le Gallois' experiments are such, as at first view to have persuaded me that some of his ex- periments were inaccurate; on repeating many of them, however, I was convinced of their ac- curacy. He attempts, we have seen, to explain the difficulty in the following manner. He has Shewn that if ligatures be thrown round the large vessels, at no great distance from the heart, so as greatly to lessen the extent of the circulation, this organ can still support it, notwithstanding the destruction of such a portion of the spinal mar- row as would, under ordinary circumstances, have destroyed it. On the same principle ac- coucheurs apply tourniquets to the limbs in cases of profuse uterine hemorrhagy. Now M. le Gallois supposes, that the power of the blood- vessels, as well as that of the heart, depending on the spinal marrow, we greatly impair the vi- gour of the circulation in any part by destroying that portion of the spinal marrow by which its nervous influence is supplied; and, therefore, that when any portion »of the spinal marrow is 54 destroyed by small parts, the vigour of the cir- culation in the corresponding parts of the body being greatly impaired, nearly the same effect is produced as if ligatures had been thrown round their vessels. It might here be objected, that when a considerable portion of the spinal marrow is at once destroyed, the power of the vessels cor- responding to this portion being lost, the effect produced by the ligatures should still be observ- ed. To this I suppose M. le Gallois would have replied, that as it requires some time for the destruction of any part of the spinal marrow to produce its effect on the vessels, when a large portion is destroyed at once, the vessels not ac- commodating themselves to the rapid destruction of the successive parts of the spinal marrow, the circulation is lost. The foregoing explanation resting wholly on the position, that the vessels of any part are de- bilitated when deprived of the influence of the corresponding part Of the spinal marrow, it was incumbent on the Committee to inquire by what experiments M. le Gallois had established it. This question, however, is wholly overlooked by them; and, on reviewing the experiments of M. le Gallois, we find none from which any such infer- ence can be drawn. He attempts to support it only by experiments not properly bearing on the point; although, if the position be correct, the simplest experiments are sufficient to establish it. 55 It is impossible from his experiments to say, whether the diminished circulation in the parts in question arose directly from the destruction of part of the spinal marrow, or from the lessened power of the heart. Another error of even greater consequence than the foregoing in the reasonings of M. le Gallois, which is also overlooked by the Committee, is his inference that the spinal marrow possesses an influence over the heart not possessed by the brain ; because he found that removing the brain produces little or no effect on the action of the heart, while crushing the whole, or a considera- ble part of the spinal marrow, greatly enfeebles it. But to obtain this inference, it is evident that the brain and spinal marrow must be subjected to the same power. They ought both to have been removed or both crushed. The inferences which M. le Gallois makes from the effects of crushing the spinal marrow are in another respect incorrect. There are two ways in which we may account for the power of the heart, or of the blood-vessels, being destroy- ed by crushing the spinal marrow. Either the heart and blood-vessels derive their power from the spinal marrow, and consequently lose it on the destruction of the whole or a considerable part of that organ ; or, deriving their power from some other source, they are influenced by agents acting on the spinal marrow. It was incumbent 56 on M. le Gallois, therefore, to ascertain by ex- periment in which of these ways crushing the spinal marrow produces the effects he observed. But he does not even seem aware, that it may act in any other way than that which he sup- poses. The inference which he draws from the resto- ration to life of the lower parts of an animal when a ligature, which has been thrown round the abdominal aorta, is removed, is inadmissible, namely, that when the circulation in every part is destroyed by crushing the spinal marrow, and we find that we cannot by any means restore it, this is to be ascribed to the absence of the influ- ence of the spinal marrow. The same result may arise, it is evident, from the heart and blood- vessels, supposing them to derive their power from some other source, being so deranged by a powerful agent acting through the spinal marrow, that they are no longer capable of performing their functions. M. le Gallois relates no experi- ment to prove that his explanation ought to be admitted in preference to this; and the Commit- tee speak as if no inference, but that of M. le Gallois, could be drawn from tne experiment. Nor is M. le Gallois' inference respecting the origin of the great sympathetic nerve warranted by his experiments; namely, that it arises wholly from the spinal marrow. It is true that he has found, that through this nerve a powerful agent, 57 applied to any considerable portion of the spinal marrow, is capable of enfeebling the power of the heart; but nothing said by M. le Gallois proves that this is not also true of the brain. A position on which much of the reasonings of M. le Gallois rests, which is admitted by the Committee, but of which we find no proof in the experiments of this author, is, that the contrac- tions of the heart, after it is removed from the body, are of a nature different from those which support the circulation. Observing that after the spinal marrow is crushed, the contractions of the heart are too feeble to support the circulation; without further inquiry he concludes, that these contractions do not merely differ in degree from those which support the circulation, but, existing independently of the spinal marrow, are wholly of a different nature. The contractions of the heart, after it is removed from the body, are re- garded by M. le Gallois as analogous to those which remain after the spinal marrow is crushed, and he regards in the same light the contractions which may be excited for a short time after death in the muscles of voluntary motion. Had M. le Gallois' mind been unbiassed by his peculiar views of the subject, he would have easily ob- served a striking difference between the action of the heart, immediately after the spinal marrow is crushed, and its action immediately after it is re- moved from the body. In the former instance, it 10 58 is feeble and fluttering, gradually becoming ra- ther stronger and more regular ; int the latter in- stance, it is comparatively strong and regular, gradually, and in the cold blooded animal very slowly, becoming more feeble. With respect to the contractions of the muscles of voluntary mo- tion after death, it is generally known that these muscles may for some time be excited to the per- fect performance of their function. They can be made to move the limbs precisely as they did be- fore the death of the animal. But whether they move them as forcibly or not, and whether or not the heart beats as forcibly after it is removed from the body, as while it supported the circulation, as far as we can see, the action of both is of the same nature as when they performed their usual functions; and M. le Gallois has adduced no proof whatever of its being of a different nature. The experiment, indeed, in which he lessens the extent of the circulation by ligatures, and thus en- ables the heart to support it after such a portion of the spinal marrow is destroyed, as would other- wise have destroyed it, is a sufficient refutation of his own opinion. It proves that the effect of crushing a large portion of the spinal marrow is merely that of enfeebling, not changing the nature of the action of the heart. Another position of M. le Gallois admitted by the Committee which does not seem to be war- ranted by his experiments is, that the power, on 59 which all the motions of inspiration depend, has its seat near that part of the medulla oblongata, which gives rise to the eighth pair of nerves. On this subject I shall hereafter have occasion to make many observations; and shall only observe here that inspiration is a complicated func- tion; and that if any of the powers essential to it is withdrawn, its most essential motions are as quickly destroyed as if all these powers had ceased. Now M. le Gallois made no experi- ments to ascertain whether it is by the destruction of one or all of these powers, that inspiration is destroyed by destroying this part of the medulla oblongata. The argument employed by the Committee in favour of M. le Gallois' opinions from the exist- ence of acephalous foetuses, is wholly invalidated by the fact, that foetuses have been born alive without either brain or spinal marrow; for in- stances of which M. le Gallois himself refers in the two hundred and fifty-first page of his Trea- ^jse to the Hist, de VAcad. des Sciences An. 1711, Obs. Anat. 3, and An. 1712, Obs. Anat. 6, but without attempting to shew how it is pos- sible to reconcile his opinions with the existence of such cases. An inconsistency of great importance in M. le Gallois' work, which he makes no attempt to explain, is overlooked by the Committee. He observes, in the commencement of his work, 60 « Ce que j'y ai dit du Coeur pouvant s'appliquer aux autres organes des fonctions involuntaires, la question peut etre consideree plus generale- ment, comme la determination du siege du prin- cipe qui preside a cet ordre de fonctions."* Yet he shews that decapitation does not influence the function of the heart, while the division of the eighth pair of nerves injures that both of the lungs! and stomach. It appears from what has been said, as far as I am capable of judging, that the experiments of M. le Gallois do not warrant any of the foflow- ing positions stated by the Committee as the re- sult of his experiments. "1° Que le principe de tous les mouvemens in- spiratoires a son siege vers cet endroit de la moelle allongee qui donne naissance aux nerfs de la huitieme paire; (i 2° Que le principe qui anime chaque partie du corps reside dans ce lieu de la moelle epiniere duquel naissent les nerfs de cette partie; " 3° Que c'est pareillement dans la moelle epi« niere que le coeur puise le principe de sa vie et de ses forces; mais dans cette moelle toute entiere, et non pas seulement dans une portion circon- scrite; "4° Que le grand sympathique prend nais- * Avant-propos. page 1. 11 speak here of the functions of the lungs themselves. not of the muscles of inspiration1. u sance dans la moelle epiniere, et que le carac- tere particulier de ce nerf est de mettre chacune des parties, auxquelles il se distribue sous l'influ- ence immediate de toute la puissance nerveuse f9 that is of the whole of the spinal marrow, which M. le Gallois regards as the seat of the nervous influence. If these results are not legitimate inferences from the experiments of M. le Gallois, the expla- nations of the long contested points respecting the action of the heart, founded on them, are inadmis- sible ; namely, That the heart is supplied with nerves because it derives its power from the spi- nal marrow; That it is influenced by the pas- sions, because the brain acts upon it through the spinal marrow; That it does not obey the will, because no organ influenced by every part of the nervous power, that is of the spinal marrow, does obey the will; (it may here be remarked, that were this position admitted, it would by no means explain why the motions of the heart are inde- pendent of the will, though influenced by the pas- sions,) and, That the circulation continues in acephalous and decapitated animals, because its direct dependence is not on the brain, but on the spinal marrow. If the foregoing observations are correct, we must dissent from the following opinion of the Committee. " Ces resultats resolvent sans peine toutes les difficultes qui se sont elevees depuis 62 Haller sur les causes des mouvements du coeur." The experiments of M. le Gallois indeed, by as- certaining some facts of great importance, while others immediately connected with them escaped his observation, have left the subject in greater confusion than he found it. Instead of removing the difficulties which formerly existed, the valu- able additions which he has made to our know- ledge have shewn us others. The heart's being subject to the passions, yet independent of the influence of the brain, on which so much has been written, does not seem to imply a more direct contradiction, than that the destruction of the same part of the spinal mar- row should, according to the way in which it is effected, either destroy the function of the heart, or little, if at all, influence it. I have had occa- sion to observe that M. le Gallois' explanation of this apparent contradiction is not a legitimate in- ference from his experiments; and I shall soon relate some, so simple that it is impossible to be deceived in their result, which seem directly to re- fute that explanation. Why, if the power of the heart depends on the spinal marrow, as it appears to do from the ex- periments of M. le Gallois, the accuracy of which I have ascertained by repeated trials, have foetuses been born alive where no spinal marrow had ever existed? Why, if the power of the heart depends on the 63 spinal marrow, does it continue to perform its usual motions after it is removed from the body ? Why, if (as M. le Gallois maintains, and it is generally admitted,) the various organs of invo- luntary motion bear the same relation to the ner- vous system, is the function of the heart uninflu- enced by decapitation, and that of the stomach immediately impaired by dividing or throwing a ligature round the eighth pair of nerves ?. Why does respiration cease on the destruction of a certain part of the medulla oblongata, since the nerves of the diaphragm and intercostal mus- cles arise from the spinal marrow, which M. le Gallois has proved to be capable of exciting the muscles independently of the brain ? He consi- ders this subject at length in the thirty-fifth and following pages of his treatise, and admits that he can give no explanation of it, calling it " one of the great mysteries of the nervous power, the discovery of which will throw the strongest light on the mechanism of the functions of that wonder- ful power." These apparent contradictions, it is evident, as well as those which existed before the discoveries of M. le Gallois, must be reconciled before we can be said to understand the relation which the thoracic and abdominal viscera bear to the ner- vous system. The doctrine which cannot recon- cile them must be erroneous. PART II. Experiments made with a view to ascertain the laws of the vital functions. The sanguiferous system, it is evident, may be divided into three parts, whose functions dif- fer ; the heart, the vessels of circulation, and the vessels of secretion. In the following Inquiry I shall, in the first place, endeavour to ascertain the principle on which the action of the heart and the vessels of circulation depends, and the relation which subsists between them and the nervous system. I shall then consider the principle on which the action of the muscles of voluntary mo- tion depends, and the relation which they bear to this system. The comparative effects of stimuli, applied to the brain and spinal marrow, on the heart and muscles of voluntary motion, will next be considered. An account of the experiments on these branches of the subject, though not in the order in which they are here related,* was pre- sented to the Royal Society in two papers, com- posed while I was still engaged in the Inquiry, * The experiments which I have since made have led to conclusions which render a different arrangement neces- sary. 65 and published in the Philosophical Transactions of 1815. The next object of inquiry will be the principle on which the action of the secreting vessels de- pends, and the relation which they bear to the nervous system. I shall then endeavour to ascer- tain the principle on which the action of the ali- mentary canal depends, and the relation which it bears to this system. These subjects will lead to some experiments and observations on the use of the ganglions, the nature of the nervous influ- ence, and the cause of animal temperature. I shall then consider the relation which the differ- ent functions of the animal body bear to each other, and the order in which they cease in dy- ing ; and the Inquiry will conclude with a review of the inferences obtained from the various expe- riments and observations which will be laid be- fore the reader, and some remarks on their appli- cation to explain the nature and improve the treat- ment of diseases. U 66 CHAP. I. On the principle on which the action of the heart and vessels of circulation depends. As it is now generally admitted by Physiolo- gists, as appears from the report just laid before the reader, that the heart is capable of perform- ing its functions after the brain is removed, the first question which presents itself is, how far does the power of this organ depend on the influ- ence of the spinal marrow, from which, we have seen, M. le Gallois maintains, that it is wholly derived. Exp. 1. A rabbit was deprived of sensation and voluntary power by a blow on the occiput. When the rabbit is killed in this way, the respi- ration immediately ceases ; but the action of the heart and the circulation continue, and may be supported for a considerable length of time by ar- tificial respiration, as practised by Fontana, and since by Chirac, Mr. Brodie, M. le Gallois, and others.* This mode of destroying the sensibility * It appears from the first volume of the Philosophical Transactions, that Mr. Hook, in the year 1667, shewed in the presence of the Members of the Royal Society, not only that the Ufe of a dog could be preserved for an hour after the thorax had been opened, and a great part of the dia- phragm removed, by alternately inflating the lungs and ah 67 does not influence the result of the experiment, and has the double advantage of preventing the animal's sufferings, and his motions. Its greatest inconvenience is, that if the blow is very severe, considerable vessels are sometimes ruptured, and there is almost always some rupture of vessels, which of course tends to impair the vigour of the circulation. In the present experiment, the circulation was supported by artificial respiration. The spinal marrow was laid bare from the occiput to the be- ginning of the dorsal vertebrae. The chest was then opened, and the heart found beating regular- ly, and with considerable force. The spinal mar- row, as far as it had been laid bare, was now wholly removed, but without in the least affect- ing the action of the heart. After this, the artifi- cial respiration being frequently discontinued, we repeatedly saw the action of the heart become languid, and increase on renewing it. The skull was then opened, and the whole brain removed, so that no part of the nervous system remained above the dorsal vertebrae, but without any abate- ment of the action of the heart, which still conti- nued to.be more or less powerful, according as lowing them to collapse so as to imitate respiration j but that the effect is nearly the same if the lungs are preserved in a state of permanent distension, by air constantly thrown into them, and allowed to escape by small perforations made in their surface. 68 we discontinued or renewed artificial respiration. This being for a considerable time discontinued, the ventricles ceased to beat about half an hour after the removal of the brain. On renewing the respiration, however, the action of the ventricles was restored. The respiration was again discon- tinued and renewed, with the same effects. Exp. 2. A rabbit was made insensible by re- moving part of the skull, and applying opium to the brain. The spine was then opened between the cervical and dorsal vertebrae. We then laid open the thorax, and supported the action of the heart by artificial respiration. The force with which it beat was carefully observed, and the spinal marrow destroyed by running a small hot wire up and down the spine, through the open- ing made in it, by which the action of the heart was not at all affected. Exp. 3. In the foregoing experiments, it may be said, there was no direct proof of the continu- ance of the circulation after the spinal marrow was destroyed or removed. On this account se- veral of the following experiments were made. A rabbit was deprived of sensation by a blow on the occiput, and the circulation supported by arti- ficial breathing. The carotids being exposed were seen beating. The cervical part of the spi- nal marrow was then destroyed by a hot wire, after Which the carotids were still found perfect- ly round and beating. 69 Exp. 4. In a rabbit rendered insensible by a blow on the occiput, the whole spinal marrow was destroyed by a hot wire, and the breathing artificially supported. One of the carotid arte- ries was then laid bare. Its beating was evident, and on dividing it, florid blood flowed from it freely. Exp. 5. The only difference between this and the last experiment was, that artificial breathing was not performed. In both, the spinal marrow was destroyed, by introducing a wire hot enough to make a hissing noise through an opening be- tween the cervical and dorsal vertebrae, first through the upper portion into the brain, then through the under portion to the end of the spine. On laying open one side of the neck, the carotid artery was found beating. On dividing it, blood of a much darker colour than in the former expe- riment was thrown out copiously per saltum. Exp. 6. A rabbit was rendered insensible by a blow on the occiput, and artificial respiration maintained. The spinal marrow from the base of the skull' to the beginning of the dorsal verte- brae was removed, and the remaining part of it destroyed by a hot wire. The carotid artery was then found beating, and, on dividing it florid blood rushed out with great force per saltum. Exp. 7- This experiment resembled the last, except that the spinal marrow, instead of being partly removed, was wholly destroyed by a hot 70 wire, and artificial breathing was not performed previous to opening the carotid, from which dark coloured blood flowed per saltum. We then in- flated the lungs, and florid blood soon began to flow copiously from the vessel, and appeared like a red stream mixing with the dark coloured blood which had previously come from it. This ex- periment was repeated in the same manner, and with the same result. Exp. 8. In this experiment the rabbit was ren- dered insensible, but not motionless, by the blow on the occiput, so that the breathing still conti- nued. The spine was opened, and the spinal marrow destroyed, as in the preceding experi- ment. The wire was used very hot. On intro- ducing it through the spine into the brain, the breathing immediately ceased. The femoral artery was laid bare about two or three minutes after respiration had ceased. The beating of the artery was evident. On opening it, a dark co- loured blood flowed from it freely. We now had recourse to artificial respiration. When it had been employed for about half a minute, the blood, which continued to flow copiously from the artery, became of a highly florid colour. The other femoral artery was then opened, from which florid blood also flowed freely. When about an ounce of blood had flowed from the two vessels, the inflation of the lungs was discontinued, and the blood again flowed of a dark colour. On 71 renewing the inflation of the lungs, the blood, in less than half a minute, again became of a florid colour. It continued to flow from the femo- ral arteries altogether for seven minutes. Three minutes after the blood had ceased to flow from them, the artificial respiration being continued, one of the carotid arteries was opened, from which a florid blood flowed in a free stream, to the amount of a dram and a half. The flow from the carotid artery ceased in eleven minutes after the femoral artery had been opened. Most of the blood was now of course evacuated. A good deal had been lost in opening the spine, which always happens. The left auricle and ventricle were found nearly empty. The blood which remained in them was florid. The right auricle and ventricle were full of dark blood. Exp. 9. From various trials, we found that in such experiments the circulation ceases quite as soon without, as with the destruction of the spinal marrow. Loss of blood seems to be the chief cause which destroys it. If the animal were operated upon without being rendered insensible, pain would also contribute to this effect. We frequently, after laying open the skull and spine, found the circulation lost before either the brain or spinal marrow had been disturbed. The cir- culation is particularly apt to fail, if artificial respiration is not carefully performed after the animal ceases to breathe. In making such ex- 72 periments, after opening the bone, it is always necessary to ascertain whether the circulation continues, before we destroy or remove the brain or spinal marrow. As little blood is lost in this part of the operation, when the carotid arteries are beating before, we always find them beating after it. The result of this experiment is still more striking in cold blooded animals, in which death takes place so slowly, that the circulation continues long after the total destruction of the brain and spinal marrow. • * Exp. 10. The brain of a frog and the spinal marrow, as low as the dorsal vertebrae, were laid bare. The thorax was then opened, and the heart found acting vigorously; and from the transparency of its sides, the passage of the blood through it distinctly seen. The part of the spi- nal marrow which had been laid bare was then removed, but without at all affecting either the motion of the heart, or the passage of the blood through it. The brain was then removed, with the same result. Exp. 11. The brain and spinal marrow of a frog were removed at the same time. On open- ing the thorax, the heart was "found performing the circulation freely. It appears from these experiments that the ac- tion of the heart is as independent of every part of the spinal marrow as of the brain; and, con- sequently, that the opinion of M. le Gallois that 73 it derives its power from that organ, and parti- cularly from the cervical part of it, must be re- garded as erroneous. I shall soon have occasion to consider the facts which led M. le Gallois to this opinion; we shall find, I think, that they admit of a very different explanation. We are now to inquire whether the action of the vessels of circulation is also independent of the brain and spinal marrow. The following experiments, and some others which I shall have occasion to relate, were made on the capillaries of the frog, which, from the ex- tent and transparency of the web of its hind feet, and from its great tenacity of life, appeared the best subject for such experiments. It has been questioned, how far inferences drawn from ex- periments made on cold blooded animals, can be supposed to apply to those of warm blood. Both Fontana and Dr. Monro observe, that in their experiments they found the system of both obey- ing the same laws. The experiments I have had occasion to make on both sets of animals tend to confirm this observation. There are certain cir- cumstances in which they evidently differ, in all others they seem to agree. As there is no part of the warm blooded animal on which such ex- periments on the vessels of circulation, as I shall have occasion to relate here and in the next chapter, can be made except tlie mesentery, many 74 of them would be attended with much greater suf- fering in this, than in the cold blooded animal.— Some of them, from the warm blooded animal being less tenacious of life, could not be so sa- tisfactorily performed on it. Exp. 12. A strong ligature was thrown round the neck of a frog, and the head cut off without any loss of blood; much loss of blood immedi- ately destroys the circulation in the extremities. The spinal marrow was then destroyed by a wire. On bringing the web of one of the hind legs before the microscope, I found the circula- tion in it vigorous for many minutes, and in all respects resembling that in the web of a healthy frog. This experiment was repeated with the same result. Exp. 13. The spinal marrow of a frog was destroyed, by moving, in various directions, a wire introduced into the spine by a hole made in the lowest part of it, and passed up into the brain. The animal was immediately deprived of sensibility and voluntary motion, and appear- ed to be quite dead. After it had lain in this state for several minutes, part of the web of one of the hind legs being brought before the microscope, the blood was seen circulating in it as rapidly as in the web of a healthy frog. In making such experiments it,is necessary to be aware, that handling and stretching the web tends to impair the vigour of the circulation in it. If this expe- 75 riment is objected to on account of its being made on an animal of cold blood, I may, as far as the larger vessels are concerned, refer to several ex- periments just related, in which the carotid and femoral arteries of rabbits were found beating and performing the circulation after the sensi- bility had been destroyed by a blow on the head, and the spinal marrow had been removed or destroyed. It appears from these experiments that the vessels of circulation, like the heart, retain their power after the brain and spinal marrow'are de- stroyed or removed, for it will hardly be main- tained, that in these instances the power of the heart supports the motion of the blood in the vessels. Should this opinion be maintained, the reader will find it refuted, respecting animals of cold blood, by experiments related in the next chapter, and respecting animals of warm blood, by those related in chapter tenth. From the whole of the foregoing experiments we must infer, that the position by which M. le Gallois explains why the destruction of the same portion of the spinal marrow destroys the circu- lation if suddenly effected, but fails to do so if effected slowly, is erroneous.* ' Does it not seem a necessary inference, from the experiments related in this chapter, that the action * See page 54. et seq. 76 of the heart and vessels of circulation depends on a power inherent in themselves, and having no direct dependence on the nervous system ? yet many facts, laid before the reader in the first part of this Inquiry, prove that a certain relation sub- sists between the nervous and sanguiferous sys- tems. What this relation is we are now to in- quire. CHAP. II. On the relation which subsists between the heart and vessels of circulation, and the nervous sys- tem* It is generally admitted, we have seen, that the action of the heart cannot be influenced by stim- uli applied to the brain and spinal marrow : and it seems almost a contradiction to suppose that it should be so, when we see that it cannot be in- fluenced by the total removal of these organs. There were many reasons, however, which induc- ed me to try the effect on the heart of stimuli so applied to the brain and spinal marrow, as not to excite any of the muscles of voluntary motion, whose action, both by throwing more blood to wards the heart, and by agitating the animal, prevents our judging of the effect of the stimulus. 77 Exp. 14. A rabbit was deprived of sensation and voluntary motion by a blow on the occiput, the action of the heart supported by artificial res- piration, and the brain and cervical part of the spinal marrow laid bare. The thorax was now opened, and the action of the heart, which beat with strength and regularity, observed. Spirit of wine was then applied to the spinal marrow, and a greatly increased action of the heart was the consequence. It was afterwards applied to the brain with the same effect. The increase of motion was immediate and decided in both cases. We could not perceive that it was greater in the one case than the other. Exp. 15. The foregoing experiment was re- peated, with the difference, that the whole of the spinal marrow was laid bare. The motion of the heart Was nearly, if not quite, as much influenced by the application of the stimulus to the dorsal, as to the cervical portion of the spinal marrow ; but it was very little influenced by its application to the lumbar portion. Exp. 16. In this experiment, only that part of the brain which occupies the anterior part of the head was laid bare. The rabbit in other re- spects was prepared in the same way as in the preceding experiments. The spirit of wine ap- plied to this part of the brain, produced as decid- ed an effect on the motion of the heart as in those experiments. The spirit of wine was washed off, 78 and a watery solution, first of opium, then of to- bacco, applied, with the effect of an increase, but a much less increase of the heart's action than arose from the spirit of wine. The increased ac- tion was greater from the opium than from the to- bacco. The first effect of both was soon succeed- ed by a more languid action of the heart than that which preceded their application to the brain. This effect was greatest, and came on soonest when the tobacco was used, and we always, for we frequently repeated the experiment, saw an evident increase in the action of the heart when we washed off the tobacco. We could also per- ceive this, though in a less degree, when the opi- um was washed off. Little or none of this debili- tating effect was observed when the spirit of wine was used. After its stimulating effect had sub- sided, the action of the heart only returned to about the same degree as before the application of the stimulus. Exp. 17- The foregoing experiment was re- peated on an animal of cold blood. Mr. Hast- ings had found, that immersing the hind legs of a frog in tincture of opium, in less than a minute deprives it of sensibility. This does not arise from any action of the opium ; a watery solution of opium, we found, however strong, does not produce the effect. It is immediately produced by simple spirit of wine, and arises from the ac- tion of the spirit on the nerves of the part to which 79 it is applied, for it takes place quite as readily as in the healthy frog, after a ligature has been thrown round all the vessels attached to the heart. It is remarkable, that if simple spirit of wine is used, the animal expresses severe pain; if tinc- ture of opium, very little. I have already men- tioned the reason why it is necessary, in order to judge of the result of this experiment, that the animal should be rendered insensible. fExp. li.J Having thus deprived a frog of sensibility, we laid bare the brain and spinal marrow, and open- ed the chest. The heart was found contracting with vigour. Spirit of wine was then applied to the spinal marrow, with an immediate and evident increase of the action of the heart. It was then applied to the brain with the same ef- fect. Watery solutions of opium and tobacco were also applied to both, with precisely the same effect as in the rabbit. The increase of action from the opium and tobacco was much less than from the spirit of wine, and was soon followed by a great diminution of action. The increase of action was least, and the diminution greatest from tobacco. On washing off the opium and tobacco with a wet spohge, the heart imme- diately beat more strongly. The different parts of this experiment were frequently repeated with the same result. It is remarkable that we could affect the motion of the heart by stimuli applied to the brain and spinal marrow, after they had all 80 ceased to produce any effect on the muscles of voluntary motion through the medium of the ner- vous system. Exp. 18. This experiment only differed from the last in the cervical part of the spinal marrow and lower part of the brain being removed, and the stimuli applied only to that part of the brain which lies between the eyes of the frog. Spirit of wine, opium and tobacco, thus applied, af- fected the motion of the heart quite as much, and precisely in the same way, as when they were applied to the entire brain or spinal marrow. When opium and tobacco were applied to the lower part of the spinal marrow, the motion of the heart appeared to be hardly at all affected by them. It was evidently increased when spirit of wine was applied to the same part. We found in the foregoing experiments, that considerable pressure either of the brain or spinal marrow produced little or no effect on the action of the heart. Its action could be influenced by agents applied to the brain and spinal marrow long after the circulation had ceased. Thus we see that the heart, although its power is independent of the brain and spinal marrow, is capable of being influenced through these organs. All that has been said of the power of the heart is strikingly illustrated by the following experi- ments. 81 Exp. 19. If the head and spinal marrow of a frog be removed, we have seen, the heart con- tinues to perform its function perfectly for many hours, nor does it seem at all immediately affect- ed by their removal. But we find the effect very different when the most sudden and powerful agent is applied to them. If they are even de- stroyed by being cut to pieces, the heart after their destruction beats just as before it. But if either the brain or spinal marrow be instantly crush- ed, the heart immediately feels it. The thorax of a large frog was laid open, and the motion of the heart observed, which performed the circula- tion perfectly, and with great force. The brain was then crushed by the blow of a hammer. The heart immediately performed a few quick and weak contractions. It then lay quite still for about half a minute. After this its beating re- turned, but it supported the circulation very im- perfectly. In ten minutes its vigour was so far restored that it again performed the circulation with freedom, but with less force than before the destruction of the brain. An instrument was then introduced under the heart, and after ascertaining that this had produced no change on its action, the spinal marrow was crushed by one blow, as the brain had been. The heart again beat quick- ly and feebly for a few seconds, and then seemed wholly to have lost its power. In about half a minute it again began to beat, and in a few mi- 13 82 nutes acquired considerable power, and again supported the circulation. It beat more feebly, however, than before the spinal marrow was de- stroyed. It ceased to beat in about an hour and a half after the brain had been destroyed. In another frog, after the brain and spinal marrow had been wholly removed, the heart beat nine hours, gradually becoming more languid. In this experiment we see that the heart not only retains its power long after the brain and spinal marrow are removed, but that if they are destroyed in such a way as to impair and almost destroy the action of the heart, it can recover the power of performing its function, after they no longer exist; precisely as a muscle of voluntary motion will by rest recover its excitability, al- though all its nerves are divided. Exp. 20. The foregoing experiment cannot be performed in the same way on warm blooded ani- mals, but it may be performed in a way equally satisfactory. In two rabbits the brain was crush- ed by a blow. In both the heart immediately beat with an extremely feeble and fluttering mo- tion. The anterior part of the brain only was crushed in another rabbit, with the same result. A strong ligature was thrown round the neck of a fourth rabbit, and at the moment it was tighten- ed, the head was cut off. The bleeding was re- strained by the ligature, except from the vessels defended by the bone. General spasms made the 83 body hard for the space of between one and ,two minutes, so that the beating of the heart could not be felt. At the end of this time, the heart was felt through the side, both by Mr. Hastings and myself, beating regularly, and not more quickly than in health. All the rabbits used in this ex- periment were of the same age. Exp. 21. The following experiment is still more conclusive. The anterior part of the brain of a rabbit was crushed by a blow. The side was rendered hard by a spasm for about half a minute. Neither during this, nor after it, could I perceive any motion of the heart by applying the hand to the side. The head was then cut off, about three quarters of a minute after the brain had been crushed. No blood spouted out, and very little ran from the vessels. A strong ligature was pass- ed round the neck of another rabbit of the same age. It was suddenly tightened, and the head cut off. In this instance little spasm took place, and the heart was found beating regularly under the finger for about three quarters of a minute. At the end of this time the ligature was slackened, and the blood spouted out to the distance of three feet, and continued to spout out with great force, till nearly the whole blood was evacuated. Exp. 22. From the strength of the spine of a rabbit, and the situation of the neighbouring parts, it is impossible to crush it, without directly influ- encing the state of the heart by the blow. We 84 opened it between the cervical and dorsal verte- bra, and suddenly forced a steel rod, of conside- rable thickness, through the cervical part. As in the experiments of M. le Gallois, the action of the heart was immediately debilitated. In the preceding experiments, the reader has seen, we repeatedly, slowly destroyed, or removed entire- ly, both the cervical and other portions of the spi- nal marrow, without at all influencing the action of the heart. These experiments point out an easy solution of the difficulties mentioned by M. le Gallois in the 119th and following pages of his treatise. When the greater part of the spinal marrow was destroyed by small portions at a time, compara- tively little effect was produced on the heart; but when a considerable part of it was crushed at once, the power of the heart was so impaired, that the circulation ceased. Thus in other cases, where the injury was inflicted slowly, and where it was inflicted suddenly, the result was found to be different. He observes, that if the spinal mar- row be divided near the occiput, and a certain part of it immediately destroyed, the circulation ceases. If some time intervene between the divi- sion and the destruction of precisely the same part, the circulation is not interrupted. In M. le Gallois' experiments, the .spinal mar- row was always crushed by a stilet, of precisely the same dimensions with the cavity of the spine. 85 In the experiments above related, the spinal mar- row was either removed, or destroyed by a com- paratively small wire, moved about in it till its functions ceased. The reader will easily under- stand, from what has been said, why this appa- rently slight circumstance occasions so essential a difference in the result of the experiments. We have just seen the difference of the result when any portion of the spinal marrow is suc- cessively destroyed by parts, or crushed at once, and when the brain is crushed at once or wholly removed. M. le Gallois maintains, we have seen, that affections of the brain influence the heart only through the medium of the spinal marrow. But in experiment 18th, we have seen, that after the lower part of the brain and the spinal marrow of a frog had been removed, agents applied only to that part of the brain which lies between the eyes, affected the action of the heart as much as when applied to the brain, while both this organ and the spinal marrow were entire. To remove any objection which may arise from the subject of this experiment having been an animal of cold blood, the following was made. Exp. 23. I divided the spine of a rabbit near the head, (which by stopping the respiration de- prived the animal of sensibility and voluntary power,) and then at the lower end, and by means of a wire, introduced at these parts, destroyed 86 the spinal marrow. Spirit of wine was then ap- plied to the brain, which influenced the action of the heart as readily, and to as great a degree, as it does when the spinal marrow is entire. We are now to inquire how far the vessels of circulation are capable of being influenced through the brain and spinal marrow. In order to ascertain whether the vessels can be stimulated through these organs independently of their action on the heart, it is neeessary in the first place to determine how far the vessels can support the motion of the blood independently of the heart. M. Bichat fRecherches Phys. sur la vie et la mort.J has shewn that in a frog the motion of the blood continues in the capillaries after the heart no longer propels it. This observation, indeed, we shall afterwards find applies to the warm, as well as the cold blooded animal. Exp. 24. A ligature was thrown round all the vessels attached to the heart of a frog, and the heart was then cut out. On bringing the web of one of the hind legs before the microscope, the circulation in it was found to be vigorous, and continued so for many minutes ; at length gradu- ally becoming more languid. In endeavouring to proceed further, I found much difficulty. It was not only necessary, in order to ascertain the effect of stimuli applied to 87 the brain of spinal marrow on the vessels of the web, to remove the heart, and to lay open the cra- nium, but also to prevent the voluntary motions of the animal, which continually occur, and never fail to accelerate the motion of the blood in the web. Exp. 25. A frog was deprived of sensibility and voluntary motion, by the upper parts of the body being immersed in laudanum; part of the cranium was then removed, after a ligature had been thrown round the neck to prevent loss of blood. The thorax was now opened, and all the vessels attached to the heart included in a liga- ture. But, notwithstanding this experiment was repeatedly performed with the greatest care, the circulation by all these preparatory means was so enfeebled, that although the blood still moved in the web, it was in so irregular and uncertain a way, that I never could arrive at any positive conclusion respecting the effect of the stimulus applied to the brain. After many fruitless at- tempts, therefore, I abandoned this mode of mak- ing the experiment. Although the action both of the heart and the muscles of voluntary motion so influence the ef- fect of stimuli applied to the brain, on the circu- lation in the foot, that, without wholly preventing the effect of both, no conclusion can be drawn, it is evident that the action of the latter cannot in- 88 crease the effect of sedatives; and the sedative lessening the power of the heart will not affect the result of the experiment, if it be made on the web of the frog. We have just seen, that the total ceasing of the action of the heart does not, for a considerable time, affect the circulation in it. The following experiments appear to be decisive of the effect of the sedative, and of the stimulus, as far as this can be decisive, the action of the heart remaining. It is evident that the action of either stimulus or sedative is equally conclusive respecting the direct influence of the nervous sys- tem on the blood vessels. Exp. 26. Part of the cranium of a frog was removed, the web of one of the hind legs brought before the microscope, and the circulation in it observed. The animal was now rendered insen- sible by the immersion of the other hind leg in laudanum. The insensibility did not in the least affect the circulation in the web before the micro- scope. Spirit of wine was then applied to the brain with an evident increase of the velocity of the blood in the web. The same effect was pro- duced in a less degree by watery solutions of opium and tobacco. After the tobacco had been applied for about half a minute, the motion of the blood was much less rapid than before its appli- cation. On washing off the tobacco the velocity of the blood increased, and was again lessened 89 on applying it. This was repeated several times with the same effects. The following way of performing the experiment is equally conclusive. Exp. 27. A frog was rendered nearly insen- sible by having its back immersed in laudanum. A ligature was then thrown round the neck to prevent loss of blood, part of the cranium remov- ed, the web of one of the hind legs brought be- fore the microscope, and the circulation in it which was rapid, observed. A strong infusion of tobacco was then applied to the brain, with the effect of at first rendering the circulation more rapid. In about half a minute it became more languid, and soon stopped altogether. On the infusion of J;obacco being washed off, the cir- culation returned .and regained considerable vi- gour. . The tobacco was several times applied to the brain and washed off, with the same effects. I may observe, that when the circulation in the web had almost ceased after the tobacco had been washed off, its velocity,was immediately increas- ed on applying spirit of wine to the brain. Exp. 28. Analogous to what I had occasion to observe respecting the heart, I could never, either by chemical or mechanical agents, excite any irregular action in the blood vessels. Their actjnrf was only rendered more or less powerful. The irregular appearances in the circulation in the web of a frog's foot, mentioned by Dr. Thompson, Professor of Military Surgery in the 14 90 University of Edinburgh, in his Lectures on In- flammation lately published, and which he as- cribes to inflammation, may be observed in any case, if the vessels be at all compressed in apply- ing the foot to the microscope; and although they are not compressed, these appearances very gene- rally occur when the circulation begins to fail. The blood will then stop and go on at intervals, and move backwards and forwards in the same vessel. I have often watched the capillaries from the commencement of inflammation to its greatest height, when the part is about wholly to lose its vital power, in the mesentery of a rabbit, the web of a frog's foot, and the fins of fishes, with- out perceiving the least tendency to this irregular motion when the part viewed was so applied to the microscope as not to compress any of its ves- sels.* When the circulation fails without any morbid distension of the vessels, the motion of the blood in the small vessels is irregular before it stops altogether; when it. fails from morbid dis- tension of the vessels, which gives rise to the phenomena of inflammation, this irregularity is not perceived, the motion of the blood gradually becomes slower till it ceases altogether. The power of the blood vessels, like that of a * An account of these experiments is published in th*e in- troduction to the second part of my Treatise on Febrile Dis- eases, and a plate given representing the state of the vessels in the different stages of inflammation. 91 the heart, is capable of being directly destroyed through the medium of the nervous system. Exp. 29. The web of one of the hind legs of a frog was brought before the microscope, and while Mr. Hastings observed the circulation, which was vigorous, I crushed the brain by the blow of a hammer. The vessels of the web in- stantly lost their power, the circulation ceasing. In a short time the blood again began to move, but with less force. This experiment was re- peated with the same result. If the brain is not completely crushed, the blow increases the ra- pidity of the circulation in the web. Exp. 30. The spiue of a frog was laid open at the lower end, and a wire of nearly the same dimensions with its cavity, forced through it, as in M. le Gallois' experiments. The web of one of the hind legs was then brought before the mi- croscope, and the circulation in it was found to have wholly ceased. In another frog, as we have seen,* the spinal marrow was destroyed by introducing in the same way, and moving in various directions, a wire much smaller than the cavity of the spine. The frog soon appeared to be quite dead, but the circulation in the web was found to be vigorous. What are the simple results of the experi- * See Experiment 13. 92 ments related in this and the preceding chapter? The first set prove, that the power of the heart and vessels of circulation is independent of the brain and spinal marrow, for we find that the functions of the former organs continue after the latter are destroyed or removed, and that their removal is not attended with any immediate effect on the motions of the heart and vessels. The second set prove, that the action of the heart and vessels of circulation may be influenced by agents applied either to the brain or spinal marrow. It is as readily influenced by agents applied to the anterior part of the brain, as by those applied to the cervical part of the spinal marrow. This is what we should expect when we trace the origins of their nerves. If it be said that the results of these experi- ments imply a contradiction, that we cannot sup- pose the power of the heart and vessels to be wholly independent of the brain and spinal mar- row, and yet influenced by stimuli applied to them, the reply is, that such are the facts, of the truth of which any one may easily satisfy him- self. On a closer examination of the phenomena of the nervous system, we shall find other similar difficulties. The experiments of M. le Gallois prove, in the most satisfactory manner, that a principal function of the spinal marrow is to ex- cite the muscles of voluntary motion, and that it 93 can perform this office independently of the brain. It performs it after the brain is wholly removed, and its powers seem not at all immediately im- paired by the removal of the brain ; yet we con- stantly see injuries of the brain impairing the functions of the spinal marrow. We may re- move the brain, and the animal performs the va- rious motions of its limbs as well as before its re- moval. Yet an injury of the brain often deranges the function of the spinal marrow. Of this ap- parent inconsistency, M. le Gallois justly re- marks, that two facts well ascertained, however inconsistent they may seem, do not overturn each other, but only prove the imperfection of our knowledge. Whichever of the disputed opinions respecting the functions of the nervous system we adopt, the foregoing phenomena seem to imply a contradic- tion. The experiments related in the following chapter point out still another instance of this ap- parent contradiction, and seem to suggest the principle on which it as well as the others depend. 94 CHAP. III. On the principle on which the action of the mus- cles of voluntary motion depends, and the re- lation which they bear to the nervous system. We are now to consider how far the principle on which the action of the muscles of voluntary motion depends, and the relation which they bear to the nervous system, resemble those of the heart and vessels of circulation. Exp. 31. By applying strong stimuli to the spinal marrow of a frog, strong and repeated con- tractions were excited in the muscles of the hind limbs, as long as the stimuli would produce the effect. On examining the state of the muscles of these limbs, I found them wholly deprived of their excitability. Now it is well known, that although all the nerves supplying the limbs of a frog be divided, and cut out close to the place where they enter the muscles, the latter still re- tain their excitability, which appears to be not at all less than when the nerves are entire. Lest it may be supposed that the nervous influence, which was exhausted in this experiment by stimu- lating the spinal marrow, still remains in the mus- cles after the nerves are divided, and thus pre- serves their excitability, the following experiment was made. 95 Exp. 32. All the nerves supplying one of the hind limbs of a frog were divided, so that it be- came completely paralytic. The skin was re- moved from the muscles of the leg, and salt sprinkled upon them, which, being renewed from time to time, excited contractions in theni for twelve minutes ; at the end of this time they were found no further capable of being excited. The corresponding muscles of the other limb, in which the nerves were entire, and of which consequently the animal had a perfect command, were then laid bare, and the salt applied to them in the same way. In ten minutes they ceased to con- tract, and the animal had lost the command of them. The nerves of this limb were nowr divid- ed, as those of the other had been, but the excita- bility of the muscles to which the salt had been applied was gone. Its application excited no con- traction in them. It sometimes happens, while the nerves of the limb are entire, that the volun- tary efforts of the animal prevent the contractions usually excited by the application of salt. This experiment was repeated in the same manner. and with a similar result. After the experiment, the muscles of the thighs in both linrbs were found to contract forcibly on the application of salt. It excited equally strong contractions on both sides. It is remarkable, that in this experiment, the excitability of the muscles whose nerves were en- 96 tire, was soonest exhaused. In the repetition of the experiment, this was the case to a still greater degree ; the muscles, whose nerves were entire, losing their excitability in about one half of the time required for exhausting the other. From this experiment it is evident, that the nervous influence, so far from bestowing excit- ability on the muscles, exhausts it, like other stimuli. The excitability, therefore, is a property of the muscle itself. Yet we have just seen, that it may be wholly destroyed by changes induced on the nervous system. On the same principle we explain the seeming contradiction respecting the action of the heart and vessels. We have seen that their power exists as independently of the brain and spinal marrow, as the action of the first muscles to which the salt was applied, Avhose nerves had been divided; but, while the brain and spinal marrow retain their functions, and the connection of nerves is entire, the heart and vessels, as well as the muscles of voluntary mo- tion, may be influenced by agents acting through the nervous system. It is not difficult to account for the latter muscles being more copiously sup- plied with nerves than the heart, because all the stimuli which affect them, act through their nerves, while the heart is only now and then in- fluenced through its nerves, its usual stimulus being as immediately applied to it, as the salt was to the muscles of the limb in the above ex- 97 periment, and acting as independently of the nervous system. We do not surely, in the ex- periments which have been laid before the reader, see any difference in the nature of the muscular power of the heart, and that of the muscles of voluntary motion, except their being fitted to obey different stimuli, a difference which we find in the two sides of the heart itself. It may here be objected, that in apoplexy the power of the muscles of voluntary motion is lost, while that of the heart is little, or not at all, im- paired. Were such the fact, this objection would be unanswerable; but I have repeatedly examin- ed the state of the muscles of voluntary motion in apoplexy, both in warm and cold blooded ani- mals, and found their excitability unimpaired. It is not their power, but the stimulus which excites them, that is lost in apoplexy. In this disease the heart continues to contract, because its stimulus is still supplied; the muscles of vo- luntary motion cease to contract, because their stimulus is withdrawn.* The conclusions afforded by the foregoing ex- periments so far agree with those of Haller, that they prove the heart and other muscles to pos- sess an excitability independent of the nervous system; but they prove, contrary to the opinion * See Chap. 10. 15 98 of that great Physiologist, that the heart is, equally with the muscles of voluntary motion, capable of being stimulated through this system. In the report of the National Institute of France, which has been laid before the reader, it is observed, u the adversaries of irritability have asked, why, if the nervous power has no action on the heart, is this organ supplied with nerves, and why it is so powerfully subjected to the in- fluence of the passions ? Haller never gave any satisfactory explanation of these objections, but every thing proves that he felt all their force." These objections, we have seen, prevented Hal- ler's doctrine of irritability from being generally admitted by Physiologists, and at length led M. le Gallois to suppose that he had wholly refut- ed it. We may, I think, trace the subject further. It has been shewn by direct experiment, by M. le Gallois, that the spinal marrow is capable of per- forming its functions independently of the brain, yet, as has been observed, the spinal marrow may be influenced through the brain. Thus the excitability of the spinal marrow bears the same relation to the brain, which that of the muscles bears to the spinal marrow and its nerves, and I would add all nerves distributed to muscles, some of which arise from the brain, but seem to bear precisely the same relation to the sensorium and to the muscles, with those which arise from 99 the spinal marrow. Even M. le Gallois, although his experiments lead to an opposite conclusion,* observes, that the brain seems to act on the spinal marrow as the latter does on the parts it ani- mates. We know the peculiar office of the brain, by observing what functions are lost by its re- moval, the sensorial functions. The nervous, then, obeys the sensorial system, in the same way in which the muscular obeys the nervous system; but as the muscular power has an existence inde- pendent of the nervous, so has the nervous an ex- istence independent of the sensorial power. I shall, towards the latter part of this inquiry, endeavour to point out with more precision than has been done, the line of distinction between the sensorial and nervous functions, which appears to me from direct experiments, to be very dif- ferent from that assumed by M. le Gallois.! * He infers from his experiments that the power of the heart ceases on the destruction of the spinal marrow, but that that of the spinal marrow remains after the destruction of the brain. t See Chap. 10. 100 CHAP. IV. On the comparative effects of stimuli applied to the brain and spinal marrow on the heart and muscles of voluntary motion. In making the experiments related in the pre- ceding chapters it was evident, that although the muscles of involuntary are equally with those of voluntary motion subject to the effects of stimuli applied to the brain and spinal marrow, the laws which regulate these effects on the. two sets of muscles are very different. The following ex- periments point out more precisely in what this difference consists. Exp. 33. Part of the cranium of a rabbit was removed, and a wire passed in various directions through the brain. I could not in this way in the least affect the muscles of voluntary motion, except when I made the wire approach those parts of the brain from which the spinal marrow and nerves originate. The muscles of voluntary motion were then thrown into violent spasms.— I sliced off the whole of the upper and anterior part of the brain without affecting the muscles of voluntary motion. The knife only excited their action when it approached the source of the nerves and spinal marrow. Exp. 34. Having deprived another rabbit of 101 sensibility and voluntary motion by a blow on the occiput, that I might be enabled to judge of the effects which a stimulus applied to the brain would produce on the heart, I removed part of the cranium and laid open the thorax. The heart was found beating regularly. By passing a wire through the brain in any direction, the beats of the heart were accelerated and rendered stronger. I could not perceive that this effect was produced more powerfully when the wire was directed to- wards the source of the nerves, than when any other direction was given to it, provided it passed through an equal portion of the brain. When an instrument was merely pressed on the surface of the brain, the effect was similar. When a pair of scissars, or any other thing of larger bulk than the wire was passed into the brain, the effect on the heart was greater than from the wire. It was still greater when the brain was wounded rapidly in many directions. Exp. 35. Part of the cranium of a rabbit was removed, and after passing a knife through the brain in various directions towards the origin of the nerves, which excited the strongest spasms in the muscles of voluntary motion, the blood being absorbed by a sponge, I applied strong spirit of wine to the surface of the brain, and dropt it into the cuts, without at all affecting the muscles of voluntary motion. The upper part of the brain was then wholly removed, and the 102 space filled with strong spirit of wine, but no spasms were excited in the muscles of voluntary motion. Exp. 36. Another rabbit was deprived of sen- sibility and voluntary motion by a blow on the occiput. Part of the cranium was then removed, the thorax laid open, and the heart found beating regularly. Spirit of wine was now applied to the surface of the brain, by which the frequency and force of the heart's beats were immediately increased. Several Cuts were then made in the brain, and the spirit of wine dropt into them, by which the action of the heart was increased in a much greater degree. Spirit of wine increased the action of the heart more than any mechanical injury, which never produced the strong action in this organ, that it does in the muscles of volun- tary motion. This experiment was repeated with a watery infusion of opium instead of spirit of wine; the result was in all respects the same, except that the action of the heart was less increased than by the spirit of wine. Under the term brain, I mean to include the cerebellum as well as cerebrum. From many trials on rabbits made to ascertain the point, I could not perceive that the heart is more or less affected either by chemical or mechanical stimuli applied to the cerebellum than to the cerebrum; nor are the muscles of voluntary motion affected 103 by wounding the cerebellum, except we approach the source of the spinal marrow and nerves. In some of my experiments, I thought that stimuli applied to the cerebellum affected the action of the heart rather more powerfully than when ap- plied to the cerebrum ; but this was contradicted by other experiments. Exp. 37. I repeatedly cut off the head of a rabbit close to the occiput. For some time the trunk and limbs were affected with violent spasms. The cut end of the spinal marrow was so sensible that the slightest touch of a wire, af- ter the spasms had subsided, immediately excited the action of the muscles of voluntary motion. The strongest spirit of wine and watery infusion of opium were applied to it, without producing the least effect on those muscles. The applica- tion, however, of stronger chemical stimuli, the nitric and muriatic acids, threw the muscles of the fore-legs into powerful contractions. Having deprived a rabbit of sensation and vo- luntary motion, in an experiment already related, I found that both spirit of wine and a watery in- fusion of opium applied to the spinal marrow, in- crease the action of the heart. Exp. 38. I found both in rabbits and frogs that, after all stimuli applied either to the brain or spinal marrow had ceased to produce any ex- citement in the muscles of voluntary motion, both chemical and mechanical stimuli so applied still 104 increased the action of the heart: the former more than the latter. Exp. 39. I tried, in every possible way, both by mechanical and chemical stimuli, and both before and after the sensibility was destroyed, to excite, through the brain or spinal marrow of rabbits and frogs, any irregular action in the heart which is so readily excited in the muscles of voluntary motion, but could not. Nor could I by sedatives, applied to the nervous system, occasion any irregular action in the heart. Its action was rendered quicker or slower, more or less frequent, stronger or weaker, but never ir- regular. The only instance in which irregular action was excited in the heart, was when its power was nearly destroyed by crushing the brain or spinal marrow. Exp. 40. I found from many trials both on rabbits and frogs, that the excitement of the mus- cles of voluntary motion took place chiefly at the time the stimulus was applied to the brain or spinal marrow. It was generally necessary to move the instrument; thus applying it to a new surface in order to support the effect. Repeated contractions of the muscles of voluntary motion will sometimes continue, assuming the form of a fit, as long as the instrument remains in the brain, although it be kept as still as the motions of the animal will admit of. The increased action of the heart on the contrary, could generally be ob- 105 served as long as the stimulus, whether chemical or mechanical, was applied, unless it was of a nature to produce the sedative, after the stimu- lant effect. The sedative effect is so far from being the consequence of the previous excite- ment as many physiologists have supposed, that spirit of wine and mechanical stimuli, which produced no sedative effect, but continued to stimulate the heart as long as they were applied, produced a much greater degree of excitement than tobacco, whose slight stimulant effect was quickly succeeded by a powerful sedative one. It appears from these experiments, that che- mical stimuli, applied to the brain and spinal marrow, exert a greater power over the heart than mechanical stimuli, while the latter exert a greater power over the muscles of voluntary motion than chemical stimuli; that both chemi- cal and mechanical stimuli, applied to the brain and spinal marrow, excite the heart, after they cease to produce any effect on the muscles of voluntary motion; that stimulating every part of the brain and spinal marrow equally affects the action of the heart, while the muscles of volun- tary motion are only excited by stimuli applied to the parts of those organs from which their nerves originate; that stimuli applied to the brain and spinal marrow never excite irregular action of the heart, while nothing can be more irregular than the action they excite in the mus- 106 cles of voluntary motion; that their effect on these muscles is felt chiefly on their first application, but continues on the heart as long as the stimu- lus is applied. These differences in the effects of stimuli applied to the brain and spinal mar- row on the muscles of voluntary, and those of involuntary motion, must be explained before we can be said to understand the relation which subsists between the nervous system and the heart. It appeared to me probable, from many expe- riments, that the cause of chemical stimuli, ap- plied to the nervous system, producing a greater effect on the heart than mechanical stimuli do, is, that the former, from their nature, act on a larger portion of the brain and spinal marrow. If this opinion be correct, the mechanical stimulus will be rendered the most powerful by confining the chemical to a smaller space than the mechanical stimulus occupies. Exp. 41. Both in frogs and rabbits I applied to various parts of the brain and spinal marrow, and particularly to those parts from which the nerves originate, minute portions of strong spirit of wine, without at all influencing the action of the heart. When these small portions were ap- plied to a great many parts, the heart began to beat more frequently. This of course was much the same thing as at once applying the spirit of wine to a larger part. We have seen in the fore- 107 going experiments, that mechanical stimuli ap- plied to any considerable portion of the nervous system, increase the action of the heart. It ap- pears from the following experiments that we cannot affect the heart by mechanical stimuli con- fined to any small part either of the brain or spinal marrow. Exp. 42. In a rabbit deprived of sensibility by a blow on the occiput, I wounded different small parts of the brain with a wire, particularly all those parts near which the nerves of the heart .appear chiefly to originate; but could not affect the motion of this organ, while at the same time passing the wire through any considerable por- tion of the brain immediately accelerated it. Exp. 43. I laid open the cervical part of the spine of a rabbit, rendered insensible by a blow on the occiput, and repeatedly passed the wire transversely through the spinal marrow, without being able at all to affect the motion of the heart; but on a wire being passed longitudinally, so as to bring it into contact with a larger portion of the spinal marrow, the motion of the heart was im- mediately accelerated. On the same principle, when the wire was made to wound many minute portions of the brain and spinal marrow in quick succession, the action of the heart was increased. In another rabbit, I divided the spinal marrow at the occiput without at all affecting the heart. Mr. Clift, in an account of experiments on the 108 carp, published in the Philosophical Transac tions for 1815, observes, that on dividing the spinal marrow at the occiput, the action of the heart was greatly accelerated for a few beats; but he divided the spinal marrow while the ani- mal retained the power of the muscles of volun- tary motion, which never fail to be called into action by wounding it, and whose action, by in- creasing the flow of blood, always accelerates the motion of the heart.* Thus we see that neither chemical nor me- chanical stimuli applied to the brain and spinal marrow, affect the action of the heart, unless they make their impression on a large portion of these organs. In the various experiments I have re- lated, every part of them was stimulated indi- vidually, without the action of the heart being in- fluenced ; and the stimulus being the same, the force with which it acted on this organ was al- ways proportioned to the extent of surface to which it was applied. I could not find that it was of any importance what part of the brain * It is particularly satisfactory to me that Mr. Clift, on repeating my experiment, in which the spinal marrow was destroyed by a hot wire, found the same result in the carp, which I had done in rabbits and frogs. He did not ascer- tain whether the circulation continued after the destruction of the spinal marrow, but from this occasioning little or no diminution in the action of the heart, we can have little doubt of the continuance of the circulation. 109 was stimulated. Even stimulating the surface alone, either mechanically or chemically, we have seen, immediately increased the action of the heart. The muscles of voluntary motion, on the contrary, it appears from the above experiments, are wholly insensible to stimuli applied to the brain, except near the origin of the nerves and spinal marrow. It is remarkable that while a rabbit perfectly retains its sensibility, and ex- presses great pain on any of the muscles being wounded, it exhibits no expression of pain from the brain being sliced, until the knife approaches the origin of the nerves or spinal marrow. Another circumstance, which appears to be of great importance in tracing the cause of the dif- ferent effects of stimuli applied to the brain and spinal marrow on the muscles of voluntary and involuntary motion, is, that the heart obeys a much less powerful stimulus than the muscles of voluntary motion do. We have seen that only the most powerful chemical stimulus affects them, while all that were tried readily influenced the action of the heart. Mechanical stimuli which, by bruising and dividing the parts, occasion the greatest possible irritation, are best fitted to ex- cite the muscles of voluntary motion. Chemical stimuli, indeed, from their effects on the heart, we should consider the most powerful. But their greater effect on this organ is readily explained by the influence of stimuli applied to the brain 110 and spinal marrow on the.heart, being propor- tioned to the extent of surface to which they are applied. It is evident that the stimulus can be applied to a greater extent of surface in the fluid than in the solid form. When the effect of the mechanical agent is rendered extreme, we find its influence on the heart far greater than that of any chemical agent I tried. From experiments related in the second chapter of this part, it ap- pears, that suddenly crushing any considerable portion of the brain or spinal marrow instantly destroys the power of the heart. The conclusions then at which we arrive are, that the heart is excited by all stimuli applied to any considerable part of the brain or spinal mar- row, while the muscles of voluntary motion are only excited by intense stimuli applied to certain small parts of them. • These facts being ascertained, the other differ- ences observed in the effects of stimuli applied to the brain and spinal marrow, on the heart and muscles of voluntary motion, are easily ex- plained. Irregular action of a muscle arises from sti- muli acting partially, or at intervals, on its nerves, or on the particular part of the brain or spinal marrow, from which its nerves arise. But very partial action of a stimulus on the brain and spi- nal marrow, we have just seen, is incapable of exciting the,heart, and while the stimulus is ap- Ill plied to any part of these organs, as all parts of them seem equally to influence the heart, it can- not act upon it interruptedly, as an instrument does on the muscles of voluntary motion when it is moved from place to place in the brain. When the instrument is kept still, after it is in- troduced into the brain, the action of the muscles of voluntary motion often ceases ; Its'merely be- ing in contact with the parts of the brain which excite these muscles, not being sufficient to call them into action. As the muscles of voluntary motion feel the impressions made on a very small part of the brain only, in proportion as this part is small, the impression must be great to affect them ; but the heart, which is influenced through all parts of it, though not very powerfully through any one, feels all the impressions made on this organ, provided they are made on a sufficiently extensive portion of it; thus, within certain li- mits, as long as the instrument remains in the brain, its stimulant effect on the heart continues. It is true, that although the heart is only influ- enced by agents applied to a large portion of the brain, we may conceive them so applied as to pro- duce irregular action in it, and we find that cer- tain irritations of the nervous system have this effect. But it is evident, that the heart not being subject to stimuli whose action is confined to a small portion of this organ, and being equally af- fected through all parts of it, must render it much 112 less subject to irregular action; which may be one of the final causes of the heart, whose regular action is of such importance in the animal econo- my, being made subject to the whole, and not to any one part of the brain ;* and readily accounts for our not being able to produce irregular action in it, in the above experiments. What has been said also explains why those, who have endeavoured to influence the heart by stimulating the parts of the brain from which its nerves seem chiefly to originate, have failed. When indeed the source of the nerves of the heart is considered, it will be found to derive its nervous influence from every part of the nervous system, and not very remarkably from any one part, a cir- cumstance which particularly corresponds with the result of the foregoing experiments. From the same facfs we explain, why the heart is stimulated through the brain and spinal marrow after their power is so far weakened as no longer to convey the effect of the stimulus to the muscles of voluntary motion. As these obey sti- muli applied to only one part of those organs, if the change in this part is not sufficiently strong to produce the effect, it cannot be assisted by any other. Thus I have found by experiment, that a * In the course of this inquiry another, and apparently more important reason will appear, why it is necessary that the heart should be subject to the influence of every part of the brain and spinal marrow. 113 blow which affects the brain generally, without materially injuring it, produces comparatively little effect on the muscles of voluntary motion, because no one part suffers greatly, but it produces a great effect on the heart, because it feels the sum of all the impressions. The nervous system, therefore, may be so far exhausted as not to ad- mit of the vivid impressions necessary to excite the muscles of voluntary motion, and yet capable of those which influence the heart. CHAP. V. On the principle on which the action of the ves- sels of secretion depends, and the relation which they bear to the nervous system. It not only appears from the experiments which have been laid before the reader, that the power of the heart and vessels of circulation is independent of the nervous system, but that that of the muscles of voluntary motion is so likewise, and that these like the former are only subjected to this system in the same way in which they are subjected to every other agent that is capa- ble of exciting them. Thus we find, that all the moving powers of the animal body, as far as we have hitherto traced them, are independent of the 17 114 nervous system, but that this system is equally capable of acting as a stimulus to them, although in different ways, whether they are subject to the influence of the will or not. Is the power of se- cretion also independent of, though influenced by, the nervous system? SECT. I. On the effect of withdrawing the nervous in- fluence from secreting surfaces. I was soon convinced that although the pow- ers of circulation are independent of the nervous system, those of secretion are very far from being so. M. le Gallois, in the treatise so frequently alluded to, enumerates many physiologists who divided the eighth pair of nerves; and he gives a minute account of the consequences of their division, particularly of those which he himself observed in rabbits and Guinea pigs. The chief are, oppressed breathing and loss of power in the stomach. Mr. Brodie also gives an account of experiments, in which he divided the eighth pair of nerves in dogs, in a paper published in the Philosophical Transactions for 1814. But the animals always died of oppressed breath- ing before he could judge of the effect on the stomach. He proved, however, by another set 115 of experiments, that arsenic introduced into the system after the division of the eighth pair of nerves, does not produce the copious secretion from the stomach and intestines which it is found to do under ordinary circumstances. He found a similar result when he divided the stomachic nerves immediately above the cardiac orifice of the stomach. The lungs are affected differently according to the part at which the nerve is divided. If, in the rabbit, it be divided before the inferior laryngal nerve is sent off, or this nerve itself is divided, great difficulty of breathing, with a croaking noise, immediately follows, arising, as M. le Gal- lois has shewn,* from the opening of the glottis becoming much narrowed as soon as the nerve is divided. If the eighth pair of nerves are divided below the place at which they send off this nerve, there is little or no dyspnoea for some time. Mr. Hastings, who watched the progress of the follow- ing experiments with great care, observed, that when the eighth pair of nerves were divided be- low the inferior laryngal nerve, the dyspnoea, al- * M. le Gallois says, that the difficulty of breathing comes on from dividing the recurrent nerves, but Mr. Hastings, who frequently performed the experiment, always found that there was little or no dyspncea induced in the rabbit by dividing the recurrent nerves. It was when he divided the laryngal nerves that the sudden dyspncea, mentioned by M. le Gallois, took place. 116 though it often came on sooner, was greatly in- creased by the attempts to vomit, which generally happened almost immediately after eating; but which, if the animal was not allowed to eat, fre- quently did not occur for an hour and a half, or two hours, after the division of the nerves. The dyspnoea increases, and the animal seems at last to die of it. The lungs are found after death dis- tended with a frothy fluid, which fills the bronchia and air-cells, and prevents the lungs collapsing; and they are covered with patches of a dark red colour, often of great extent, which give the ap- pearance of the vessels being greatly distended with blood, or of blood having escaped into the cellular substance. They appear of a more com- pact texture than healthy lungs, and sink in water. In short, the fluids of the lungs no longer undergo the proper change, but accumulate in the bronchia, air-cells and blood vessels. As M. le Gallois' account of the effects of the jdivision of these nerves on the stomach does not altogether agree with that of the authors, he quotes, and is also in other respects contradictory. Mr. Hast- ings frequently repeated the experiment on rab- bits, and sometimes with such dexterity, that the animal lived about twenty-six hours after the ope- ration. I had thus an opportunity of ascertain- ing, that even during this length of time, although the stomach was full of food, (parsley) no change on it had been effected. It continued in the same 117 state as when it left the mouth, simply divided by mastication, preserving perfectly both its appear- ance and its smell. It was impossible to distin- guish it from parsley chopped small with a knife. It occurred to me, that the pain and irritation occasioned by the operation might, in these ex- periments, have induced such a degree of disease as to destroy the powers of digestion, independ- ently of any specific effect on the stomach. I therefore requested Mr. Hastings to perform the experiment in the following manner. Exp. 44. Two rabbits of about the same age were fed in the same way. In both the eighth pair of nerves were laid bare. In the one rabbit they were divided ; in the other, after being rais- ed on a probe, they were replaced without injur- ing them. Both rabbits were allowed to eat as much parsley as they chose after the operation. When that in which the nerves were divided died, which did not happen for more than twenty hours after the operation, the other was killed. In the former the food was found wholly undi- gested ; in the latter the digestive process had gone on as usual, and the food was found in the same state as in a healthy rabbit. The stomach is generally distended to a great- er size than usual when the eighth pair of nerves have been divided. This happened in the pre- sent case. It is remarkable, that the oesophagus also is found full of food, and very much distend- 118 ed. From this circumstance, and from an experi- ment of M. le Gallois, in which one only of the eighth pair of nerves being divided in a Guinea pig, the animal survived several days, and the stomach became enormously distended with un- digested food ; I say, from these circumstances, it occurred to me, that the sensation by which an animal judges when he has received enough of food, being destroyed by the division of the nerves, the animals had perhaps occasioned over- distension of the stomach, and thus destroyed the power of digestion, for they often ate a great deal after the operation. I therefore requested Mr. Hastings to repeat the experiment, allowing the animal to eat as much as he chose before the ope- ration, but none after it. Exp. 45. This he did, but the result was the same. The food with which the rabbit had filled its stomach, just before the division of the nerves, remained wholly unchanged, and it was remark- able, that the oesophagus was just as much dis- tended with the food as when the animal had eaten after the operation. This arises from the fruitless efforts to vomit, which always come on in an hour or two after the division of the nerves.* * I have already mentioned that Mr. Hastings observed the dyspncea greatly increased by the fruitless attempts to vo- mit. As the oesophagus in the rabbit lies contiguous to the yielding part of the trachea, the distension of the former can- not fail to lessen the capacity of the latter. 119 It deserves notice, that although the eighth pair of nerves have been divided, the food is found covered with apparently the same semi-fluid which we find covering the food in a healthy sto- mach. These experiments seem to leave no room to doubt, that the office of the stomach is suspended by dividing the eighth pair of nerves. A simi- lar observation applies to the lungs. In the animal in which the eighth pair of nerves were merely raised on the probe, the lungs continued perfectly to perform their office, and were found of a healthy appearance after death. In all the instances in which these nerves were divided, great dyspnoea, we have seen, soon came on, and the air-cells and tubes were found clogged with frothy mucus. SECT. II. On the nature of the nervous influence. The discoverer of galvanism, from whom it takes its name, maintained, that it is the gal- vanic influence which is conveyed by the nerves, and to which we must ascribe the action of the muscles; and with many since his time it has 120 been a favourite opinion, that the nervous influ ence is allied to galvanism, if they are not the same thing. Nobody however, as far as I know, has at- tempted by experiments on the living animal, to ascertain how far galvanism is capable of per- forming the functions of this influence. To ascertain whether it possesses such powers, it is necessary to apply it to the fluids, as nearly as possible in the same way in which the ner- vous influence is applied; to try, for example, whether, Avhen the latter is withdrawn from a secreting surface, and the secreting power thus wholly destroyed, we can, by galvanism, restore this power, and enable the part to prepare the same fluid which the nervous influence had enabled it to prepare. We have seen, that by dividing the eighth pair of nerves, the power of digestion, and con- sequently the formation of gastric juice, is wholly lost, and the secreting power of the lungs de- ranged. This appeared to me to offer an excel- lent opportunity of making the experiments in question. It is not difficult, by coating the lower part of the divided nerves with tin foil, and ap- plying a small plate of metal to the skin over the stomach and lungs, to expose these organs, by means of a galvanic trough, to any degree of galvanic power which we may judge proper. 121 I explained my views to Mr. Hastings, and re- quested him to make the following experiment.* Exp: 46. The hair was shaved off the skin over the stomach of a young rabbit, and a shilling bound on it. The eighth pair of nerves were then divided, and about a quarter of an inch of the lower part of each coated with tin foil. The tin foil and shilling were connected with the op- posite ends of a galvanic trough, containing fifty- two four-inch plates of zinc and copper, the in- tervals being filled with muriatic acid and water, in the proportion of one of acid to seven of water. The galvanic influence produced strong contrac- .tion of the muscles, particularly of the fore limbs. For five hours the animal continued quite free from the symptoms which follow the division of the eighth pair of nerves in rabbits. It had nei- ther vomited nor been distressed with dyspnoea. It had not eaten any thing after the nerves were divided. At this time the power of the trough became much weaker, so that it produced no vi- sible effect on the muscles. The respiration now began to be disordered. In a quarter of an hour it became so difficult, that the animal appeared * From my dislike to make experiments on living animals, when I had occasion to make such experiments, I frequently requested my friends to perform the operative part; but I have related none the result of which was not observed by myself. 122 to be dying. It was gasping. Acid was put in- to the trough till the galvanic power became as great as at first. Soon after this the animal ceas- ed to gasp, and breathed with much greater free- dom. The galvanic process was several times discontinued and renewed, so that we repeatedly saw the gasping and extreme dyspncea return on discontinuing, and disappear on renewing it.— The animal died in six hours after the division of the nerves. On opening it we found the oesophagus perfect- ly natural, and no food in it. The stomach was not larger than usual. The food had undergone a considerable change. The appearance and smell of the parsley were gone. The smell was that of the rabbit's stomach while digestion is going on, which is peculiar. Both Mr. Hast- ings and myself, who have been much accustom- ed to examine the stomach of rabbits under vari- ous circumstances, thought that digestion was nearly as perfect as it would have been in the same time in a healthy rabbit. This rabbit had not eaten any thing for twelve hours till within three hours of the experiment; it was then very hungry, and was allowed to eat as much parsley as it chose. The membrane of the trachea was of its natu- ral colour, and there was no fluid in it. The ramifications of the bronchia in the left lung were quite free from frothy mucus. There was some 123 fluid in the right lung, though it did not appear much gorged, there was one dark spot on it.— The lungs collapsed imperfectly on opening the chest. I requested Mr. Hastings to make the experiment in the following manner. Exp. 47. Two full grown rabbits were kept without food for twelve hours: within half an hour of the experiment, they eat as much parsley as rabbits usually do at one time. After the hair was shaved off the region of the stomach in one of them, and a shilling bound upon it, the eighth pair of nerves were divided about eight o'clock in the morning, and each nerve coated with tin foil, to the extent of half an inch. Difficulty of breathing was evident immediately after the ope- ration. It was nine o'clock before the animal was brought properly under the galvanic influ- ence; till then the respiration was very much oppressed ; it soon improved on keeping up a regular and gentle twitching of the muscles of the chest and fore-legs. It appeared to us, that in the preceding experiment the animal had been exhausted by the galvanic influence. In this in- stance, we regulated its degree by the effect it produced, using the third, half, or whole of the trough, according to circumstances, regarding a gentle twitching of the fore-legs, as the measure of a due degree of the galvanic power. About ten o'clock the breathing became very laborious, ow- ing to the trough's not acting well; on increasing 124 the galvanic power the breathing became pretty free, although the animal still made a croaking noise in respiration, which continued more or less till its death. The cause of this I shall presently explain. The breathing always began to get worse when the galvanic power became too weak to produce any twitching in the fore-legs. At eight o'clock in the evening the animal seem- ed very composed, and breathed with considera- ble freedom, the trough having acted regularly for some hours. Notwithstanding it was kept in the lying position on its side, it now eat greedily some bits of parsley offered to it. The same quan- tity was at the same time given to the other rab- bit. There did not appear any increase of the difficulty of breathing, nor any disposition to vo- mit after taking the food. It was now about twelve hours since the nerves were divided, during which there had not been the least disposition to vomit. At about a quarter past ten, that is fourteen hours and a quarter after the nerves had been di- vided, the galvanic influence had become too fee- ble, and the animal made one attempt to vomit. The power of the trough was increased, and no further attempt to vomit took place. After this, however, the breathing became more laborious, and although it gradually improved very much, it could not be brought to its former state, the ani- mal continuing to gasp slightly. About twelve o'clock it had a violent return of dyspnoea, which, 125 from this time, to a quarter before one, increased rapidly. At one the animal died, having survived the division of the nerves seventeen hours. The other rabbit was killed at the same time. The stomachs of both were laid open; we found that of the rabbit, in which the nerves had been divided, no more distended than the stomach of the other. The food in it had the appearance which it has in a healthy stomach while digestion is going on. The only differ- ences between the contents of the two stomachs were the following. The food which the healthy rabbit had taken during the experiment, was found in the cardiac portion of the stomach, and digestion was going on rapidly in it, while that, which the other had taken at the same time, was still in the oesophagus, and 'conse- quently unchanged. The position this animal had been in was unfavourable to the food's reaching the stomach. There was about a quar- ter of an inch of the" oesophagus, between the food and the stomach, quite empty. The con- tents of the middle portion of the two stomachs could not be distinguished from each other, that in the pyloric end only differed in being of a firmer consistence in the healthy rabbit. In both, the contents of the pyloric end of the stomach were most digested, and in both, the food had equally lost the appearance and smell of parsley, and acquired the smell peculiar to the stomach 1 126 of the rabbit while digestion is going on. The food in the duodenum was equally digested in both. We have seen, that after the eighth pair of nerves are divided, parsley will remain in the stomach of a rabbit wholly unchanged for six and twenty hours. Neither Mr. Hastings nor myself could, from any thing we saw in the sto- mach of the rabbit which was galvanised in this experiment, have doubted its being the stomach of a healthy rabbit. We here see the influence of the brain removed, that of the galvanic trough substituted in its place, and the result the same as if the influence of the brain had still continued. In this rabbit we found the membrane of the trachea of a very deep red colour, but there was not much fluid in it. The lungs did not collapse on opening the thorax, the air-cells being full of a frothy and bloody serum. The lungs were externally of an uniform dark red colour. The heart Avas a little increased in size, and highly vascular. The cause of the great dyspnoea in this experiment, and of the croaking noise, was, that the laryngal nerves were injured by being stretched, in order to divide the eighth pair as near to them as possible, to admit of so large a portion of the former being coated. The reader will see from what is said above, that dyspnoea and a croaking noise are the effects of injuring the laryngal nerves. We learn from the state of the lungs after the division of the eighth pair 127 of nerves, why an animal cannot be long pre- served by artificial respiration after the brain is removed. M. le Gallois, indeed, observes, that artificial respiration produces the same loaded state of the lungs. Throughout the whole of the body there was a general increase of vascularity. This, as appeared from Avhat was observed in other cases, was the effect of the galvanic in- fluence. In these experiments this influence had been directed chiefly to the region of the stomach. In order to see the effect of directing it more particu- larly to the lungs, I requested Mr. Hastings to perform the experiment in the following manner. Exp. 48. A full grown rabbit was kept with- out food for twelve hours. Within two hours of the experiment it was allowed to eat as much parsley as it chose. The hair being then shaved off the skin of the thorax, it was covered with tin foil, but not so low as the pit of the stomach. The eighth pair of nerves were now divided lower down than in the last experiment, and the lower por- tion of both nerves coated with tin foil for about a quarter of an inch. The laryngal nerves were not disturbed, and no croaking ensued. It Avas an hour after the operation before the galvanic influence was so applied as to keep up a gentle twitching of the muscles of the chest and fore- legs. This effect of the galvanism was kept up 128 uniformly for five hours, during which time there was hardly any dyspnoea. In about an hour after this, an uniform effect from the trough could not be kept up on account of the tin foil having been torn. In the course of an hour the breathing became much worse, and we could not again get the tin foil generally ap- plied to the chest. It was kept imperfectly ap- plied till the death of the animal, which happen- ed in about two hours and a half after this ; that is, about nine hours and a half after the divi- sion of the nerves. It seemed to be produced by dyspnoea. The animal had shewn no tendency to vomit. The lungs collapsed on opening the thorax, though not so perfectly as when they are healthy: they swam in water. The inner membrane of the trachea was redder and more vascular than usual. There was no frothy mucus in it. The bronchial cells, near the great division of the trachea, were full of mucus; but on tracing them further, there was very little, and none at all to- wards the surface of the lungs, which was of a deeper red than natural, but not shewing patches of red, as where the eighth pair of nerves are divided without the application of galvanism. The heart was much more vascular than natural. The same observation applies to every part of the thorax. The thoracic viscera, in short, ay ere 129 rather in a state of high inflammation, an effect always produced by a considerable galvanic pow- er in the part to which it was directed, of which the animal evidently died, than in that in which they are found after the division of the eighth pair of nerves. The stomach was larger than natural, and the food but little altered, retaining the colour, smell, and stringiness of the parsley. There was no food in the oesophagus. It is evident that the stomach, in this experiment, was but little ex- posed to the galvanic influence. It was suffici- ently so, however, to prevent the vomiting, and to occasion more change in the food than happens when the nerves are divided without applying galvanism. The reader may remark, that as the stomach is here found in a state intermediate between that of this organ, when the eighth pair of nerves arb di- vided without the application of galvanism, and when the galvanism is chiefly directed to it; so the state of the lungs in Exp. 46 and 47 is in- termediate between what it was in this experi- ment and what it is when the eighth pair of nerves are divided, without the application of this power. As the foregoing experiments were made on a graniverous, a carniverous animal was chosen for the subject of the following experiment, which I requested Mr. Sheppard to perform. I may 130 observe that the three preceding experiments were made in the presence of three, and the fol- lowing experiment in that of four medical men besides myself. Exp. 49. Two small dogs of the same size and age were kept without food for about thir- teen hours; they Were then permitted to eat as much lean raw mutton as they chose. In both, the eighth pair of nerves were divided immedi- ately after they had taken the mutton. In one of them the nerves were coated with tin foil, as they had been in the rabbits, a three shilling piece having been previously bound on the pit of the stomach and lower part of the thorax, after the hair had been shaved off; and galvanism ap- plied as in the foregoing experiments. The dog which was not galvanised was almost immediately affected with dyspnoea, and within ten minutes with violent and repeated efforts to vomit. The other to which the galvanism was applied of sufficient strength to occasion a very gentle motion in the fore-legs, but not any im- pression of pain, breathed as free as before the division of the nerves, and never made any effort to vomit. The application of the galvanism was twice discontinued for a few seconds, during which the animal breathed very laboriously, but on renewing the galvanism the breathing imme- diately became free. This dog lived two hours and a quarter. On opening the stomach after 131 death we found the mutton half digested. It was reduced to a soft pulpy substance, in which there was little or no appearance of muscular fibre. That part of the mutton which lay in the pyloric end of the stomach was most digested, which is always found to be the case in the healthy sto- mach, and affords the best proof that digestion was going on in the usual way. The vessels in some parts of the stomach, and throughout the whole of the small intestines were highly inject- ed, giving those parts a very florid appearance. The lungs were rather redder than natural, but otherwise quite healthy, collapsing perfectly on the thorax being opened. The other dog was still alive at the end of four hours after the nerves had been divided, but so weak that it could not stand nor move itself from the place where it lay on its side. It was killed at this time by a blow on the occiput. The mutton, although it had been in its stomach so much longer than in the other dog, was as firm as when it was swallowed, and perfectly retain- ed both its red colour and fibrous appearance, ex- cept, that on the outside the bits seemed as if they had been dipped in hot water: immediately below the surface they were qnite red. The lungs exhibited the same appearances as thosa of rabbits under the same circumstances. They were so congested that they collapsed very im- 132 perfectly, and their surface was covered with patches of a dark red colour. There was nothing in the stomach of either dog but the mutton, which was taken at the com- mencement of the experiment, and no part of it had been thrown into the oesophagus of either.— All present at this and the three preceding ex- periments examined the state of the stomach and lungs, and expressed their entire satisfaction in the results. Is it possible to explain the results of these experiments without admitting the identity of the nervous influence and galvanism? We must ei- ther admit this, or that there is another power, capable of performing the most characteristic and complicated functions of the nervous system. It is not to be supposed, that we can, By the artificial application of galvanism, direct it in the proper quantity to the proper parts, in such a way as not to supply more to some, and less to others, than nature supplies. Hence, in the fore- going experiments, inflammatory affections and violent action of the muscles were frequently ex- cited by it. This difficulty, which might easily have been foreseen, and the cause of which is so obvious, cannot weaken the inference from the perfect performance of the complicated functions of the nervous system by galvanism. The power of galvanism over the muscles, the 133 phenomena of electric animals, the results of ex- periments which have been laid before the reader, proving that the nervous influence bestows no power on the muscular fibre, but acts only as a stimulus to it, the muscles being thrown into con- traction by the formation of a circle of the nerves and muscles of different limbs, a pile formed of alternate layers of muscle and brain exhibiting galvanic phenomena, and the vast changes which have been effected by galvanism in the hands of able chemists, seem all in some degree to coun- tenance the opinion of the identity of the nervous influence and galvanism. To which I may add, that Sir Everard Home, in a paper published in the Philosophical Transactions for 1809, relates some experiments, from which it appears, that by the power of galvanism albumen may be se- parated from the serum of the blood, both in the solid and liquid form. This subject I shall more than once have occasion to resume. Many cir- cumstances tending to influence our judgment respecting it, remain to be mentioned. 134 SECTION III. Inferences from the preceding Sections. We have seen it ascertained in the first of the preceding sections, that the extreme parts of the sanguiferous and nervous systems are connected in a way very different from that in which these systems are connected in other parts. The heart and vessels of circulation, we have seen, can per- form their functions after the nervous influence is withdrawn. The power of secretion immediately ceases on the interruption of this influence. We must suppose, therefore, either that the nervous influence bestows on the extreme vessels the power of separating and recombining the ele- mentary parts of the blood, or that the vessels only convey the fluids to be operated upon by this influence. It appears from experiments related in the second chapter of the present part of this In- quiry, that the most minute vessels which can be seen by a powerful microscope in the web of a frog's foot, are independent of the nervous sys- tem. The motion of the blood is as rapid, and the circulation in the foot presents precisely the same appearance after, as before the destruction of this system. Is it consistent with these expe- riments to suppose that any part of the sanguifer- 135 ous, derives its power from the nervous system? If the power of the vessels of secretion had been lost by the destruction of the nervous system, would it not have occasioned some change in the distribution and motion of the blood in the web ? The conclusion from these experiments is strengthened by other facts. In those expe- riments in which the power of secretion was destroyed by withdrawing the nervous influence, there appeared to be no defective supply of fluids. Both in the stomach and in the lungs they wjere sufficiently copious. The fault seemed to be, that a due change on them had not been effected. We have no reason to believe, as far as I am capable of judging, that the vessels possess any other than a muscular power, if we except the mere power of elasticity.* Now we have seen * I do not mean here to enter on the arguments which seem to prove that the power of the vessels is, strictly speak- ing, a muscular power. For this subject I refer the reader to the observations of Mr. Hunter. (See his work, intituled a Treatise on the Blood, Inflammation, and Gun-shot Wounds.) * In some animals the muscular structure of the vessels is apparent on the slightest view. In man and animals resembling him it is very obscure, the reason of which Mr. Hunter has pointed out. In them the proportion of the muscular to the elastic coat of the vessels is inversely as the size of the vessels, so that in the larger vessels there is comparatively little muscular fibre, and in the vessels possessing a larger proportion of it, the parts are too minute to enable us to detect it. Theajguments of Mr. Hunter 136 it proved by direct experiment, that the muscular power throughout the whole animal, namely, in the muscles of voluntary motion, the heart and the vessels of circulation, is independent of the nervous system. Can we suppose that the ves- sels of secretion, which are only a continuation of those of circulation, all at once assume a dif- ferent nature? Or, is it at all consistent with our knowledge of the phenomena of chemistry, to conceive that, by any influence, the muscular pow,er can be enabled to separate and recombine the elementary parts of the blood ? The first of the above positions therefore may, I think, be re- garded as set aside. This admitted, does it not seem a necessary inference from the preceding experiments and observations, that in the func- tion of secretion the vessels only convey the fluids to be operated upon by the nervous influ- ence ? If the identity of the nervous influence and galvanism be admitted, we shall find in the known powers of this agent a strong argument in favour of the same opinion. We see galvanism in a thousand instances effecting changes of the are surely much strengthened by the foregoing experiments, which shew that the laws which regulate the power of the vessels of circulation are the same with those which regulate that of the heart, whose muscularity cannot be questioned. The experiments of Burzelius aud Dr. Young afford the strongest argument against the muscularity of vessels by showing that fibrine is not discoverable in their coats. ia7 same kind. In the experiments related by Sir Everard Home, we see it causing a separation of albumen, both in the solid and liquid form, from the se|uj|, where no vessels existed. Thus we have every reason to believe, that the vessels of secretion, like those of circulation, are independent of the nervous system; secretion failing when the influence of this system is with- drawn, not because the vessels of secretion fail to perform their office, but because the necessary changes on the fluids which they supply, no longer take place. We know that the nervous power occasionally influences the vessels of secretion, as Ave have seen it does those of circulation, because affec- tions of the mind frequently occasion an increas- ed flow of fluids to secreting surfaces. The ves- sels of secretion, therefore, obey the same laws as those of circulation. They are independent of, but influenced by, the nervous power. This subject I shall have occasion to resume, in speak- ing of the manner in which the nervous power is supplied to the sanguiferous system. It is not to be overlooked, that the vessels con- vey the fluids to be operated upon by the extreme parts of the nervous system, in a peculiar way. By the lessening capacities of the capillary ves- sels, the blood is divided as by a fine strainer, some of its parts being too gross to enter the small- er vessels. How far the blood may thus be sub-. 20 ^38 divided, we cannot tell. As this structure of the vessels is uniform, Ave have reason to believe that its effect on the blood is necessary to prepare this fluid for the due action of the nervous influence. CHAP. VI. On the principle on which the action of the ali- mentary canal depends; with some observa- tions on an opinion of Mr. Hunter. In order to ascertain how far the peristaltic motion of the intestines is independent of the brain and spinal marrow, the following experi- ments were made. Exp. 50. A rabbit was deprived of sensibility by a blow on the occiput. The whole of the spi- nal marrow was then destroyed by a hot wire. On opening the abdomen we found the peristaltic motion of the stomach, and small and great intes- tines, quite as strong as when the nervous system is entire, as we ascertained by exposing the ab- dominal viscera of other newly-dead rabbits. This motion is as strong in the newly-dead, as in the living animal. Exp. 51. The spinal marrow was wholly re- moved in another rabbit, also deprived of sensi- bility by a blow on the occiput, without at all af- 139 fecting the motion of the stomach and intestines. The removal of the brain, we found, produces as little effect upon it, as that of the spinal marrow. When both were removed at the same time it re- mained unaffected. It continues till the parts be- come cold, so that when the intestines exposed to the air have lost their power, that of those beneath still remains. It appears from these experiments, that the power of the stomach and intestines, like that of the heart and blood vessels, resides in themselves, and is wholly independent of any influence de- rived from the nervous system. Thus we still see that the muscular fibre, in every part in which Ave have examined it, ap- pears to be independent of this system. Mr. Hunter, in a work just referred to, has proved the vitality of the blood, in so clear and convincing a manner, that although the preju- dices of his opponents may still lead them to ob- ject to his arguments, it is impossible to reply to them. This doctrine has been slowly received, because those, who have not been in the habit of correcting by reflection, the ideas received from first impressions, constantly associate their ideas of life with those of sensation and voluntary power. To such, Mr. Hunter's illustration of his opinion by the process of incubation, will be the best reply. We see nothing in the egg on a superficial view but glairy fluids contained in 140 membranes: the blood itself is not more unlike what is usually called life : yet who will doubt the life of an egg, when he sees that if it be mere- ly kept in the proper temperature for three or four weeks, an animal of the most perfect kind, complete in all its parts, comes out of it. Mr. Hunter has shewn, by decisive experi- ments, the analogy which subsists between the contraction of a muscle and the coagulation of the blood. The two acts in many respects obey the same laws. Now the muscular fibre is formed chiefly from that part Of the blood which coagu- lates. The coagulation of the blood every one will allow to be independent of the nervous sys- tem. It takes place at least as readily out of the body as in it, and no nervous filaments pass into the blood. In the formation of this part of the blood into muscular fibre therefore, it must whol- ly change its laws if its poAver now depends on the nervous system ; and we can hardly suppose that the analogies pointed out by Mr. Hunter, could in this case have existed. One of these analogies is intimately connected with the result of some of the preceding experi- ments. It was shewn in the second chapter, that the power of the muscular fibre may be destroy- ed by the most powerful agents acting on the ner- vous system. Mr. Hunter observes, that as the muscles, in instantaneous death from passion, blows on the stomach, or electricity, do not con- 141 tract after death, so the blood under the same cir- cumstances is found not to coagulate. When the latter fact is compared with the experiments just alluded to, it appears a necessary conclusion, that the nervous influence is capable of acting on the blood, a conclusion which must be regarded, I think, as greatly in favour of the identity of this influence and galvanism, for if that conclusion be correct, the nervous influence must be something capable of pervading the fluid as well as the so- lid parts of the body. That electricity and the most poAverful affections of the nervous system produce the same effect, tends also to support this conclusion. The inability of the muscle to contract, and of the blood to coagulate under the foregoing circumstances, Mr. Hunter ascribes to the want of strong action in the muscles and blood where death is so sudden. But it appears from experiments which have been laid before the reader, that strong action, previous to death, tends to destroy the excitability of the muscles, which is always found to remain, as I have as- certained by many experiments, if they have for some time previous to death been at rest, unless it is destroyed by the instantaneous destruction of the nervous power, as in the cases just men- tioned. I have found that even the presence of opium in the system, only exhausts the excitabi- lity of the muscles in proportion to the frequency 142 and force of the contractions it excites in them.* Compare Exp. 19,20, 21, and 22, with Exp. 31. * The convulsions excited by opium always assume the form of the opisthotonos. The animal becomes rigid and is bent backwards. During the intermission of these convul- sions the slightest touch renews them. If the animal is al- lowed to remain undisturbed they but rarely occur. By fre- quently touching it, a constant succession of them may be kept up. In the former case the excitability of the muscles is little impaired, in the latter case it is nearly exhausted. As I have frequent occasion in this Inquiry to mention the effects of opium and tobacco, I shall take the present opportunity of laying before the reader the result of many experiments which I made with a view to ascertain the modus operandi of these drugs on the living animal. It appears from these experiments that their effects may be divided into three classes. 1st. Their effects on any part of the body to which they are immediately applied. In very small quantity they tend to excite muscular action. In larger quantity they imme- diately destroyed the muscular power. They produce these effects in the hollow muscles, the heart, intestines, &c. chiefly when applied to their internal surfaces. When in- jected in considerable quantity under the skin, they destroy the circulation in the part by destroying the power of its vessels. By their operation on the nerves of the part, when applied in small quantity, they produce a degree of excite- ment in the whole nervous system, and, through it, in the sanguiferous system. In large quantity, especially when applied to a very sensible and extensive surface, they pro- duce to a greater or less degree an immediate torpor of the nervous, and, through it, of the sanguiferous system. In all these instances the stimulant effect of the opium is more 143 Of the physiologists, either of our own or for- mer times, none ranks higher than Mr. Hunter. considerable than that of the tobacco, and the sedative effect of the latter is more considerable than that of the former. The second class of the effects of opium and tobacco are those they produce on the sanguiferous system, in conse- quence of their absorption. These effects begin in about a quarter of an hour or twenty minutes after they are re- ceived into the stomach and intestines, and appear to be precisely the same as the effects of opium and tobacco when immediately applied in small quantity to the heart and blood vessels ; but here they are complicated with the third class, into which I would divide the effects of these drugs on the living animal, namely their effects on the brain. These are, some degree of excitement, most remarkable when opium is used, followed, except the quantity be very small, by languor and an inclination to sleep, the former most considerable from tobacco, the latter from opium; and if the quantity be great, by general convulsions of the kind just described when opium has been used, and when to- bacco has been used, by tremblings and paralysis. I have made many experiments to ascertain whether the last effects can arise from the action of opium and tobacco on any other part than the brain, and have found that they never arise from the action of those drugs on any other part. It has been maintained by Dr. Monro and others, that convulsions arise from the action of opium on the nerves of the heart, because they found that on injecting an infusion of opium into the heart, convulsions very quickly ensue. But this only happens in consequence of the infusion passing along the aorta to the brain, for if the aorta be secured by ligature no convulsions take place. The same observations, I have found by experiments frequently repeated, apply to the 144 In originality he has perhaps had no equal: yet I have hitherto had little occasion to mention his name, and in the Report of the National Insti- tute of France, which has been laid before the reader, his name is not mentioned at all. This, which seems at first view to throw some reflec- tion on the importance of Mr. Hunter's labours, is in fact his highest praise. It arises from his having, in his principal physiological investiga- tions, struck into a wholly new field of inquiry; so that in examining the opinions of others, we are hardly led to any mention of his. The same circumstance has occasioned his opinions to be tremblings and paralysis produced by tobacco. Now as these effects of tobacco, and the convulsions produced by opium, always sooner or later ensue to whatever parts of the body they are applied, the experiments above alluded to prove that they are received into the system by means of the absorbents. It would enlarge this note to the-size of a treatise to give a detail of all the experiments from which the above inferences were drawn, for the present therefore I must beg the reader to believe that they were performed with all requisite care. No inference was drawn from any experiment till it had been frequently repeated with the same result. Many of these experiments were detailed in an appendix to the third volume of the second edition of my Treatise on Febrile Diseases. This and another ap- pendix, being a set of experiments made with a view to ascertain the circumstances in diet which influence the spontaneous depositions from the urine, were omitted in the last edition, in order that the work might be comprised in two volumes. 145 but little known abroad. While the attention of physiologists Avas chiefly directed to ascertain the nature of that power on which muscular action depends, and the relation of the muscular and nervous systems, and Avhile in these subjects there were still ample fields of dispute, they were not likely to be diverted from them to in- quiries, apparently unconnected with their fa- vourite objects. Previous to Mr. Hunter, the physiologists of this country joined their endeavours to those of the continent in the above researches. From his childhood he was averse to the restraints of edu- cation, and he at no time bestowed much pains on acquiring a knowledge of the opinions of others. In the volume of nature he found the Avork best suited to his taste. It lay open before him, and uninfluenced by the habits of his prede- cessors, it was not surprising that he should turn to a page different from that on which they had dAvelt so long. Thus he gave a new turn to the pursuits of British physiologists, which has ever since distinguished them from those of the con- tinent. While the latter were occupied in en- deavouring to establish or refute the opinions of Haller, and to add to the valuable facts ascer- tained respecting the subjects of these disputes; the former have in the same way been engaged in endeavouring to support or refute the opinions of Mr. Hunter, and to extend our knowledge of 21 146 the subjects to which he had directed his atten- tion. The advancement of knowledge will necessa- rily draAV together these different sects of physio- logists, and the objects of their pursuit will at length become the same. As they acquire a more perfect knowledge of the animal oeconomy, each sect will perceive that the discoveries of the other are necessary for the advancement of their own, and the endeavours of all will thus be directed to one end. Mr. Hunter's name, we may venture to predict, will then stand as high in other coun- tries as it does in his own. I do not mean to say with the blind admirers of Mr. Hunter, that we know nothing but what he has taught us, and that foreign physiologists might have learnt from Mr. Hunter what they have learned from their own labours. He has not laboured in the same field with them, he has broken new ground, in the cultivation of which they will join: he has opened new views, for which they will make their acknowledgements, as soon as the determi- nation of the questions, by Avhich they have been so long occupied, gives them leisure to view what he has done in another and not less important part of the same subject.* * I say nothing here of the great pathological labours of this acute observer. There are two peculiarities of Mr. Hunter's writings, which will tend to prevent their becoming popular with foreigners; an occasional obscurity of style, 147 We are iioav to inquire whether the alimenta- ry canal, like the heart and blood vessels/is ca- pable of being stimulated through the nervous system. CHAP. VII. On the relation which the alimentary canal bears to the nervous system. The alimentary canal is of such importance in the animal oeconomy, that it is of the first conse- quence in tracing the laws of the vital functions to ascertain the principle on which its action de- pends, and the relation which subsists between it and the nervous system; the former of these points I have endeavoured to ascertain by the ex- periments related in the preceding chapter, the latter we are now to consider. and a degree of refinement which often loses sight of all cor- rect rules of reasoning; an example of the latter we have in his doctrine of the stimulus of necessity. The reader will not be surprised to find in the works of Mr. Hunter, repetitions and other marks of their often hav- ing been composed in haste, and under the pressure of many engagements. These, while they lessen the accuracy of the works, tend perhaps rather to raise our opinion of their au- thor, for he is never betrayed into a neglect of the great lines of his subject, or inaccuracies of consequence. 148 Exp. 52. I endeavoured to ascertain how far the motion of this canal is influenced by stimuli applied to the brain and spinal marroAV; but from its nature it is in every way so irregular that no certain result could be obtained. It often appear- ed that spirit of wine applied to the brain and spinal marrow increased it. The admission of air into the cavity of the ab- domen throws the bowels into strong spasmodic action, which alone would obscure any effect that can be supposed to arise from stimulating the brain. The abdomen was therefore opened un- der tepid water, but this was found to excite even stronger spasms than the air had done. The ef- fects of the passions on the alimentary canal, how- ever, leave no room to doubt that it is capable of being stimulated through the nervous system. It remains to be ascertained whether it is subject only to certain parts of the brain, or, like the heart, to every part of that organ and of the spi- nal marrow. It is evident, from the circumstances just men- tioned, that it is impossible to answer this ques- tion respecting the alimentary canal, as respect- ing the heart, by agents applied to different parts of the brain and spinal marrow. Before I relate the experiments which I had recourse to for this purpose, I shall make some observations on the process of digestion in the animal on which these experiments were made, which will place in a 149 clearer point of view both their results, and those of some experiments which have been laid before the reader. SECT. I. On the process of Digestion. On the functions of the stomach all other func- tions of the animal body may be said to depend, as their various organs derive from it that supply, without which they can exist only for a very short time. In another point of view we find the sto- mach equally important. There is no other or- gan whose diseases are at once so frequent and so varied, or which partakes more, perhaps so much, of the diseases of other parts, or of the whole system. It is not however my intention to enter fully into that part of the process of digestion which is performed in the stomach. The experiments of Spalanzani and others sufficiently prove that the change which the food undergoes in this organ is effected by a fluid secreted by it. I shall con- fine myself to such circumstances attending this change as serve to elucidate the results of the ex- periments which have been or are about to be laid before the reader. I have inspected after death, under various 150 circumstances, and at different periods after tak- ing food, the stomachs of about a hundred and thirty rabbits, which has enabled me not only to ascertain some points that will place the result of many of my experiments in a clearer light, but to observe more particularly than has been done by others, the process of digestion in this animal: which, from the ease with which it can be pro- cured, and its tenacity of life, has been so much employed in physiological investigations. How far the following observations will apply to other animals I cannot say. In carniverous animals the process of digestion may be different, and in animals furnished with a gizzard, in some respects, it certainly is so. A knowledge of this process in any one animal, however, must be useful in our attempts to trace it in others. The experiments on this part of the subject were so frequently repeated, that it would be te- dious and unprofitable to give an account of each experiment. I shall here therefore, under the head experiment, give the result of all the expe- riments on each particular part of the subject. Mr. Sheppard was so good as to assist me in these experiments. Exp. 53. The first thing which strikes the eye on inspecting the stomachs of rabbits which have lately eaten, is, that the new is never mixed with the old food. The former is always found in the centre, surrounded on all sides by the old food, 151 except that on the upper part, between the new food and the smaller curvature of the stomach, there is sometimes little or no old food. If, as we ascertained by more than twenty trials, the old and the new food are of different kinds, and the animal is killed after taking the latter, unless a great length of time has elapsed after taking it, the line of separation is perfectly evident, so that all the old may be removed Avithout disturbing the new food. For this purpose we fed rabbits on oats, and after making them fast for sixteen or seventeen hours, allowed them to eat as much cabbage as they chose, and killed them at differ- ent periods, from one to eight hours after they had eaten it. On opening the stomachs of rabbits three or four weeks old, Avho both sucked and eat green food, we always found the curdled milk unmixed with the green food. Before the stomach was opened we could, from its transparency, see where the green food and where the milk lay. The rabbits used in this and all the experiments which I am about to relate in this section, were killed by a blow on the occiput. Exp. 54. If the old and the new food be of the same kind, and the animal is allowed to live for a considerable time after taking the latter, the gastric juice, passing from the old to the new food, and changing as it pervades it, renders the line of separation indistinct; but towards the 152 small curvature of the stomach, and still more to- wards the centre of the new food, we find it, un- less it has been very long in the stomach, com- paratively fresh and undisturbed. All around, the nearer the food lies to the surface of the sto- mach, the more it is digested. This is true even with regard to the small curvature compared with the food near the centre, and the food which touches the surface of the stomach is always more digested than any other found in the same part of the stomach. But unless the animal has not eat- en for a great length of time, it is in very differ- ent stages of digestion in different parts of the stomach. It is least digested in the small curva- ture, more in the large end, and still more in the middle of the great curvature. These observations apply to the cardiac por- tion of the stomach. Sir Everard Home, in his work on Comparative Anatomy, has shewn that the stomach is divided into two portions, the car- diac and pyloric, in such a way, that the length of the former is to that of the latter nearly as two to one. The line of division may generally be seen in some animals after death. He says it is more evident while digestion is going on. I have sometimes observed it very distinctly after death in the stomach of the rabbit, and have then found the food in the two cavities divided by an evident line of separation as described by this author. These two portions of the stomach form an an 153 gle with each other, Avhich is well expressed by the plates in Sir Everard Home's Avork. Exp. 55. The food in the pyloric portion of the stomach of the rabbit, is ahvays found in a state very different from that just described. It is more equally digested, the central parts dif- fering less in this respect from those Avhich lie next the surface of the stomach; it is evident, however, that all the change effected in the sto- mach is not completed when the food enters this portion of it, because we find it the more digested the nearer it approaches to the pylorus, where being ready to pass into the intestine, it has un- dergone all that part of digestion which, is per- formed in the stomach. One of the most remarkable differences be- tween the state of the food in the cardiac and pyloric portions of the stomach, is, that in the latter it is comparatively compact and dry, in the former mixt with a large proportion of fluid, par- ticularly when digestion is pretty far advanced, and time consequently has been given for a con- siderable secretion from the stomach. In the rabbit indeed, which is fed only with solid food, in the early stage of digestion it is nearly as free from liquid in the cardiac as in the pyloric por- tion of the stomach. When digestion is very far advanced, the whole contents of the former are often reduced to the state of a semi-fluid. But even then the food in the pyloric portion, par- 22 154 ticularly those parts of it which are near the pylorus, are comparatively compact and dry. In rabbits so young as to live wholly on milk, the curdled milk is considerably softer and moister in the cardiac than in the pyloric end of the sto- mach. An interesting question here arises, what becomes of the liquid part of the contents of the cardiac portion of the stomach when the solid part is moved on towards the pylorus ? This question has particularly engaged the attention of Sir Everard Home. What first suggests itself is, that, as the stomach is con- stantly secreting a fresh supply of fluids, for the purpose, of digestion, those which have performed their office, and are no longer useful in this ca- vity, are removed by absorption, analogous to what appears to be constantly going on in other parts of the body. But Sir Everard Home re- lates several experiments, from which he infers that liquids are removed from the cardiac por- tion of the stomach by some other means than the absorbent system. What these means are, he found it impossible with certainty to determine. Exp. 56. Although the food is in the most di- gested state in the pyloric end, it appears from several circumstances that the change is chiefly effected in the great end of the stomach. The food found in the pyloric end we have just seen is comparatively dry, while that found in the great end, if digestion is much advanced, is mix- 155 ed copiously with the juices of the stomach, and there is a more, evident difference in the state of the food before it comes into this part, and when it is about to leave it, than in any other part of the stomach. I shall presently have oc- casion to mention a fact ascertained by Mr. Hun- ter, which seems to confirm this opinion. Mr. Hastings on examining the stomach of a woman who had died under his care, found it every where in a state of ulceration, except in the great end, Avhere it was healthy. The stomach had performed its functions to the last, and the fasces proved that the food had been properly digested. It appears that in proportion as the food is digested, it is moved along the great curvature, Avhere the change in it is rendered more perfect, to the pyloric portion. Thus, the layer of food lying next the surface of the stomach is first di- gested. In proportion as this undergoes the pro- per change, it is moved on by the muscular ac- tion of the stomach, and that next in turn suc- ceeds to undergo the same change. As the gas- tric juice pervades the contents of the stomach, though apparently in no other way than by sim- ple juxtaposition, for the arrangement of the food above described, we never found disturbed, the change in each part, which in its turn comes in contact with the stomach, is far advanced be- fore it is in actual contact with it; and conse- quently is soon after this in a proper state to be 156 moved on towards the pyloric end. Thus a con- tinual motion is going on, that part of the food which lies next the surface of the stomach pass- ing toAvards the pylorus, and the more central parts approaching the surface. Whether food is ever so digested in the small curvature, as to be sent to the pyloric portion, without having tra- versed the large curvature, I have not been able to ascertain. When rabbits have fasted six- teen or eighteen hours, the whole food found in the cardiac portion, which is in small quantity compared to what is found in it immediately af- ter a full meal, seems frequently to be all nearly in the same state with that next its surface, the gastric juice having pervaded and acted upon the whole, and is consequently apparently fitted to be sent to the pyloric end. Sir Everard Home found that the stomach of a rabbit never empties itself, containing even when the animal dies after long fasting, a considerable quantity of food.— The first impression on the food is made in the small curvature, because the upper part of the new food, which lies contiguous with this part of the stomach, or nearly so, is always found more changed than the more central parts of it. We frequently found in the large end of the stomach the small round masses or balls, about the size of the largest kind of shot, mentioned by Sir Everard Home. These balls are very constantly found in the great end of the stomach 157 of rabbits, especially when fed on green food, never in any other part of it. They are often very numerous, sometimes forming the whole contents of that part of the stomach. They cannot be fewer in many cases than from tAVo to four hundred. At other times they are much less numerous, and mixed with food of the same con- sistence Avith that of which they are formed. It is difficult at first view to account for their ap- pearance. The ingenious idea of Sir Everard Home that they are produced by the rabbit occa- sionally ruminating, is opposed by several cir- cumstances ; the frequency of their appearance, their sometimes forming one half or more of the contents of the stomach, their being always found at a considerable distance from the opening of the oesophagus into the stomach unless their number is so great as to fill the greater part of the sto- mach, food much less digested than that compos- ing them generally lying betAveen them and this orifice, and no appearance of this kind being found in ruminating animals. It was long before I could form even a proba- ble conjecture respecting the formation of these balls. I have now, from inspecting many sto- machs containing them, very little doubt of the cause to Avhich they are to be ascribed. When the stomach of the rabbit is laid open, the great end is found corrugated forming rugae, which give it a honey-comb appearance. These rugae 158 disappear when it is stretched, and as soon as the stretching poAver is withdrawn, again appear, the rest of the stomach being comparatively smooth. The balls seem to be formed in the hollows of these rugae, which are about the same size with the balls. It would appear that the food by the action of this part of the stomach, is rolled up into these masses after it has undergone that part of the digestive process which takes place in the great end of the stomach, and conse quently after it has been exposed for a conside- rable time to the action of the gastric juice; in which form it is sent towards the pyloric end, Avhere the balls are broken down, and the whole again formed into one mass of a firmer consist- ence than the balls. I have observed that when all the food in the great end of the stomach is com- posed of these balls, it contains no fluid but that Avhich is mixed up with the food in them. Some- times no balls are formed. This is comparatively rare. We never found the curdled milk formed into balls, consequently there are no balls in the stomachs of very young rabbits. With this exception they are frequently, I may say very generally, found under all circumstances of diet, situation, &c. Sometimes when rabbits had lived precisely in the same way, they were not found in all. They are sometimes found, when the more central parts of the contents of the stomach have undergone little or no change. 159 Exp. 57. It is in the great end of the stomach where digestion appears to go on so rapidly, that Mr. Hunter found the stomach itself dis- solved; and by the most satisfactory arguments shewed that this is the effect of the gastric juice after death. His observations on this subject confirm the foregoing view of digestion, for he found part of the stomach digested when the food it contained remained undigested, in the case of a man killed immediately after a full meal. This I have often observed in rabbits, when the animal has been killed immediately after eati«g, and allowed to lie undisturbed for some time. On opening the abdomen we have found the great end of the stomach soft, eaten through, sometimes wholly consumed, the food being only covered by the peritoneum, or lying quite bare for the space of an inch and a half in diameter, and part of the contiguous intestines, in the last case, also consumed; while the cabbage, which the animal had taken, lay in the centre of the stomach unchanged, if we except the alteration which had taken place in the external parts of the mass it had formed, in consequence of im- bibing gastric juice from the half digested food in contact with it. We sometimes found the great end of the stomach digested within an hour and a half after death; it was more frequently found so when the animal had lain dead for many hours. The great end of the stomach is 160 not always dissolved, however long the animal has lain dead. This seems only to take place when there happens to be a greater supply than usual of gastric juice. Thus Ave always observed it most apt to happen when the animal had eaten voraciously. Why it should happen without the food being digested is evident, from what has been said. Soon after death, the motion of the stomach, which is constantly carrying on towards the pylorus the most digested food, ceases. Thus the food, which lies next the surface of the sto- mach, being fully saturated with gastric juice, neutralises no more; and no new food being pre- sented to it, it necessarily acts on the stomach itself, now deprived of life, and on this account, as Mr. Hunter justly observes, equally subject to its action with other dead animal matter. It is remarkable that the gastric juice of the rabbit, which in its natural state refuses animal food, should so completely digest its OAvn stomach, as not to leave a trace of the parts acted on. I never saw the stomach eaten through except in the large end. In other parts its internal mem- brane is sometimes injured. Keeping in view the foregoing account of the process of digestion in the rabbit, it will be inte- resting to trace the effect produced on it by de- priving the stomach of a great part of its nervous influence, which is done by dividing the eighth pair of nerves. 161 The division of the eighth pair of nerves, which I have had such frequent occasion to mention, is one of the oldest physiological ex- periments of which we have any account. It was performed by several of the ancients, and has been repeated by a great many physiologists in modern times. Valsalva is among the first who gave any distinct account of its effects on the stomach. He observes that it impedes di- gestion, and even prevents the food passing from the oesophagus into the stomach. The cause of part of the food being found in the oesophagus I have had occasion to point out above. Haller frequently repeated this experiment, and ob- serves that the powers of digestion were always suspended by it. Since his time it has often been made by others with the same result.* * It is said that M. Maguedie has divided the eighth pair of nerves immediately above the diaphragm, and found that the stomach is still capable of performing its functions. Of the effects of the division of the eighth pair of nerves at this place I cannot speak, as I have never seen the experiment made. Its effects on the stomach, it is evident, may be dif- ferent from that of the division of these nerves in the neck, because they form various connections with the great sym- pathetic nerve in the thorax. By dividing the eighth pair of nerves in the neck, the stomach is deprived of the whole, or nearly the whole, power of these nerves. It seems sur- prising that a warm-blooded animal should live long enough to afford proof of the functions of the stomach being per- fectly performed, after so severe and tedious an operation, in the cavity of the thorax. 23 162 I was greatly puzzled at first by observing, that if the animal be allowed to live for a consi- derable time after the division of these nerves, the food remaining in the stomach is always found undigested, and nearly in the same state in all parts of the stomach. This effect Avas uniform; I never saw it otherAvise. Yet we must conceive that at the time the animal last eats, there is some food more or less digested in its stomach, and some gastric juice to act on part of that just received into it. The foregoing statements explain the difficulty. The division of the eighth pair of nerves destroys the secre- tion of the gastric juice, but the animal still living, and the motions of the alimentary canal being independent of the nervous influence,* the usual motions of the stomach continue, and send onwards into the intestines all the food which is digested, and consequently can apply to the sto- mach that stimulus which excites its natural motions. Thus it is evident from the foregoing observations, that the undigested food must at length come into contact with it. As soon as this happens, the usual secretions not being sup- plied to produce the proper change in it, an unnatural motion is excited; hence the efforts to vomit, which always ensue in about an hour, an hour and a half, or two hours after the division * See Chap. VI. 163 of the nerves, marking the time when the sto- mach, having sent towards the pylorus its di- gested contents, begins to feel the effects of undigested food coming into contact with it. If the animal be allowed to eat after the opera- tion, the vomiting almost immediately ensues; the food, as appears from the above statement, and, indeed, as is evident from the way in which it enters the stomach, almost immediately coming in contact with some part of the small curvature, and there not meeting with the secretions, which, as explained above, make the first-impression on it. Thus we see the cause of the efforts to vomit, which ensue on the division of the eighth pair of nerves; and why, if the animal be allowed to live for a certain time after the operation, nothing but undigested food is found in the stomach. SECT. II. On the effects on the stomach and lungs of de- stroying certain portions of the spinal marrow, compared with those of dividing one or both of the eighth pair of nerves. From the extreme irregularity of the motions of the alimentary canal, I have already had occa- sion to observe, we cannot ascertain whether it is subject to the influence of the different parts of 164 the brain and spinal marrow in the way in which this has been done respecting the heart. I there- fore endeavoured to ascertain this point by Avith- drawing from the most important part of this canal, the stomach, the influence of different parts of these organs, and observing the effects produced on it. As we have seen the office of the stomach de- stroyed by the division of the eighth pair of nerves, we should at first view infer, that it is from the brain alone that the stomach derives its nervous influence. But although the process of digestion is suspended by the division of these nerves, it does not follow that the stomach may not derive nervous influence from other sources, because the loss of any considerable part of its nervous energy may destroy its function. Be- sides, its remaining sensibility, indicated by the efforts to vomit, proves that its nervous influence is not wholly withdrawn by dividing the eighth pair of nerves. If, then, the nervous influence be not supplied to the stomach by the eighth pair of nerves alone, but also, as we have reason to believe from the evidence of anatomy, by nerves arising from dif- ferent parts of the spinal marrow, it is evident, that cutting off its supply from any considerable part of this organ, while we leave the eighth pair en- tire, must affect its power, though probably not so much, because the brain, we have reason to believe, constitutes the largest and most impor- 165 tant part of the nervous system. To ascertain this point the following experiments were made. Exp. 58. A hole was made about the middle of the spine, and the loAver part of the spinal mar- row destroyed by a small wire. The only ap- parent effect of the operation was the total paraly- sis of the lower part of the animal., It seemed to be otherwise in health. It was allowed to eat nothing for twelve or fourteen hours. At the end of this time it ate parsley very readily, and in large quantity, without any tendency to vomit. It lived twenty-four hours after the operation, and ate parsley from time to time. On opening the abdomen after death, the sto- mach was found distended to a great degree, ap- parently containing the whole of the parsley which had been eaten after the operation, in an undigested state. It had passed no urine after the operation, and the bladder was so much dis- tended, that it rose above the umbilicus. Some faeces had passed. The lungs collapsed on open- ing the thorax, but were slightly congested. Exp. 59. In a full-grown rabbit a small Avire was introduced into the spine at the fourth lum- bar vertebra, by which we endeavoured to de- stroy the spinal marrow as far as the first dorsal vertebra. The hind legs were rendered insensi- ble and motionless. Respiration was a little dis- ordered. In a short time after the Operation the animal appeared lively and ate some parsley. 166 The respiration continued to be slightly affected. Some hours after the operation Mr. Hastings watched the animal, observed it to be very cold, and it shivered, although it was kept in the same temperature with other rabbits, who shewed no signs of being cold. The rabbit used in the last experiment also seemed cold, but not in the same degree. The respiration now seemed much dis- ordered, and the animal refused parsley. It was then brought near a fire and wrapped up in flan- nel. By these means it was soon relieved, the shivering ceased, its eyes looked more lively, and the breathing became more free. It was kept near the fire as long as it lived, and frequently ate parsley. It died in twenty-seven hours after the operation. The abdomen was found full of urine, the bladder having been ruptured. The peritonaeum was inflamed, and the rectum much distended with faeces. The stomach was not much dis- tended. The parsley near the cardiac orifice Avas not at all changed, and that near the pyloric orifice very slightly. The membrane of the tra- chea and bronchia was more vascular than natu- ral. The bronchial cells were slightly loaded with frothy and bloody mucus, and there were the same red patches in the lungs as after divid- ing the eighth pair of nerves. On examining the spinal marrow as far as the wire had passed we found blood extravasated in 167 different parts, and its membranes were much in- flamed. Immediately above the opening the spi- nal marrow was quite destroyed for about an inch in length. In other places it did not appear much injured. Exp. 60. I wished to ascertain the effect of destroying a smaller portion of the spinal marrow than that destroyed in either of the last experi- ments, and requested Mr. Hastings to perform the following experiment, noting the temperature of the animal at the different periods of it. In a rabbit about two months old, fed on parsley, a small wire was introduced into the spinal canal, at the first lumbar vertebra, and that part of the spinal marrow which lies beloAV this vertebra, de- stroyed. After mentioning the other circumstan- ces of the experiment, I shall throw together the observations made on the temperature. The ani- mal lost the power of the lower extremities, but seemed in no other Avay immediately affected by the destruction of this part of the spinal marrow. It lived thirty-five hours. On examining it after death, the stomach was found no larger than natural, the parsley retained its colour, smell and fibrous texture, although such a change had taken place in it, as demon- strated a very slight degree of the digestive pro- cess. The duodenum for about an inch beloAvr the pylorus was filled Avith parsley in the same 168 state. The bladder and rectum were distended, but not so much as in the two last experiments. The lungs were slightly congested. It is difficult to destroy a large portion of the spinal marrow without immediately killing the animal. It must be done very slowly, and even with this precaution the attempt will not always succeed. On examining the lumbar portion oi* the spinal marrow, after death, it was found com- pletely destroyed. . The following are the observations on the tem- perature. The bulb of Farenheit's thermometer intro- duced into the mouth, and kept there for two mi- nutes previous to the experiment, stood at 98°. The animal was kept in a warmer temperature after, than before the destruction of the lumbar portion of the spinal marrow. The temperature was always measured by putting the bulb of the thermometer into the mouth, and keeping it there for two minutes. Immediately after the operation, therm. 98° In twelve minutes after it 92° In half an hour after it - - - 92° In two hours and a half after it - - 98° In five hours and three-quarters after it - 98° In seven hours and a quarter after it - 98° In nine hours after it - - - - 96° In ten hours after it - 95c 169 The animal during all this time appeared live- ly and eat parsley. In eleven hours after it, therm. - - S6° In twelve hours after it - - - - 97° Night coming on, the temperature was not mea- sured again for thirteen hours. In the morning the rabbit appeared lively and eat readily. In twenty-five hours after the operation, therm......- 88° In twenty-seven hours after it, therm. - 84° In twenty-nine hours after it - - 88° In thirty hours after it - - - - 84° In thirty-one hours after it - - - 84s In thirty-three hours after it - - - 80° The animal still continued to eat. In thirty- four hours after the operation the temperature was 75°. In an hour after this, the animal died. This animal did not appear nearly so cold as that in the preceding experiment, in which a larger and more important part of the spinal marrow was destroyed. Thus we find the function of the stomach im- peded by depriving it of the influence of any con- siderable part of the spinal marrow, and it seems only more affected by the division of the eighth pair of nerves, in proportion to the greater extent and importance of the brain. It is remarkable, that the result of the first of these experiments is the same with that which M. le Grallois obtained when he had divided one of 24 170 the eighth pair of nerves in a Guinea pig. The animal did not vomit, and the stomach was found distended to a great size, apparently containing all the food it had taken after the operation, in an undigested state. This coincidence demonstrates how much the same the effect on the stomach is, whether we deprive it of part of the nervous in- fluence, which it receives from the brain, or part of that which it receives from the spinal marrow. Mr. Hastings, at my request, made this experi- ment on a rabbit. Exp. 61. One of the eighth pair of nerves was divided in a rabbit. No difficulty of breathing immediately ensued. The rabbit continued to eat from time to time, with occasional attempts to vomit, and once it brought up a little of the pars- ley. It laboured under a slight degree of dysp- noea. A short time before its death, which hap- pened in twenty-four hours and a half after the division of the nerves, the dyspnoea suddenly in- creased with restlessness. On examining the stomach after death, we did not find it much distended. The food was very little changed. The oesophagus did not contain much food in the upper, in the lower part it was much distended with it. The bronchia were much less loaded than when both nerves had been divided. The larynx was found quite full of the parsley, in consequence of the epiglottis's having, by some strange accident, been caught in 171 the membrane of the pharynx, so as to prevent its falling down on the glottis. In consequence of this accident, which was evidently the cause of death, the experiment was repeated. Exp. 62. One of the eighth pair of nerves was divided in a rabbit. It eat soon after the opera- tion, but did not vomit till two hours and a half after it, and then dyspnoea came on. The breath- ing at times was almost free, and the vomiting only occurred at intervals. Both subsided when it was prevented eating. It died forty-five hours after the operation. The stomach was found after death larger than natural, being distended with flatus, and con- taining more food than usual. For the most part the parsley was in the same state as Avhen taken into the stomach, both in appearance and smell. In some places it was slightly changed. There was undigested parsley in the duodenum, to the distance of about an inch from the stomach. The lower end of the oesophagus contained a little pars- ley. There was none in any other part of it. When we compare this experiment with the experiments in which galvanism was used, the difference of result is very striking. Here, al- though only one nerve was divided, parsley had remained in the stomach and duodenum unchang- ed for nearly two days. There, although both nerves were divided, the whole food contained in the stomach, although it had lain in it a compara- 172 tively short time, was found nearly as much changed as in the stomach of a healthy rabbit. The membrane of the trachea was of a darker colour than natural, its vessels being distend- ed with blood, and there was some frothy mucus in it. The lungs were slightly congested. The membrane of the bronchia was too vascular, and the air-cells contained some frothy mucus. All these appearances existed in a much less degree than when both nerves were divided. The lungs collapsed imperfectly on opening the chest.— There were some dark coloured spots on them. If the reader will take the trouble to compare these appearances with those observed when part of the spinal marrow was destroyed, particularly in Experiment 59, he will see that the division of one of the eighth pair of nerves produces near- ly the same effect on the lungs and stomach, as the destruction of part of the spinal marrow. I wished to see the effect on the stomach and lungs of destroying nearly the whole spinal mar- row. But with all the precautions that could be taken the animal died almost immediately. It is difficult indeed to prevent immediate death, when as much of it is destroyed as in Experiments 58 and 59. There is still another point in this part of the subject, which remains to be ascertained. Do the effects observed on the stomach and lungs, when part of the spinal marrow is destroyed, 173 arise from the destruction of that part; that is; from the ceasing of its office, or from the influence of the brain on the spinal marrow being thus li- mited? It is evident, that if the former opinion be correct, the division of the spinal marrow in the middle, will not produce the same effects as the destruction of the lower half. If the other opi- nion be correct, these must produce precisely the same effects. Exp. 63. The spine was divided in an old rabbit, about the same place at which it was opened in order to destroy the lower half of the spinal marrow in Experiment 58, after which there was no motion in the lower extremities.— The rabbit seemed lively after the operation, and continued to eat frequently till within six hours of its death. It died in twenty-seven hours and a half after the division of the spinal marrow.— It had not vomited, and had had little or no dyspnoea. On examining the stomach after death, it was not found more distended than natural. The food it contained, was nearly as well digested as in the stomach of a healthy rabbit. The con- tents of the duodenum had completely undergone the proper change. The bladder and rectum were distended, but not so much as after the de- struction of the lower part of the spinal marrow. The lungs collapsed on opening the thorax, but contained a little frothy mucus. 174 On examining the spine it was found to have been completely divided. On comparing this experiment with Experi- ment 58, we see that here the lower part of the spinal marrow still performed its office, and sup- plied its portion of nervous influence to. the gang- lia, although the communication between it and the brain was cut off. The reader must have perceived through the whole of these experi- ments, that any considerable diminution of the nervous influence, almost wholly deprives the sto- mach of its power; and even the slightest dimi- nution of it seems to be felt. I have no doubt, that we may ascribe the, very slight derange- ments observed in the stomach and lungs in the last experiment, to the destruction of function, that must have taken place in the part of the spi- nal marrow at which it was divided. The bruise occasioned by the wound must of course have de- stroyed the function of a small part on each side. Thus we find that although we cannot by agents applied to different parts of the brain and spinal marroAV, ascertain how far the stomach and lungs are under their influence, we may, by withdraw- ing the influence of different parts of the former organs, prove that the stomach and lungs, like the heart, are capable of being influenced through every part of them. 175 CHAP. VIII. On tlie cause of Animal Temperature. We are now to attend to the temperature of the animals in those experiments, in which por- tions of the spinal marrow were destroyed. It appears from them that while the destruction of part of the spinal marrow impedes the office of secreting surfaces, it also lessens the evolution of caloric. Mr. Brodie, in the Croonian Lecture for 1810, gave an account of experiments which led to the inference, that the production of ani- mal temperature is under the influence of the ner- vous system: and in the Philosophical Transac- tions of 1812, he relates additional experiments, tending to strengthen this inference. In the se- cond Section of the last Chapter, I have had oc- casion to relate experiments made for other pur- poses, which tend in a striking manner to confirm the opinion of Mr. Brodie. He found that poi- sons impairing the vigour of the nervous system impair the temperature. In the foregoing expe- riments lessening the extent of this system by de- stroying part of the spinal marrow had the same effect. Towards the conclusion of the latter of the above papers, Mr. Brodie observes, " The facts here, as Well as those formerly adduced, go far 176 towards proving, that the temperature of warm blooded animals is considerably under the in- fluence of the nervous system; but what is the nature of the connection between them? Whether is the brain directly or indirectly necessary to the production of heat ? These are questions to which no answers can be given, except such as are purely hypothetical. At present we must be content with the knowledge of the insulated fact: future observations may perhaps enable us to refer it to some more general principle." The various phenomena of animal tempera- ture, and the experiments on this subject, related in the last chapter, compared with those on se- creting surfaces, seem to me to prove, that the caloric, which supports animal temperature, is evolved by the same means, namely, the action of the nervous influence on the blood, by which the formation of the secreted fluids is effected, and consequently that it is to be regarded as a secretion. If this view of the subject be correct, and galvanism be capable of performing the functions of the nervous influence, it ought to occasion an evolution of caloric, as it effects the formation of secreted fluids, from arterial blood, after the nervous influence is withdrawn. To ascertain this point, the following experiments were made. Exp. 64. A cup was placed in water of the temperature of 99° of Farenheit's thermometer, 177 which was ascertained to be the temperature of the rabbit, on whose blood the experiment was made, by placing tiie bulb of the thermometer in the rabbit's mouth, and allowing it to remain there for two minutes. The temperature of all the rabbits used in the following experiments Was ascertained in the same way. Blood was received into the cup from one of the carotid ar- teries. The bulb of a small thermometer, raised to 98°, and the wires from the different ends of the galvanic trough, abovementioned, the whole trough being charged, were immersed into it. The blood had been in the cup about two mi- nutes before the whole apparatus was arranged. The same quantity of blood, taken from the same vessel of another rabbit of the same age and tem- perature, was received into a cup, also placed in water of the temperature of 98°. So far, how- ever, from perceiving any evolution of caloric from the effects of the galvanism, the blood in the galvanised cup seemed to cool rather faster than that in the other. The appearance of the blood in the two cups, however, was very dif- ferent : that, in which the wires were immersed, assumed a dark venous colour, and most of the coagulum, which had appeared to form more ra- pidly in this than the other blood, was soon dis- solved, the blood again becoming liquid. The blood in the other cup retained the florid colour, and coagulated as usual. 25 178 It occurred to me, that the galvanism in this experiment had perhaps been applied too late to produce all its effect on the blood. For we must suppose the changes of this fluid to commence as soon as it leaves the vessels : with the assistance of Mr. Hastings, and another gentleman, there- fore, I repeated the experiment in the following manner. Exp. 65. The rabbits were chosen of the same size and temperature, the thermometer in the mouth of each standing at 98°. The cups were disposed as in the last experiment; the water, in which they stood, being at the temperature of 98°. Into the one cup nothing was put but the thermometer; into the other, the thermometer and the two wires from the different ends of the galvanic trough, one on each side of the bulb; the thermometer, raised to 98°, being put into the cups at the moment the blood began to flow. Assistants held the rabbits Avhile Mr. Hastings divided the carotid arteries previously exposed. I observed the thermometer, and a person hav- ing a watch marking seconds, noted doAvn the changes of the thermometer as I mentioned them, and the times at which they took place. The experiment aa as made first on the blood of the one rabbit, and then on that of the other; but to save repetition, I relate it as if it had been made on both at the same time. . The tempe- rature of the mouth is ahvays the temperature 179 of the blood on its first flowing from the ves- sel. In the cup, where there Avas only the ther- mometer, one minute after the blood began to flow into it, the thermometer stood at 97°? in a quarter of a minute more it stood at 96°, and so on gra- dually falling; for it is to be observed, that al- though the cups stood in Avater of 98°, the air in them was more than ten degrees lower. In the cup, where the wires were, one minute after the blood had begun to flow into it, the ther- mometer stood at 100°, in half a minute more at 102°, in half a minute more at 100°, in a minute more at 99°, in half a minute more at 98°, that is in three minutes and a half after the blood had begun to flow into the cup. After this, the ther- mometer gradually fell. While the above changes of temperature went on, the blood in the galvanised cup began to assume a dark colour about the positive wire. But it appears from the preceding experiment, that the evolution of caloric was not connected with this change of colour, which took place as quickly where no caloric was disengaged. Be- sides the caloric ceased to be evolved soon after the dark colour appeared about this wire, and by keeping up the supply of galvanism, the dark co- lour continued to extend after the evolution of caloric had ceased, till the whole blood in the cup assumed this colour. Air bubbles arose around both wires. Around the negative wire 180 they continued to rise in such quantity as to form a considerable accumulation of froth. All these appearances took place equally, whether the wires were immersed in the blood at the moment it flowed from the vessel, or after the time had elapsed, at which they occasioned an evolution of caloric. Exp. 66. That I might be assured that we were not deceived in the first experiment, we al- lowed blood to flow from the carotid artery of a rabbit into a cup placed as above, and after it had remained in the cup only about a minute and a half, during Avhich no change of appearance took place in it, the Avires and thermometer were im- mersed into it. The change of colour, and other phenomena mentioned above, took place exactly as before ; but there was no evolution of caloric, the blood continued gradually to cool. Exp. 67. In a rabbit, whose temperature was only 96°, both carotids were exposed. It was then held over a cup placed in water of the same temperature, and containing the galvanic wires. Both arteries were divided, and the blood allowed to flow into the cup; a thermometer, raised to 96°, being at the same moment placed in the cup between the wires. In a quarter of a minute af- ter the blood began to flow, the thermometer rose to 98°, in half a minute afterwards to 99°. In a quarter of a minute more it had fallen to 98°, in a quarter of a minute it was still 98°, in half a mi' 181 nute more 97°> in a quarter of a minute more, that is, two minutes after the blood began to flow, it returned to 96°, after this it continued gradually to fall. The low temperature of this animal, and the evolution of caloric, being less than in Expe- riment 65, probably arose from the same cause. I wished to ascertain, whether galvanism oc- casions a similar evolution of caloric from venous blood. Exp. 68. Blood was taken from the arm of a person, whose temperature, as appeared by put- ting the bulb of a thermometer into the mouth, was 98°. The blood was received into a cup placed in water of the same temperature, into which Avere put the wires from the galvanic trough. The thermometer, raised to 98°, was put into the cup as soon as the blood began to flow into it. It continued gradually to sink, at no moment giv- ing the least indication of the evolution of caloric. This experiment was repeated in the same way, and with the same result. I wished to try the effect of galvanism on blood returning from the viscera. Exp. 69. For this purpose the vena cava of a young rabbit, whose temperature Avas rather above 100°, was opened, and the blood from it al- lowed to flow into a cup, placed in water of rather a higher temperature than 100° ; the thermome- ter, raised to the same temperature, and the gal- vanic Avires being placed in a cup, while the blood 182 Was flowing. No evolution of caloric whatever took place. As the greater part of the bulb of the thermometer in this experiment remained un- covered, the quantity of blood obtained from this rabbit being small, the experiment was repeated on a cat. Exp. 70. The temperature of the cat was 97«° This experiment was conducted in exactly the same way as the last, except that the tempera- ture of the water was 97°; and the thermometer, at the time of its introduction into the cup, raised to the same degree. The blood flowed freely into the cup. The thermometer indicated no evolu- tion of caloric. The galvanism produced the same visible effects on the venous as it had done on the arterial blood, except that the colour of the former remained unchanged. Experiments 65 and 67 prove, that by the poAver of galvanism, caloric is evolved from ar- terial blood. When this circumstance is com- pared with the experiments proving the power of galvanism in effecting the formation of the secreted fluids, and with the fact, that the tem- perature of animals is lessened by impairing the vigour, or destroying part of the nervous system, it will be admitted to afford a strong argument in favour of the identity of the nervous influence and galvanism. I need hardly observe, that no caloric being evolved by the power of galvanism from venous blood, that is, blood which has al- 183 ready undergone the secreting power, is an ad- ditional argument in favour of this opinion. In the seventh volume of the Medico-Chirur- gical Transactions, Mr. Henry Earle notices many cases of palsy, in which the temperature of the paralytic limb, although the pulse was good, was lower than that of the rest of the body. In the first case Avhich he mentions, he found, that passing the electric fluid through the limb, raised its temperature. I am sorry that I have not had an opportunity of repeating this experiment, either Avith electricity or galvanism, having not met Avith any case of palsy, since I read Mr. Earle's paper, in which the tempera- ture was lessened. Exp. 71 • By the foregoing experiments the idea is suggested that some gaseous fluid pro- bably escapes from arterial blood, soon after it leaves the vessel. To ascertain whether this is the case, a glass of such a shape that the small- est globule of air could be seen in it, was filled with and inverted over mercury. A considera- ble part of the femoral artery of a large rabbit, whose sensibility had been nearly destroyed by opium, was then exposed and divided under the glass. The blood immediately rose into the glass, and was allowed to remain undisturbed for a quarter of an hour, but no gaseous fluid was disengaged from it. In performing this ex- periment, if great care be not taken, the hair of 184 the animal and hands of the assistants may con- vey a little air under the glass, by which we were repeatedly foiled in making the experiment. The artery must not be held deep in the mercury, else the weight of the metal, by compressing it, will prevent the escape of the blood. The glass into which the blood was received, rose only about an inch and a half above the sur- face of the mercury. Had it risen high enough to take off any considerable part of the pressure of the atmosphere, the experiment, it is evident, would not have been a fair one. What elastic fluids may be disengaged from arterial blood, when that pressure is removed from it, is a dif- ferent question. It appears from this experiment, that the difference of the effect of galvanism on this blood at the moment it leaves the vessel, and two minutes after it has left it, does not arise from the escape of any gaseous fluid. When speaking of the order in Avhich the functions of the animal body cease in dying, I shall have occasion to relate some additional experiments on animal temperature. 185 CHAP. IX. On the use of the Ganglions. It appears from experiments related in the first and second chapters of the present part of this treatise, that the motion of the heart, though in- dependent of, may be influenced through, every part of the brain and spinal marrow. It seems also ascertained, by experiments related in the same chapters, that the blood vessels bear the same relation to the nervous system with the heart. Their power is equally independent of this system, and they are influenced in the same way by agents acting through it. We cannot, we have seen, affect the muscles of voluntary motion in the extremities, by agents applied to the upper parts of the brain, yet the vessels of their most extreme parts obey agents applied even to the upper surface of this organ. It appears from experiments related in Chap- ter VI, that the muscular power of the alimen- _ tary canal is also independent of the nervous ^ system. It is impossible, for reasons which have been laid before the reader, to ascertain, by experiments similar to those relating to the heart and blood vessels, whether the alimentary canal also is subject to the influence of every part of the brain and spinal marrow. With re: 26 186 spect to it, therefore, I attempted, in the second Section of Chapter VII, to determine this point in a different way. Although the muscular power of the alimentary canal is independent of the brain and spinal marrow, its secreting power, we have found, is wholly dependent on them; I en- deavoured, therefore, to ascertain whether it is subject to every part of these organs, by with- drawing the influence of different parts of them from the most important part of it, the stomach; and we have seen, that when this organ is de- prived of the influence of any considerable part either of the brain or spinal marrow, its secret- ing function is deranged, the derangement being proportioned to the importance and extent of the part whose influence has been withdrawn. The stomach, therefore, like the heart, is capable of being influenced by every part of the brain and spinal marroAV. Here the question arises, by what means is the one set of organs subjected to the influence of every part of the other. We cannot suppose that the former receive nerves from every part of the brain and spinal marrow. We know, indeed, that no organ does so. The following seems to be the state of the question. We see some parts influenced by every part of the brain and spinal marrow; others, only by small parts of them. In the latter instances, we see directly proceeding from those small parts, the nerves of the parts 187 influenced. In the former instances, namely, Avhere it is found that the part is influenced by all parts of the brain and spinal marrow, Ave do not, in any case, see nerves going directly from all parts of these organs to the part influenced, but Ave always see this part receiving nerves from a chain of ganglions, to which nerves from all parts of the brain and spinal marrow are sent. It is, therefore, evident from direct experiments, that the nerves issuing from ganglions convey to the parts, to Avhich they send nerves, the influence of all the nerves which terminate in these bodies. Such then is the relation which the most im- portant organs of involuntary motion bear to the brain and spinal marrow. Their powers are in- dependent of both, yet they are subjected to the influence of every part of both, communicated through the medium of the ganglions; and when we see the other organs of involuntary motion equally independent of the brain and spinal marrow, and supplied with nerves from gang- lions in the same way with them, it is allow- able to infer that they bear the same relation to the brain and spinal marrow. Thus it would appear, that the ganglions may be regarded as a secondary centre of nervous influence, receiv- ing supplies from all parts of the brain and spinal marrow, and conveying to certain organs the influence of all those parts. If the nervous influence of the thoracic and ab- 188 dominal viscera be thus supplied from a common source, why, in affections of the spinal marrow, it may be said, is the breathing most affected when the disease is in the dorsal portion of this organ, and the action of the bladder and rectum most affected when its chief seat is in the lumbar portion ? This arises from the muscles of respira- tion deriving their nerves from the dorsal portion, and the abdominal muscles deriving their nerves from the lumbar portion of the spinal marrow. The latter muscles generally excite, or at least increase, the action of the bladder and rectum, by pressing them against their contents, and also by this pressure contribute mechanically to expel their contents. Thus, in the above cases, in ad- dition to the failure of nervous influence in the viscera, there is a failure of excitement in the muscles of voluntary motion, which conspire with these viscera in certain parts of their functions. We can trace the communications of nerves is- suing from the great chain of ganglions, placed, it would seem, to facilitate these communications in the centre of the animal system, with all the nerves of the body. And many circumstances, regarded by anatomists as anomalous, namely, nerves becoming larger after they appear to send off branches, apparently taking a retrograde course, &c. are readily explained, if we admit that nerves, arising from ganglions, join and again separate from those proceeding in an opposite 189 direction from the brain and spinal marrow. It is worthy of remark that none of these anomalous appearances are observed in the lower parts of the body and inferior extremities, where the ganglian must take the same course with the other nerves. Bichat, although his opinions respecting the use of the ganglions are very different from those which I have been led to form, and indeed wholly inconsistent with the results of the fore- going experiments, was induced from his obser- vation of the situation and distribution of the ganglions and their nerves, to regard them as the centres of minute nervous systems. Comparing all that has been said, Ave have reason to believe, that the system of ganglian nerves is quite as extensive as that of the nerves proceeding directly from the brain and spinal marrow. We every where find blood vessels, which we have seen receive the nervous influence through the ganglions; and, indeed, in the larger vessels, we can often trace the ganglian nerves attached to and supplying them. The following case, related by Dr. Parry, in the 139th page of his Treatise on the Arterial Pulse, might alone be regarded as proving the existence of two sets of nerves in the extremities ; the one supplying the muscles of voluntary motion, the other, the powers supporting the circulation ; and striking- ly illustrates Avhat has been said on this subject. " I have seen," he observes, " a total loss of pulse 190 in one arm with coldness, but complete power of motion in that part; while the other arm was warm, and possessed a perfectly good pulse, but had lost all power of voluntary motion." From the foregoing observations the question arises, for what purpose has nature thus combined the influence of every part of the brain and spi- nal marrow to bestow it on particular parts ? This question appears to be answered by the ex- periments which shew, that when the influence of any considerable part, either of the brain or spinal marrow, is withdrawn from secreting sur- faces, the secreting power is deranged. This we have seen ascertained by repeated experi- ments, both with respect to the surface of the stomach and lungs. Among the secretions I ranked the evolution of caloric, although not tak- ing place on any particular surface, because it appeared to be performed by the same power acting on the same fluid; and because, like se- creted fluids, it fails when any considerable part of the influence of the brain or spinal marrow is Avithdrawn. Admitting, it may be said, that the due per- formance of secretion requires the united power of all parts of the brain and spinal marrow, and that Ave may, therefore, explain why their united influence is bestowed on secreting surfaces; the question still remains, why should their united influence be bestoAved also on the muscles of in- voluntary motion ? 191 It is evident that there could be no occasional increase of the secretions, were not the sangui- ferous system capable of being stimulated by the same influence which operates in the formation of the secreted fluids. The increase of secreting power in any part Avould be in vain, were there not at the same time a corresponding increase in the supply of the fluids on which it operates. A similar observation applies to the excretory mus- cles as far as they are muscles of involuntary mo- tion. The same increase of nervous influence which occasions an increased flow of secreted fluids, excites these muscles to carry off the in- creased quantity. Nature does not seem to trust this to the increase of stimulus occasioned by the increased flow of the secreted fluid, which we have reason to believe from the modus operandi of certain causes of inflammation, Avould often oc- casion morbid distension.* Is it not more than probable that the same laws obtain in the absor- bent system ? Now, the vascular system and the muscles of excretion, if in them we include the alimentary canal, comprehend all the muscles which are supplied with nerves from the gang- lions, unless we regard the iris as a muscle. The state of this organ is quite anomalous in the animal oeconomy, being one of involuntary mo- tion, always stimulated through the medium of the nervous system. * See Chap. XII. art. Inflammation. 192 Thus, we see the necessity of every part of the function which the ganglions appear to perform. A combination of the whole nervous influence is necessary for the due formation of the secreted fluids, and that there may be, under all circum- stances, both a due supply of the fluids to be acted upon, and a due removal of those prepared, whether for the functions of life or for the pur- pose of being thrown out of the system, it is necessary, as appears from what has just been said, that the muscles which answer these pur- poses should be subjected to the influence by which the secreted fluids are prepared.* The function of secretion, it is evident, requires a more regular supply of fluids than could have been obtained, had the usual action of the vessels depended on the nervous system, which is sub- ject to continual variation; but had not this sys- tem been capable of stimulating the vessels, no change in it could have occasioned an increased flow of secreted fluids. Thus, it is necessary that the poAver of the sanguiferous should be inde- pendent of the nervous system, yet capable of be- ing influenced by it; as it is ascertained to be * The constant presence of fluids in secreting surfaces ap- pears to solicit a continual supply of nervous influence to them, so that they go on during our sleeping as well as wak- ing hours. The more copious the supply of fluids to secret- ing surfaces, we find the secreting power the greater, and vice versa. 193 by the experiments related in the first and second chapters of the present part of this Treatise. That the reader may see how far the observa- tions of the anatomist correspond with the result of the preceding experiments, I shall beg leave to recall to his mind the nervous connections of the ganglions ; by which he will find that they may receive the influence of every part of the brain and spinal marrow, and communicate that influence to every part of the body. The great sympathetic nerve receives nerves from every part of the spinal marrow, being largest near the middle of the spine, and becoming smaller as it ascends and descends, forming ganglia, which give out nerves on all sides. When these circum- stances are compared with the fact of its convey- ing the influence of every part of the spinal mar- row, Ave cannot, I think, hesitate to regard it as arising from this organ; especially as its slender communications with the nerves of the head pre- sent the appearance of its gradual termination in that direction. This inference is further strength- ened by other means being provided for convey- ing the influence of the brain to the thoracic and abdominal viscera. The parvagum of the eighth pair of nerves, we have seen from the effects of dividing it, performs this office; for whiclj it is admirably fitted, by its numerous and extensive communications with the ganglions aud plexuses 27 194 of the great sympathetic. After various connec- tions with those in the neck and chest, it sends a large branch to the stomach, whose filaments are intermixed on this organ Avith those of nerves sent by several of the abdominal plexuses; and at length terminates in forming with the splanch- nic branches of the sympathetic the great semilu- nar ganglion, called the caeliac ganglia from its situation, and its being composed of many small, irregularly shaped ganglions of different sizes. From these ganglions, so formed, many nerves issue, forming plexuses on the different large ar- teries, from which they derive their names. Nerves, from these plexuses alone, or intermixed Avith other branches from the sympathetic nerves, supply the whole abdominal viscera. Before the sympathetic nerves finish their course by uniting on the os coccygis, they form ganglions in the loins, which send branches to thtf lumbar nerves; and others in the pelvis, which send branches to the sacral nerves; thus forming communications between the ganglian system and the nerves of the lower extremities. The nerves of the upper extremities commu- nicate with this system, both by means of the middle cervical ganglion, and through the sym- pathetic nerves, by branches from the second and third intercostal nerves which go to these extremities. The ganglian system communicates by branches 195 of the sympathetic nerves with the internal nerves of the head. One branch is sent to the second branch of the fifth pair before it leaves the cra- nium, and one, two, or sometimes three, small filaments to the sixth pair, and a branch to the portio dura of the seventh pair, at the under part of the ear. These connecting branches are generally regarded as proceeding from the nerves of the head, but for reasons already assigned, we must, as far as I am capable of judging, agree with those writers who regard them as proceed- ing from the sympathetic nerves. The extensive connections of those nerves with the eighth pair have already been mentioned. The external nerves of the head and neck, namely, the higher spinal nerves, communicate Avith the cervical ganglions; and lastly, the gang- Han system communicates with the external parts of the trunk by means of the connections of the sympathetic with the spinal nerves which supply those parts.* Thus, the sympathetic nerves, conveying the influence of the spinal marrow, and the par vagum, that of the brain, unite in forming the ganglions, which with their plexuses, constitute * Here we have reason to believe a double communication takes place, the spinal nerves conveying to the sympathetic the influence of the spinal marrow, and the sympathetic send- ing with them to the parts to which they are distributed, filaments conveying the influence of the ganglian system. 196 a secondary centre of nervous influence, a chan- nel through which the influence of every part of the brain and spinal marroAV flows, to be be- stowed on the thoracic and abdominal viscera, on the vessels and all secreting surfaces; the most important of which parts, we have by di- rect experiment found subjected to every part of the brain and spinal marrow. In one of the treatises referred to in the Report of the National Institute of France, that by Dr. Johnstone, the reader will find many facts respect- ing the ganglions and the distribution of their nerves, which he collected with much assiduity for the purpose of supporting his opinions re- specting the uses of these organs. He adopted the opinion of Winslow and other physiologists, that the "ganglions seem analogous to the brain in their office ; subordinate springs and reservoirs of nervous power," he continues," they seem ca- pable of dispensing it, long after all communica- tion with the brain is cut off. And, although they ultimately depend on the brain for its emanations, it appears from facts, that dependence is far from being immediate and instantaneous."* The rea- der will readily perceive that this opinion is in- compatible with many of the facts which have been * Med. Essays and Obs. by J. Johnstone. M. D. Physi- cian in Worcester, 1795, p. 85. 197 laid before him. Dr. Johnstone was led to infer that the ganglions can, for a certain time, perform the office of the brain, by ascribing to the power of nervous influence many phenomena which seem wholly to depend on the power of the muscular fibre itself.* To the above opinion, adopted from his prede- cessors, Dr. Johnstone added the following opi- nion of his OAvn, which he endeavours to support by direct experiment, as Avell as by an accurate and extensive review of the phenomena of the nervous system. " May we not reasonably con- clude," he observes, " that ganglions are the in- struments by which the motions of the heart and intestines are from the earliest to the latest pe- riods of animal life rendered uniformly involun- tary ?"f Dr. Johnstone's experiments, an account of which is given in the 25th and following pages of the work just quoted, and other experiments of a similar nature to Avhich he refers, of Haller, Whytt, &c. were made with a view to prove that it is impossible to affect the action of the heart by stimuli applied to the brain and spinal marrow, These physiologists appear to have been deceived in the result of their experiments on this subject by two circumstances. They did not employ the * Chap. VI. t The above-mentioned Treatise, p. 16. 198 precaution of preventing the action of the muscles of voluntary motion, which renders it impossible to judge of the effect of the stimulus on the heart: and they were not aware that the heart will not obey a stimulus applied to the brain and spinal marrow, however powerful, unless it be applied to a portion of considerable extent. Any person who attends to these precautions will find, that the heart is not only as easily stimulated through the brain and spinal marrow as the muscles of vo- luntary motion; but that it may be stimulated through them for a considerable time after these muscles can no longer be influenced in this way; proving that the ganglions oppose no obstacle to the influence of the brain and spinal marrow, be- ing extended to the muscles of involuntary mo- tion. We can surely be at no loss to account for the action of these muscles being involuntary, when we know that they are all exposed to the constant or constantly renewed action of stimuli, over which the will has no power. Besides, the ac- tion of these muscles produces no sensible effect. We will to move a limb, not to excite a muscle. We wish to handle, for example, and on trial find that we can move our fingers; but what act of volition can we perform through the medium of the heart or blood vessels ? If we had no Avish to handle, the muscles of the fingers of course would never become subject to the will. It de- 199 serves to be remarked, that the will influences the rectum and bladder, the only internal organs Avhich can assist in accomplishing an end desired. It seems to be superfluous after the experiments which have been related, to say any thing in re- futation of the opinion of Bichat, and that the ganglions are centres of nervous influence, inde- pendent of the brain and spinal marrow. " Les nerfs des ganglions ne peuvent transmettre Pac- tion cerebrale; car nous avons vu que le systeme nerveux partant de ces corps, doit etre considere comme parfaitement independant du systeme ner- veux cerebral; que le grand sympathique ne tire point son origine du cerveau, de la moelle epini- ere ou des nerfs de la vie animale ; que cette ori- gine est exclusivement dans les ganglions; que ce nerf n'existe meme point, a proprement par- ler, qu'il n'est qu'un ensemble d'autant de petits systemes nerveux qu'il y a de ganglions, lesquels sont des centres particuliers de la vie organique, analogues au grand et unique centre nerveux de la vie animale, qui est le cerveau." Recherches Physiologiques sur la vie et la mort par Xav. Bichat, page 355 & seq. 200 CHAP. X. On the relation which the different functions of the animal body bear to each other, and the or- der in which they cease in dying. It is evident that before we can attempt to trace the relation which the functions bear to each other, and the order in which they cease in dy- ing, we must be able clearly to define them. It appears from the experiments Avhich I have had occasion to relate or refer to, that in the more perfect animals there a/e three vital poAvers not directly depending on each other, the sensorial, the nervous and the muscular powers. With regard to the last of these, it is readily distinguished by its effects from the nervous and sensorial powers, and depends, we have seen, on the mechanism of the muscular fibre itself.* When the mechanism of that fibre is deranged, its power is destroyed; and nothing else can de stroy it. The nervous power, it appears, from many of the experiments which havC*been related, acts only as a stimulus to the muscular fibre. It per- forms the more complicated functions of preparing the various secreted fluids, and causing an evo- * Chap. III. and VI. 201 lution of caloric from the blood; and is the means by which impressions are conveyed to the sen- sorium. The sensorial power, as far as it is concerned in the functions of mere animal life, appears to consist Avholly in receiving impressions from, and communicating them to the nervous power. The seat of the sensorial and nervous powers is not so well defined as that of the muscular power. M. le Grallois appears to regard the brain as the seat of the one, and the spinal mar- row as that of the other; but many observations seem to oppose this opinion. Nerves proceeding wholly from the brain exhibit all the phenomena of nervous power, properly so called; and that the spinal marrow possesses sensorial power appears from very simple experiments. Exp. 72. If, after the spinal marrow of a rab- bit is divided about the middle, one of the hind legs be wounded, not only the wounded leg is moved, but the other hind leg also, demonstrating that there is a power residing in the spinal mar- row which receives the impression made on the nerves of the one leg and communicates it to those of the other. M. le Gallois makes many similar observations. In the cold blooded animal the same thing is observed in a greater degree. For some hours after decapitation the frog will often sit in its usual position, and appear sensible to an injury inflicted on any part of it. It is evident 28 202 from many observations, however, that the sen- sorial power chiefly resides in the brain, and the nervous in the spinal marrow. If these powers, it may be said, are thus blend- ed in their organs, what proof have Ave of their being distinct powers ? This proof I think we shall find by carefully observing the process of dying, of which, what we call death appears to be only the first stage. We shall also, I think, by the same means, clearly perceive the way in which all the foregoing powers are so connected in the more perfect animals, that none can long exist without the others. At the instant of death, it is evident, the sen- sorial power ceases. No impression made on any part of the body is perceived or followed by any act of volition. It is equally evident to the physiologist that the muscular poAver still re- mains. If the heart, or muscles of voluntary motion be stimulated, they still possess the pow- er of contraction, which is only lost by sIoav de- grees, a considerable time after the sensorial pow- er has ceased to exist. It is also evident to the physiologist, that some part of the nervous power still exists, for if the nerves themselves, or those parts of the brain or spinal marrow from which they originate, be irritated, the corresponding muscles are thrown into action; a proof that the extinction of the sensorial powers does not de- pend on the nerves having become incapable of 203 conveying impressions. Is the nervous power still capable of performing its other functions? Whether it is capable of conveying impressions to the sensorium we have, of course, no means of judging, where no sensorium exists; but if we find it capable of all its other functions, we may infer that it possesses this function also, and that the cause of its non-appearance is the known fail- ure of the poAver which must*conspire to make this part of its functions sensible. The question then which we have to consider here is, can the nervous poAver effect the formation of the secreted fluids, and occasion an evolution of caloric from the blood, as Ave find it can excite the muscles, af- ter the destruction of the sensorial power ? I have already had occasion to refer to Mr. Hunter's observations respecting the digestion of the stomach after death. It is perhaps superflu- ous to observe, that this is not to be regarded as any vital action. It is a mere chemical process. But Mr. Hunter, as appears from the following observations, suspected that a truly vital action continues m the stomach for some time after what is called death. " This is exactly the case with the experiments of Spallanzani, which although they prove that meat was digested in the stomach after the animal was killed, Avhich no one doubt- ed," that is, no one doubted that the gastric juice already in the stomach would continue to perform its office there, " yet are not at all calculated to 204 shew that the stomach itself may be digested. In fact the manner in which they were managed rather tended to prevent that. effect from taking place, the gastric juice having substances intro- duced on which it could act, was less likely to affect the coats of the stomach. That the diges- tion was not carried on merely by the effects of the gastric juice secreted before death, is evident from his own account, some of the food Avhich had been introduced and digested being found in the duodenum; a thing which could not have happened if a cessation of the actions of life in the involuntary parts had taken place when visi- ble life terminated. There had been an action and most probably a secretion in the stomach."* It appeared to me that this conjecture of Mr. Hunter might be reduced to the test of experi- ment, by dividing immediately after death the eighth pair of nerves, which seems at once to destroy the secretion of gastric juice. I shall use the words death and killed in the usual ac- ceptation, not implying the ceasing of all the functions. After this explanation no ambiguity can arise from the use of these terms. We are not, it is evident, to expect that any great secretion of gastric juice can take place after death, or conse- quently that any great difference can be observed between the food in the stomach of an animal * Observations on the Animal (Economy, page 181. 205 in which the eighth pair of nerves has been di- vided immediately after death, and one in which they are left entire; and many circumstances which we cannot estimate, particularly there being more gastric juice in the stomach of the one animal than the other, at the time they are killed, or one having eaten more than the other, must influence the result. It will not answer the purpose, it is evident, to confine the animals to the same quan- tity of food, because the stomach of that which is most hungry will digest it most quickly. The quantity of old food in the stomach also influ- ences the result. The question, therefore, can only be determined by making the experiment on a large scale, to which, as it is made on the dead animal, there can be no objection. Exp. 73. This experiment was made on twen- ty-six rabbits ; eight full grown, eight half grown, six two months old, and four one month old. They were made to fast for sixteen hours, at the end of this time allowed to eat as much cabbage as they chose, and then killed by a blow on the occiput. Immediately after death the eighth pair of nerves was divided in one half of those of each description, and they were all allowed to lie undisturbed for about twenty-two hours. I need hardly observe that the experiment was not made on all at the same time, but care was taken that the circumstances of it should be the same in all. The stomachs were then laid open, and those of 20t> the rabbits of the same age, who had eaten mo*t nearly the same quantity, were compared together. The result was, that in twelve pairs the food was most digested in those animals whose nerves Avere left entire. In one pair it was most digested in the animal whose nerves had been divided. In several of those whose nerves had been divided, the cabbage appeared quite fresh and green. This did not happen in any whose nerves were left entire. In these the colour was always chang- ed more or less to a brown. The difference iu the state of the cabbage was sometimes more sen- sible to the touch than to the eye, that least digest- ed feeling hardest. This experiment, at the same time that it proves the accuracy of Mr. Hunter's conjecture, shews more than any experiment made on the living animal could do, Iioav quickly the secretion of gastric juice is destroyed by the division of the eighth pair of nerves in the neck. It is remarkable that the division of these nerves after death almost always produced the same ap- pearance of dark coloured patches upon the sur- face of the lungs, but generally in a less degree, observed from it when the operation had been per- formed during the life of the animal; an effect, equally with the state of the stomach, demon- strating that some of the involuntary functions continue for a certain time after visible death. These patches now and then appear in the lungs of an animal whose nerves are entire, after it has 207 lain dead for some time; but much less frequent- ly, and to a much less degree, than when the nerves have been divided immediately after death. The appearance of dark red patches on the surface of the lungs, we have seen, is always ob- served to a great degree Avhen the eighth pair of nerves have been divided during the life of the animal, and it has survived the operation many hours. It may be regarded, and is mentioned by various physiologists, as the characteristic effect of the operation on this organ. The congestion of the lungs, which is also an uniform conse^ quence of it, appears under many other circum- stances, but I know of no other in which there is an appearance like this patching, except, as I have just mentioned, that a certain degree of it, or rather something like it, now and then appears in the lungs of the entire animal after it has lain dead for many hours. In the living animal it Avas always proportioned to the degree in which the secreting power of the lungs was deranged, appearing to the greatest degree when the con- gestion of the lungs was greatest; and not ap- pearing at all, although the eighth pair of nerves had been divided, when the breathing was ren- dered free, and the congestion prevented by gal- vanism. Exp. 74. It Avas suggested, that, by the power of galvanism the degree of digestion which takes place after death might perhaps be increased. 208 But we could not by any means cause the gal- vanism to produce any sensible effect on the rab- bit after death, except for a very short time; sometimes no effect could be produced longer than five minutes, and in no instance was the ef- fect sensible beyond about a quarter of an hour, even with the assistance of artificial respiration and a very powerful galvanic apparatus; and during these short times its effects were constant- ly becoming weaker. We could never even suc- ceed in producing the slightest appearance of in- flammation either in the stomach or bowels, an ef- fect which uniformly attends digestion supported by galvanism. From these circumstances, and from what I have said above, respecting the dif- ficulty of ascertaining whether or not a slight ad- ditional degree of digestion has taken place, I need hardly say, that it was impossible to ascer- tain whether or not any change on the food was effected in this experiment. I think there is reason to believe, that although the galvanic influence could be supported for a longer time after death, it would occasion no in- crease of secretion. No inflammation occurring seems to arise from there being no increase of vis a tergo, that is, no increased action in the larger vessels. Thus, whatever increase of nervous in- fluence there may be, there can be no increased supply of fluids for it to act upon, without which it is evident there can be no increased secretion. 209 What then, it may be asked, occasions any sup- ply of fluids to secreting surfaces, and thus ena- bles the remaining nervous influence to produce any secreted fluid after death ? The result of the following experiment appears to afford a ready answer to this question. Exp. 75. A rabbit, about two months old, was killed by a Woav on the occiput. The chest was then laid open and a ligature thrown round the aorta. Part of the mesentery was now brought before a microscope, and the blood in its vessels seen both by Mr. Sheppard and myself, moving with great velocity. By examining different parts of it, and chusing those which had not been previously disturbed, and consequently still re- tained some warmth, we found the circulation, in the smaller vessels, going on with rapidity for a quarter of an hour after the aorta had been secured, and an irregular motion of the blood in these vessels was evident for twenty minutes longer, the blood stopping and going on, and sometimes moving backwards and forwards in the same vessel. This could be distinctly seen long after the part had become quite cold. This experiment was performed in the sun-shine, in the open air, where there happened to be a good deal of wind, and the exposed part of the mesen- tery quickly became parched; which, as we found from other trials, destroyed the motion of the 29 210 blood in the capillaries long before it naturally ceases. Full-grown rabbits are bad subjects for this experiment, on account of an accumulation of fat which takes place in the mesentery, and obscures the vessels. Rabbits about six weeks old, when they have been fed for some time on green, meat, are generally thin, and consequently the best sub- jects for it. Exp. 76. A dead rabbit, about a month old, whose intestines we had been examining, after having thrown a ligature round all the vessels at- tached to the heart and removed this organ, was thrown aside, with the intestines hanging out through the wound in the parietes of the abdomen. An hour and a quarter after the heart had been removed, I brought part of the mesentery, which had long been quite cold, before the microscope, and still found the blood in some of the capillary vessels moving freely. I have no doubt that the blood continues to move in the capillaries of a full-grown rabbit, whose temperature will sink much more slowly, for several hours after death. This at the same time accounts for the supply of fluids to secreting surfaces, and for a certain pow- er of the nervous system remaining after death, and when the vis a tergo has wholly ceased, ex- cept as far as it depends on mere elasticity and the action of very small vessels. It seems to be 211 owing to this cause also that the larger arteries of dead animals are found empty.* Hoav readily the continued action of the capillaries must empty them, will be evident when we recollect how much the sum of the areas of the branches of the arteries exceeds the areas of their trunks. I need not observe how inconsistent the result of the foregoing experiment is with the opinion of Doc- tor Parry, and some other physiologists, who maintain that the circulation is supported by the power of the heart alone. Exp. 77- Although it is difficult to ascertain whether galvanism influences the state of the sto- mach after death, the case is very different with respect to the lungs. In them it is easy, from the degree of patching, with precision to ascer- tain the state of the secretions. Here, however, there was no occasion for minute observation, for in nine instances,, in which a stream of gal- vanism was sent through the lungs for about a quarter of an hour after the eighth pair of nerves had been divided immediately after death, all appearance of patching was prevented, the lungs after the animal had lain dead about twenty hours appearing quite sound. It appears from the foregoing experiments that * I cannot agree with Dr. Parry in ascribing this fact to the contractility of the arteries. This may reduce, but it can- not wholly expel their contents. 212 the secreting power continues for some time after the sensorial power has ceased; AAe are now to inquire whether the nervous poAver, uuder the same circumstances, is capable of occasioning an evolution of caloric from the blood. I here con- sider it as proved by experiments already laid before the reader, that the evolution of caloric is a function of the nervous influence. It seems so immediately to depend on the existence of the circulation, and so generally proportioned to its vigour, that we cannot, I think, adopt a better means of ansAvering the question before us, than by ascertaining whether supporting circulation by artificial respiration after death occasions a greater evolution of caloric than takes place when the dead animal is left undisturbed. On this subject there has been great difference of opinion. The following experiments seem to point out how this difference may have arisen, on the supposition that all the experiments which have been made on the subject are correct, which we have every reason to believe them to be. Exp. 78. Two rabbits of the same size were killed by a blow on the occiput, the temperature of the air being 61°, that of both rabbits 104°. The lungs of one were inflated six times, tljose of the other from twenty-six to thirty times in a minute. The temperature of the first in half an hour was 102.25°, in an hour 100°; the tempe- 213 rature of the second at the end of half an hour was 101.5°, at the end of an hour 98°. It is evident that all the air thrown into the lungs, beyond What is necessary to effect the pro- per change in the blood, must tend to reduce the temperature in proportion as that of the air is less than that of the animal. The living animal re- ceives but little air into the lungs in one inspira- tion. It is impossible in the dead animal to throw in the quantity which the blood still de- mands and no more. The following experiments, in which Mr. Shep- pard was so good as to assist me, as indeed he did in all the experiments which I made on this part of the subject, strikingly illustrate these observa- tions. Exp. 79. Two rabbits were chosen of the same size, and each of the temperature of 102.5°. They were killed in the usual way, in the tempe- rature of 65° ; one was left undisturbed. In the other, the lungs were inflated about thirty times in a minute. In half an hour the temperature of the undisturbed rabbit was 98-75°, while that of the other was only 98.5°. In the last the lungs were then inflated only about twelve times in a minute. In half an hour its temperature was 96°, so that it had lost 2.5°, while that of the other left undisturbed had in the same time sunk to 95.25°, so that it had lost 3.5. Exp. 80. Two rabbits were killed in a tempe- 214 rature of 61.5.° The temperature of the one was 106°, of the other 103, the lungs of the first were inflated twelve times in the minute, the other was left undisturbed. In half an hour the first had lost 3.5°, its temperature being 102.5°. The other in the same time had last 4°, its temperature being 99s. The first being of the highest tempe- rature, would have cooled fastest had both been undisturbed, although probably not in a sensible degree. I may here observe, that it always hap- pened in the course of such experiments as those which I am relating, that the temperature of the room varied, but as the experiment was always made on both rabbits at the same time, and placed together, this could not influence the result, and is therefore unnoticed. The lungs of the first of the above rabbits were now inflated at the rate of from twenty-six to thirty times in a minute. At the end of half an hour its temperature was 98°, that of the other at the same time being 94.5°, so that each had now cooled 4.5°, the evolution of caloric in consequence of the inflation of the lungs being here sufficient to counteract the cooling effect of the rapid change of air, and no more. In one experiment of this kind, in which the lungs were inflated only a few times in a minute, we found that the temperature had risen nearly 1° between two of the examinations. While I was making experiments on this sub- ject in Worcester, Mr. Hastings, was, without my 215 knowledge, making similar experiments at Edin- burgh. He shewed me the detail of several, which prove that throwing air into the lungs of the dead rabbit about fifteen times in a minute, occasions it to cool more slowly than it would otherwise do. In one of his experiments the rabbit, in which artificial breathing was per- formed, cooled only 4°, while that which was left undisturbed cooled 7.5°. This was the greatest difference he observed. He frequently saw the thermometer rise a little in those ani- mals in which the lungs were inflated after death. In those in which they were not inflated the cooling was always uniform. There can be no doubt, I think, from the pre- ceding experiments, that when the lungs are not inflated so frequently as to constitute a power- fully cooling process, their inflation, by occasion- ing an evolution of caloric after what Ave call death, retards the cooling of the animal. My next object was to ascertain how far the evolution of caloric, after death, is influenced by the destruction of the brain and spinal marrow. Exp. 81. Two rabbits of the same size, whose temperature was 98°, were killed in the usual way. In one, immediately after death, the brain and spinal marrow were destroyed by introduc- ing, through a hole in the cranium, a wire of nearly the same diameter with the cavity of the 216 spine, repeatedly pushing it on to the end of this cavity, and then moving it about for some time in the cavity of the cranium. The other rabbit was left entire. A hole was made about the centre of the abdominal muscles in each, to ad- mit of a thermometer being introduced into the cavity of the abdomen. They were placed near each other in a temperature of 50°. During the first twenty minutes each lost exactly 4°, and they both lost, during the succeeding three quarters of an hour, just 2° during each quarter. Something, which we could not ascertain, accelerated the rate of cooling during the next quarter, and so exactly did it correspond in both rabbits, that each lost during this quarter 2.5. After this their tempe- rature diminished more slowly, and still more so of course as it approached more nearly to that of the air, but still in both it Avas found to corres- pond. At the end of a hundred and ten minutes the temperature of both rabbits was 84°. Exp. 82. The foregoing experiment Avas re- peated, with the difference that in both rabbits the lungs were inflated; but we could not per- ceive that the one rabbit cooled faster than the other. Exp. 83. Two rabbits of the same size and temperature, being killed in the usual way, in the one the brain and spinal marrow were wholly removed, the other being left entire. 217 In both the lungs Avere inflated. We could not perceive that the one cooled faster than the other. I was particularly careful in repeating these experiments, because they appear at first view to contradict the inferences of Mr. Brodie, to whose labours this part of physiology owes so much. It will appear, however, from what I am about to say, that their result is perfectly consistent with the doctrine maintained by him. It appears from the foregoing experiments, that after the destruction of the sensorial, the nervous power is still capable of performing all its func- tions, except that it can no longer give evidence of conveying impressions to the sensorial power, the necessary consequence of the destruction of this power. On comparing these experiments, however, a considerable difficulty presents itself. We have seen it ascertained by those on digestion, that the brain and spinal marrow retain sufficient power after visible death to form secreted fluids. Yet it would appear from the experiments ou temperature, that the influence of the brain and spinal marrow has no effect under the same cir- cumstances in promoting the evolution of caloric, although it is evident that the system still retains the power of evolving it, and from former expe- riments, that this power depends on the state of the nervous system. The secreted fluids are no longer formed if the influence of the brain be withv 30 218 drawn, the evolution of caloric takes place in the same way whether the influence of both the brain and spinal marrow be withdrawn or not. A well-known fact appears to remove the dif- ficulty. Although we have reason to believe, 1. think, from every observation on the subject, that the brain and spinal marrow are the only sources of nervous influence; yet it is evident that a cer- tain portion of this influence remains in the nerves when separated from these organs, as appears from the contractions excited in the muscles by irritating their nerves under such circumstances. The muscle. will thus be made to contract as long as any influence remains in the nerve, but this being once exhausted, the nerve has no means of renewing it. Now, the first nervous influence which is employed in the stomach after death is of course that already in its nerves. This being exhausted, the brain and spinal marrow are call- ed upon for a further supply. It is evident that they cannot be long so called upon, because there cannot long be any supply of proper fluids. If then, instead of the nerves which belong to the stomach, the Avhole nerves of the ganglian sys- tem terminated in this organ, there is reason to believe, that the supply of fluids, which takes place after death, would never be sufficient to ex- haust the nervous influence already in its nerves; and consequently, that in that case it would never make any demand on the brain and spinal mar- 219 row; and the same degree of digestion Would take place after death whether the influence of the brain remained or not. Now this is precisely Avhat seems to happen with respect to the tempe- rature after death. As long as Ave can by artifi- cial respiration occasion such a change in the blood as elicits nervous influence, the blood draws it from all the nerves of the ganglion system; and it does not appear, that we can support this change long enough to exhaust the nervous in- fluence already in the nerves, and occasion any further demand for it. It appears from the above experiments, that the greatest evolution of caloric, which can, under ordinary circumstances, be ef- fected after death, is but very inconsiderable. Hence, the result is the same whether the brain and spinal marrow exist or not. The blood has already in the nerves more nervous influence than it can use. Hence also, as I have ascertain- ed by repeated trials, we cannot, under these cir- cumstances, occasion any additional evolution of caloric by galvanism.* The evolution of caloric occasioned by inflating the lungs after death being so small, may arise from our being able but very imperfectly to imi- tate natural respiration. It is true that Ave can imi- * I have considered the cause of the sensation of heat a substance not a quality, because I regard the former as the more probable opinion. I admit that some difficulties re- specting it exist. 220 tate it sufficiently to give the arterial colour to the blood, but we have seen that the evolution of ca- loric does not appear to be connected with the change of colour. It is evidently impossible to proportion the quantity of air thrown in, to the demand for it, which is constantly becoming less, so that we are either supplying too much or too little. In theTormer gase, the superfluous quan- tity can, as far as relates to the temperature, have no other effect but that of reducing it, as happen- ed in the above experiments; but although we could supply air in the due proportion, we should still be very far from being able to imitate natu- ral respiration, from which artificial respiration, among other things, differs in the great pressure to which the lungs are subjected in the latter, in which the ribs and diaphragm are moved by the force of the injected air; whereas in natural re- spiration the ribs and diaphragm being moved by their muscles, the lungs are subjected to no pres- sure but that of the atmosphere. The great di- minution of nervous influence in artificial respi- ration constitutes an essential difference between it and natural breathing. It Avould be worth while, although attended with considerable trou- ble, accurately to ascertain the effects of passing a stream of galvanism through the lungs Avhile artificial respiration is performed. A very decisive experiment by Mr, Brodie, related in addition to the Croonian Lecture above 221 referred to, proves that the change of oxygen gas into carbonic acid gas takes place when the lungs are inflated after decapitation. It remains for us to inquire whence it arises that the nervous and muscular powers never long survive the sensorial power. On the destruction of the sensorial power re- spiration always ceases. M. le Gallois finds a great difficulty in conceiving why respiration should cease on the removal of the brain. 66II est done certain que la vie du tronc n'a son principe immediat ni dans le cerveau, ni dans aucun des visceres de la poitrine et de 1'abdomen; mais il ne l'est pas moins, que tous ces visceres sont indispensables a son entretien. Or, en con- siderant sous quel rapport ils le sont, les faits enonces plus haut prouvent evidemment que, quant au cerveau, les phenomenes mechaniques de la respiration, c'est-a-dire, les mouvemens par lesquels l'animal fait entrer l'air dans ses pou- mons, dependent immediatement de ce viscere. Ainsi, e'est principalement en tant que 1'entretien de la vie depend de la respiration, qu'il depend du cerveau ; ce qui donne lieu a une grande diffi- cult. Les nerfs diaphragmatiques, et tous les autres nerfs de muscles qui servent aux pheno- menes mechaniques de la respiration, prennent naissance dans la moelle epiniere, de la ineme 222 maniere que ceux de tous les autres muscles du tronc. Comment se fait-il done qu'apres la de- capitation, les seuls mouvemens inspiratoires soient aneantis, et que les autres subsistent ? C'est la, a mon sens, un des grands mysteres de la puissance nerveuse; mystere qui sera devoile tot ou tard, et dont la decouverte jettera la plus vive lumiere sur le mechanisme des fonctions de cette merveilleuse puissance." This difficulty appears to me to arise from his having regarded respiration as a function wholly depending on a combination of the nervous and muscular powers; whereas it seems evident, I think, that the sensorial power also shares in it. The muscles of respiration are, in the strictest sense of the word, muscles of voluntary motion; we can at pleasure interrupt, renew, accelerate, or retard their action ; and, if we cannot wholly pre- vent it, it is for the same reason that we cannot prevent the action of the muscles of the arm, Avhen fire is applied to the fingers. The sensation Occa- sioned by the interruption of a supply of air to the lungs is greater than can be voluntarily borne. Respiration continues in sleep for the same reason that we turn ourselves in sleep when our posture becomes uneasy. It continues in apoplexy for the same reason that the patient ge- nerally moves his limbs if they are violently ir- ritated. If respiration continues in apoplexy 223 when no irritation of the limbs, however violent, excites the patient to move them; it arises from the interruption of a supply of air to the lungs producing a greater degree of irritation than any other means we can employ. We know instances in which the hand has been voluntarily held in the fire, but we know of none where the breath- ing has been voluntarily discontinued till the lungs were injured. As the insensibility increases in apoplexy, the breathing becomes less frequent; and when the former becomes such that no means can longer excite any degree of feeling, the breathing ceases. By a certain sensation a wish is excited to ex- pand the chest. This is an act of the sensorium. Till this act take place, the nervous, as well as the muscular power, by which its expansion is effected is inert, it is in vain that these powers re- main* if the power which calls them into action be lost. Thus the removal of the brain puts a stop to respiration. It is said that the motions of inspiration must be involuntary, because Ave are in general un- conscious of them ? But do we not become more or less so of all habitual acts of volition? We frequently hear such observations as the fol- lowing ; if I did so, I did it unconsciously. Stop a person who is walking, he cannot tell which leg he last moved; stop a person avIio is playing on an instrument, he cannot tell which fingers he 224 last employed ; yet all such acts are strictly acts of volition. If we are reminded of them we can always interrupt, renew, retard or accelerate them at pleasure. We have no difficulty in perceiving and changing in any way we please the motions of respiration, when we choose to attend to them; but as there is no other act of volition so habitual, there is none so apt to escape our attention. The above explanation of the manner in which the removal of the brain puts a stop to respiration will be readily admitted, I think, when we con- sider to what part of the brain impressions from the lungs are conveyed. It is evidently to the part where the eighth pair of nerves, which sup- plies them, joins that part of the brain from which the spinal marrow originates. Now it appears from the experiments in which M. le Gallois re- moved the brain by slices, that respiration con- tinued till he removed the part of the medulla ob- longata in which those nerves originate, and then instantly ceased. In these experiments, how- ever, the power of the muscles of inspiration and the nervous power which excites them still re- main, as may be easily ascertained by stimuli properly applied to the spinal marrow. It is the influence of the sensorial power which is lost. We cannot, perhaps, have a better instance of the distinct operation of the sensorial, nervous and muscular powers, than in the case before us, although they all here conduce to the same end. 225 We may destroy any one of them and leave the others unimpaired. The destruction of the sen- sation by which we will to inspire, we have just seen, does not destroy the nervous or muscular power employed in inspiration. By means ap- plied to the muscles of inspiration Ave may de- stroy their mechanism without depriving any part of the spinal marrow of its power, or at all im- pairing the above sensation: and we may destroy the nervous influence which excites these mus- cles by destroying a certain part of the spinal marrow, while they, as may be ascertained by the application of stimuli, perfectly retain their vigour, and the sensation which excites the wish to inspire, though as in the last case, useless, re- mains unimpaired: nay, if any two of these pow- ers be destroyed, they leave the remaining power unimpaired. The destruction of the muscles of inspiration, and of the nervous influence which excites them, does not destroy the sensation by which we will to inspire ; nor does the destruc- tion of this sensation and the nervous influence at all impair the power of the muscles ; and we may destroy the sensation in question, and the power of the muscles, without impairing the ner- vous influence which excites them. So far from true is the position of M. le Gallois, that the pow- er on which all the motions of inspiration depend, resides in the medulla oblongata. Much has been Avritten by Whytt and many 31 226 other physiologists, respecting the cause of the first inspiration. I cannot help thinking that the difficulty vanishes, Avhen we regard the muscles of inspiration as merely muscles of voluntary motion. The young animal throws them into action to remove a painful sensation occasioned by the want of that change in the blood, Avhich is produced by the influence of the air in the lungs; a process necessary to the existence of the animal as soon as its connection with the mother ceases, and which can only be effected by expanding the chest, and thus receiving air into the lungs. It seems to be expanded for the first time precisely for the same reason that the foetus changes its position for the first time by acting with the muscles of the trunk and limbs. In both cases he endeavours to remove an uneasy sensation, and nature has given him the power to remove it by calling into action certain mus- cles subjected to the will. The first act of de- glutition, if it does not occur in the foetal state, appears to be an act of precisely the same nature with the first inspiration. In both cases, a cer- tain set of muscles of voluntary motion is throAvn into action to satisfy a craving, which had no existence in that state.* * It may be objected to this view of the first inspiration, that the animal often breathes before a ligature is thrown round the umbilical chord: but we have no reason to believe, that the secondary change, effected in the blood of the foetus 227 When respiration ceases, most of the pulmo- nary vessels and left side of the heart are no longer supplied with their proper stimulus; and feel more directly perhaps the debilitating influ- ence of black blood. Their functions, therefore, begin to fail. In proportion as this happens, the blood accumulates in the lungs, and the right side of the heart experiences an increased dif- ficulty in emptying itself. By the operation of these causes, both sides of the heart, in warm blooded animals, soon lose their power after re- spiration ceases. The arteries, under such cir- cumstances, it is evident, cannot long supply fluids proper for the purposes of secretion, the nervous and muscular solids, therefore, soon de- viate from the state necessary for the functions of life, which at length cease in every part. The above appears to be the order in which the functions always cease in death, whether it be occasioned by injury of the sanguiferous, or nervous systems, or both, with the exception of by the vicinity of the maternal blood of the placenta, although this gives it the florid colour, as may be seen by opening the vessels of the chord, is sufficient for the functions of the per- fect animal. One of these functions, which we have reason to believe from many phenomena, as well as from direct ex- periments, is intimately connected with the change effected on the blood by the air, the evolution of caloric, it is evident, is immediately after birth required to be in a state of much greater activity than in the foetus, which is surrounded by a medium of its own temperature. 228 those cases in which the nervous system is so impressed, as immediately to destroy all the func- tions. The degree of vital energy required for the sensorial, appears to be greater than that required for the nervous and muscular functions, the sensorial functions ahvays, except in the case just mentioned, in which death is instantaneous throughout the system, ceasing first. Respiration, consequently, is the first vital function which fails, being the only one to which the sensorial power is necessary. Bichat has been at great pains to ascertain the effects of black blood on the lungs and other or- gans. To his experiments on this subject I re- fer the reader. There are but few parts of the physiological works of Bichat which can be con- fidently referred to. In general he has allowed his reasonings to go far beyond the evidence af- forded by his observations and experiments. I shall take this opportunity of making a few re- marks relating to the principal points in which I have differed from him. He was unacquainted with the fact, that the spinal marrow performs its functions independently of the brain,* and there- * The independence of the spinal marrow on the brain, as far as relates to its power over the muscle,s of voluntary motion, appears from the experiments of M. le Gallois; and as far as relates to secretion, from experiments laid before the reader in the second section of the seventh chapter of this Inquiry. 229 fore did not see the difficulty respecting respira- tion stated by M. le Gallois, but seems to think that the division of the spinal marrow near the head, occasions death by preventing the nervous influence of the brain from reaching the intercos- tal muscles and diaphragm. The want of this knowledge leads him into inaccuracies, both in his observations on death and other passages; which are increased by his not being aware, that the sensorial and nervous powers have no direct dependence on each other.* He is led into more obvious errors, as far as I am capable of judging, in various parts of his works, particular- ly in those which relate to the passions and the death of the brain, by his not knowing that the heart and blood vessels may be directly influ- enced, and even their power directly destroyed, by agents acting either on the brain or spinal marrow ; and by his supposing that the ganglions are capable of preparing nervous influence inde- pendently of the brain and spinal marrow, a sup- position which we have seen contradicted by many experiments, and which Bichat does not attempt to support by any observation or experiment di- rectly bearing on the point. * It appears, however, from various facts, as I have alrea- dy had occasion to observe, that neither of these classes of functions is confined either to the brain or spinal marrow; both organs partaking of both, although the brain is the chief seat of the sensorial, and the spinal marrow, of the nervous functions. 230 These circumstances have even led him into the most striking inconsistencies in his great di- vision of the functions into organic and animal. If the experiments which have been laid before the reader be correct, the sensorial functions con- stitute the animal, and the nervous and muscular, the organic life. To this, it may be objected, that plants and the less perfect animals have no nervous system. Would it not be more correct to say, that the operation of their nervous system is more confined? Wherever secretion is per- formed, the nervous influence, or a power resem- bling it, must exist. In order that a being pos- sessed of the nervous and muscular systems alone, may live in perfect vigour, it is only necessary, provided it be supplied with food, that respiration should be performed as circulation is, by powers of involuntary motion. A being so formed, though possessed of all the powers of life, would be wholly unconnected with the external world, except by deriving its food and the influence of the air from it; all other intercourse with that Avorld depending on the sensorial power. Such is the life of vegetables, and we have reason to believe, that that of the lowest class of animals differs from it in little else than degree.* An * I do not mean to say that the change effected on the air by plants is of the same nature with that effected by ani- mals, or that they possess a circulation similar to that of 231 animal of this class approaches as nearly, as facts will alloAV us to suppose, to one possessing merely organic life, according to Bichat's defini- tion of it; yet, in the second section of his sixth article, he maintains, that every thing relative to the passions belongs to the organic life; an incon- sistency which alone is sufficient to prove a radi- cal defect in his system. Can the passions belong alone to that life in which they never can be ex- cited, in which they never can operate! Even according to Bichat's definition of organic life, it is common to the animal and vegetable world. No writer, as far as I knoAV, has attempted to explain the folloAving- difficulty respecting the foetal state. The influence of the brain and spi- nal marrow, we have seen, is necessary to the function of secretion, and consequently to the life and growth of the body ; but foetuses have been born alive without either of these organs.* To remove this part of the difficulty it has been said that in such foetuses the nerves perform the func- tions of the brain and spinal marrow. This is not only a gratuitous supposition, but opposed by almost every fact on the subject relating to the animals; but we know that air is necessary to their exist- ence, that some change in it is effected by them, and that in their vessels or canals there is a continual motion of their fluids. * Page 61. 232 perfect animal. If, however, we admit this sup- position, it will go but a very short way toAvards removing the difficulty. How shall we account for the life and growth of the foetus, Avhen the whole nervous system appears an inorganised sub- stance, and, as far as we can see, wholly incapa- ble of its functions ; while the sanguiferous sys- tem appears to be completely organised, and ca- pable of all its functions ? Nay, the heart may be seen performing its functions in the chick in ovo when no vestige of brain or spinal marrow can be traced. What in all these cases supplies the place of nervous influence ? What influence co-operates with the sanguiferous system in ef- fecting the secretions ? Did the evolution of the brain and spinal marrow in the formation of the animal keep pace with that of the sanguiferous system, a difficulty of some Aveight Avould still remain. If the sanguiferous and nervous sys- tems be co-existent, the formation of the animal must begin at more than one point, a supposition contrary to the simplicity observed in the opera- tions of nature. The experiments which have been laid before the reader do not explain these difficulties; but they suggest an explanation of them, the accura- cy of which must be ascertained by further expe- riments. If the nervous influence be galvanism, there may be some apparatus in the uterine sys- tem for collecting and applying this agent, which 233 is every where diffused, till the brain and spinal marrow can perform their functions, and which may continue to supply their place where they ne- ver exist. We have seen that galvanism is ca- pable of performing all the functions of the ner- vous system, properly so called. In combination with the powers of circulation it can, therefore, perform all the functions essential to the life of the perfect animal except respiration, to which, we have seen the sensorial power is necessary. It is worthy of remark, that this is the only function, immediately essential to life in the perfect ani- mal, which does not exist in the foetal state. We have seen that in dying the sensorial pow- ers are the first which cease, their continuance seeming to require the most perfect co-operation of the sanguiferous and nervous powers. For the same reason they appear to be the last which are formed. If the foregoing view of the subject should, on investigation, be found correct, we must regard the rudiment of life as confined to the central part of the circulation, from which, by the power of galvanism, collected by some means external to the foetus, all other parts are gradually evolved, till within the foetus itself a galvanic apparatus of sufficient power for the performance of the ner- vous functions is produced; the sensorial func- tions appearing to be superadded when all the others approach to their perfect state. A difficulty similar to that we have been consi- 32 234 dering, exists respecting the lowest class of ani- mals in which no nervous system can be disco- vered, and vegetables. Both of these classes of beings must necessarily possess the secreting power. It is requisite to the formation and groAVth of their bodies; and Mr. Hunter found that the most imperfect animals are capable of occasioning an evolution of caloric. Is it probable that, in a more advanced state of knowledge, we shall find in these beings means of collecting and applying galvanism ? CHAP. XL A review of the inferences from the preceding experiments and observations. From the various experiments and observa- tions which have been laid before the reader it appears, 1. That the vessels of circulation possess a power capable of supporting a certain motion of the blood independently of the heart. Exp. 24, ^75, 76. 2. That the power both of the heart and ves- sels of circulation is independent of the brain and spinal marrow. Exp. 1, 2, 3, 4,5,6, 7, 8, 9,10, 11,12,13. 3. That the nervous influence is capable of act- 235 ing as a stimulus both to the heart and vessels of circulation. Exp. 14,15,16,17, 18, 23, 26, 27, 28. 4. That the nervous influence is capable of acting as a sedative both to the heart and vessels of circulation, even to such a degree as to destroy their power. Exp. 16,17,18,19, 20, 21, 22, 26, 27, 28, 29, 30. 5. -That the effect of the sedative is not the re- sult of the excess of stimulus, but, like excitement, the direct operation of the agent. See the obser- vations after Exp. 40, and the experiments there referred to.* 6. That the power of the muscles of voluntary motion is independent of the nervous system, and that their relation to this system is of the same nature with that of the heart and vessels of circu- lation, the nervous power influencing them in no other way than other stimuli and sedatives do. Exp. 31, 32, and the observations under Exp. 32. 7. That the cause of the muscles of voluntary and involuntary motion appearing at first view essentially to differ in their nature, is their being excited by stimuli essentially different, the former being always excited by the nervous influence, * A moderate application of every agent appears to act as a stimulus; an excessive application of it, as a sedative. The quantities which act as stimulus and sedative bear no particular proportion to each other, but in different agents exist in every possible proportion. 236 the latter though occasionally excited by this in- fluence in all their usual functions obeying other stimuli. See the observations under Exp. 32. 8. That the brain, and spinal marrow act each of them, directly on the heart as well as on the muscles of voluntary motion. Exp. 18, 19, 23. 9- That the laws which regulate the effects of stimuli applied to the brain and spinal marrow on the heart and muscles of voluntary motidn are different. Exp. 33, 34, 35, 36, 37, 38, 39,40. 10. That mechanical stimuli applied to the brain and spinal marrow are better fitted to ex- cite the muscles of voluntary motion, and che- mical stimuli, the heart. Exp. 33, 34, 35, 36, 37, 38. 11. That neither mechanical nor chemical sti- muli applied to the brain and spinal marrow ex- cite the muscles of voluntary motion, unless they are applied near to the origin of their nerves, and consequently that these muscles are excited by stimuli applied to very minute parts of the above organs. Exp. 33, 35, 37. 12. That both mechanical and chemical sti- muli applied to any considerable part of the brain or spinal marrow increase the action of the heart, which cannot be increased by any stimulus ap- plied to a minute part of these organs. Exp. 34, 36, 38, 41,42, 43. 13. That the heart obeys a much less poAver 237 ful stimulus applied to the brain and spinal mar- row than the muscles of voluntary motion do. Exp. 35, 36, 37, &c. and observations after Exp. 43. 14. That stimuli applied to the brain and spi- nal marrow excite irregular action in the muscles of voluntary motion. Exp. 38, 35, 37- 15. That no stimulus applied to the brain or spinal marrow excites irregular action in the heart or vessels of circulation, nor is their ac- tion rendered irregular by sedatives, unless a blow, which crushes a considerable part of the brain or spinal marrow, be regarded as a seda- tive. Exp. 28, 39, &c. 16. That the excitement of the muscles of vo- luntary motion takes place chiefly at the moment at which the stimulus is applied to the brain and spinal marrow, while that of the heart may ge- nerally be perceived as long as the stimulus is applied. Exp. 40. 17. That after all stimuli applied to the brain and spinal marrow fail to excite the muscles of voluntary motion, both mechanical and chemical stimuli so applied still excite the heart. Exp. 38. 18. That all the foregoing differences in the effects of stimuli applied to the brain and spinal marrow on the heart and muscles of voluntary mo- tion are referable to the following law : That the heart is excited by all stimuli applied to any con- 238 siderable part of the brain or spinal marrow, while the muscles of voluntary motion are only excited by intense stimuli applied to certain small parts of these organs. See the observations un- der Exp. 43. 19. That the function of secretion is destroyed by dividing the nerves of the secreting organs. Exp. 44, 45. 20. That it may be restored after it is thus destroyed by the galvanic influence. Exp. 46,47, 48, 49. 21. That lessening the extent of the nervous system by destroying the influence of any consi- derable part either of the brain or spinal marrow, deranges the secreting power. Exp. 58, 59, 60, 61, 62. 22. That dividing the spinal marrow does not derange the secreting power. Exp. 63. 23. That the vessels of secretion only convey the fluids to be operated upon by the nervous in- fluence. See Chap. 5. Sec. 3, and the experi- ments there referred to. 24. That these vessels, like the vessels of cir- culation, are independent of; but influenced by, the nervous system. Ib. 25. That the peristaltic motion of the stomach and intestines is independent of the nervous sys- tem. Exp. 50, 51. 239 26. That it is capable of being influenced through it. See the beginning of Chap. 7. 27. That in the stomach of the rabbit, and pro- bably in that of similar animals, the food when received into the stomach remains at rest in the central part of this organ, and unmixed with the food previously taken; and that it is changed in proportion as it approaches the surface of the sto- mach, in consequence of that, previously there, being moved on towards the pylorus. Exp. 53, 54, 56. 28. That the food is most mixed with the fluids of the stomach, and the greatest change is effected in it in the cardiac end of the stomach. Exp. 56. 29. That the food is much dryer and of a more uniform consistence, its digestion being further advanced, in the pyloric than in the cardiac end of the stomach. See Exp. 55, and the observa- tions under it. 30. That the efforts to vomit occasioned by the division of the eighth pair of nerves, arise from fresh food coming into contact with the surface of the stomach, no longer covered with its proper fluids. See the observations near the end of the first Section of Chap. 7, and the experiments there referred to. 31. That the muscular power of the stomach remains after the division of the eighth pair of nerves, by which all that part of the food which has undergone the action of the gastric juice is 240 carried into the intestine, undigested food alone remaining in the stomach. Ib. 32. That the secreting power of the stomach is almost as much deranged by destroying a con- siderable part of the spinal marrow, as by diAid- ing the eighth pair of nerves. Exp. 58, 59, 60. 33. That a similar observation applies to the secreting power of the lungs. Exp. 44, 45, 49. 34. That the stomach and lungs, like the san- guiferous system, are influenced by every part of the brain and spinal marrow. Exp. 44, 45, 58, 59, 60, 61, 62. 35. That the destruction of any considerable part of the spinal marrow lessens the tempera- ture of the animal. Exp. 58, 59, 60. 36. That the galvanic influence occasions an evolution of caloric from arterial blood, if it be subjected to this influence as soon as it leaves the vessels. Exp. 64, 65, 66, 67. 37. That the gahanic influence occasions no evolution of caloric from venous blood, although subjected to it as soon as the blood leaves the ves- sels. Exp. 68, 69, 70. 38. That there is no evolution of gaseous fluid from arterial blood on its leaving the vessels. Exp. 71- 39- That, if caloric be admitted to be a sub- stance, its evolution from the blood being effect- ed by the same means by which the secreted fluids 241 are formed, it must be regarded as a secretion. See the observations under Exp. 7fy and page 228. 40. That the division of the spinal marrow does not destroy any of the functions of either half of it, (22) the paralysis of the lower part of the body, occasioned by its division, arising from that part having its communication with the principal source of sensorial power destroyed. See Exp. 63, and the observations on the sensorial power in Chap. 10. 41. That the ganglions are a secondary cen- tre of nervous influence, whose nerves are as ex- tensively distributed as those Avhich proceed from the brain and spinal marrow. See Chap. 9. 42. That the ganglions are the means by which the influence of every part of the brain and spinal marrow is bestowed on the parts, which we have found influenced by every part of these organs. See Chap. 9, and the experiments there refer- red to. 43. That the influence of every part of the brain and spinal marrow is bestowed on all parts directly or indirectly necessary to the due per- formance of secretion, this function requiring the influence of every part of these organs (21). Exp. 44,45, 58, 59, 60, 61, 62. 44k That the position of the ganglions and 33 "242 the distribution of their nerves tend to confirm the view of their use afforded by the above experi- ments. See Chap. 9. 45. That we have reason to believe, that the great sympathetic nerve arises from the spinal marroAV.* Ibid. 46. That the proof of the vessels possessing a principle of motion independent of their elasticity, which bears the same relation to the nervous sys- tem with the excitability of the heart; not only as far as respects the kind of influence which they derive from that system, (43) and the way in * This position does not rest as M. le Gallois maintains on the fact, that crushing any considerable part of the spinal marrow destroys the power of the heart, while the removal of the brain leaves it unimpaired, because the reader has seen that crushing the brain in like manner destroys the power of the heart, which remains uninfluenced by the re- moval of the spinal marrow. It appears to rest on the following circumstances. The sympathetic nerve is largest about the middle of the spine, becoming less as it ascends and descends. We have found from direct experiment that the thoracic and abdominal vis- cera are influenced by every part of the spinal marrow, which can only be through the medium of this nerve, the influence of the brain on the other hand, as appears also from direct experiment, being conveyed to these viscera by the eighth pair of nerves. Bichat found that the effects of dividing the eighth pair of nerves in the neck are not increased by divid- ing in the same place the great sympathetic nerve. See Chap. 9. 243 Avhich it is supplied to them, (42) but also as far as respects the purposes for Avhich it seems to be bestowed on them, (43) affords a strong argument for believing, that this power is of the same nature with that of the heart. See the Experiments re- lated in the two first Chapters of the present part of this Inquiry, also Exp. 39, 44, 45, 58, 59, 60, 61, 62, and Chap. 5, Sec. 3, and Chap. 9. 47« That the various functions of the animal body may be divided into sensorial, nervous, and muscular. See Chap. 10, and the experiments there referred to. 48. That the sensorial power is not wholly confined to the brain, nor the nervous to the spi- nal marrow, both powers in a greater or less de- gree residing in both organs. See Exp. 72, and the observations which precede and follow rt. 49. That the division of the brain into cere- brum and cerebellum seems to relate to the senso- rial functions, since the muscles both of voluntary and involuntary motion appear to bear the same relation to both. Exp. 33, 34, 35, 36. 50. That what we call death is the ceasing of the sensorial poAver alone, the nervous and mus- cular powers still continuing. Exp. 73, 74, 7&> 76, 77, 78, 79, 80, 81, 82, 83, and the observa- tions preceding and folloAving these experiments. 51. That in the function of respiration the sen- sorial, nervous, and muscular powers are com- 244 bined. See the observations after Exp. 83, and the experiments there referred to. 52. That it is owing to the ceasing of respira- tion, that the destruction of the sensorial poAver is followed by that of the nervous and muscular powers. Ibid. 53. That whatever be the cause of death the functions cease in this order, unless the sensorial or nervous system be so impressed as instantly to destroy all the functions. Ibid. Such are the immediate inferences from the ex- periments and observations which have been laid before the reader. By comparing them together we arrive at the following conclusions. The power of the muscles both of voluntary and involuntary motion is independent of the ner- vous system, and arises from the mechanism, of the muscular fibre itself. Both these sets of muscles are equally capable of being excited by the nervous influence, but while this influence is the sole stimulus to which the muscles of volun- tary motion are subjected, it acts only occasionally on the muscles of involuntary motion, which are excited in all their usual actions by stimuli inde- pendent of it, and consequently of the will. When the latter muscles are excited by the ner- vous influence, it is not applied to them in the same way as to the muscles of voluntary motion, to Avhich it is sent directly from the brain and spi- 245 nal marrow, each muscle receiving its nervous in- fluence from a particular part of these organs; while to the muscles of involuntary motion, it is sent through the great chain of ganglions, each muscle receiA7ing its nervous influence from every part of the brain and spinal marrow. The excitement of the muscles of involuntary motion in all their usual functions, appears to be rendered independent of the nervous influence, because these functions require a more uniform excitement than could have been derived from this source; and they appear to be subjected to the influence of the whole brain and spinal mar- row, because they are directly or indirectly sub- servient to the function of secretion, which re- quires for its due performance the influence of every part of these organs; for the nervous in- fluence is not supplied by the brain alone, the spi- nal marrow supplying a necessary part of it, and that independently of any operation of the brain on this organ. In the function of secretion, the sanguiferous system appears only to supply the fluids to be operated upon by the nervous influence; and the evolution of caloric, which supports animal tem- perature, is also effected by the action of this in- fluence on the blood. We have reason to believe that the nervous influence is the galvanic fluid, collected by the 246 brain and spinal marrow, and sent along the nerves ; galvanism being, not only of all artifi- cial means of. exciting the muscles, that which seems best adapted tj this purpose, but capable of both forming the secreted fluids, and causing an evolution of caloric from the blood, after the nervous influence is withdrawn.* The nervous power is not more distinct from the muscular, than it is from the sensorial power. We find the first capable of its functions after the last is withdraAvn. The only function essential to animal life, in which the sensorial power is concerned, is respi- ration, and consequently it is by the interruption of this function that the removal of the sensorial power proves fatal, except where the sensorium is so impressed as immediately to destroy all the functions. The sensorial power appears to be the last which is produced, and the first whose operation ceases. * If such be the facts, we must either admit the identity of the nervous influence and galvanism, or that there is another power capable of the more complicated as well as the more simple functions of the nervous influence, an inference which is surely at variance with all just rules of reasoning. I have, in various parts of the preceding inquiry, had occasion to mention additional arguments in favour of the former opi- nion, (see Page 133, 141, &c.) and in the next chapter the reader will find some facts relating to the human body itself tending to support it. 247 The foregoing conclusions seem to reconcile all the apparent contradictions stated in the first part of this inquiry. The heart continues to act for some time after it is removed from the body, and performs its func- tions in the foetal state when neither the brain nor spinal marroAV has existed; because it has no direct dependence on the nervous system, and is only influenced by the removal of the brain and spinal marrow in the perfect animal, in con- sequence of the failure of respiration.* The heart is supplied Avith nervws, and subject to the influence of the passions, bedause, although independent of the nervous system, it is capable of being influenced through it. Thus, when we remove the brain and spinal marrow, the action of the heart is unimpaired, because it is independent of these organs. When Ave crush them, it is enfeebled or destroyed, be- cause it is influenced through them; and the greater the portion destroyed, and the more sud- den its destruction, the greater injury the heart * It is evident from what has been said, that could we perfectly imitate the function of respiration after the removal of the brain and spinal marrow, the heart would soon begin to feel the effects 6f the general failure of the secreting power; the failure of the secreting power in the lungs, indeed, as I have already had occasion to observe, probably constitutes one of the chief differences between natural and artificial respiration. 246 sustains. These facts reconcile the apparent con- tradictions in the experiments of M. le Gallois. The heart is independent of the Avill, because it is exposed to the constantly renewed action of a stimulus, over which the will has no control; and because there is no act of volition which could be performed through the medium of the heart. » The function of the stomach is (destroyed by withdrawing the influence of the brain or spinal marroAV, while that of the heart is unimpaired, because the function of the heart depends wholly on the muscula*r power, which we have found in every part of the body independent of the nervous influence, while the function of the stomach chiefly depends on the secreting power, which we have found every where dependent on this influence. As far as the function of the stomach is muscular, it also continues after the nervous influence is withdrawn. The digested part of the food is still carried onwards into the intestine. The difficulties stated by M. le Gallois re- specting the function of respiration, seem to dis- appear when it is admitted, that although the muscular and nervous powers, concerned in this function, are, as M. le Gallois states them to be, independent of the brain, the sensorial power is here necessary to call them into action; and that the lungs, being chiefly supplied with nerves from the eighth pair, the sensorial power must, as far 249 as regards them, cease, when that part of the me- dulla oblongata, from which these nerves origi- nate, and to which all impressions communicated through the spinal marrow must also be sent, is destroyed. The powers of respiration remain after decapitation, but the sensation which ex- cites the animal to call them into action is gone. CHAP. XII. On the application of the foregoing experiments and observations to explain the nature and im- prove the treatment of diseases. A considerable length of time alone can shew how far the principles, which seem to be esta- blished by the experiments laid before the reader in the preceding inquiry, may tend to improve the knowledge and treatment of diseases. It is my intention, in the present chapter, to point out in what instances they at first view appear to pro- mote these ends. I shall begin Avith the diseases which arise chiefly from a fault in the sanguife- rous, afterwards making some observations on those whose cause chiefly exists in the nervous system. I use the qualifying words of the pre- ceding sentence, because there is hardly any dis ease of the sanguiferous, whose svmptoms do not 34 250 in some degree depend on the state of the nervous system; and on the other hand, in almost all the diseases of the latter, the sanguiferous system is more or less affected. It is evident, however, from a review of the symptoms of these two sets of diseases, that the nervous more amply partakes of the affections of the sanguiferous system, than the sanguiferous of those of the nervous system. The cause of which is sufficiently evident. We have found that the circulation is immediately necessary to the functions of the brain and spi- nal marrow, but that those of the heart and blood vessels may go on for a certain length of time af- ter the former organs have ceased to exist, having only on these organs an indirect dependence through the functions of respiration and secre- tion.* Of the diseases of the sanguiferous system there are some in which the force of the circulation is diminished, so that the due supply of blood to the brain fails, producing, according to the degree in which this happens, various symptoms of debility or complete syncope; and others, in which the vessels of this organ are distended with more than their due proportion of blood, either in con- sequence of the increased action of the heart and large vessels, or of the vessels of the brain being so * See the experiments related in the first chapter of this part, and chap. 10. 251 far Aveakened that their power of resistance is not in due proportion to the usual vis a tergo. The two last states produce the same train of symp- toms, except that in the former the symptoms of a morbidly increased impetus of the blood through- out the system are more considerable.* The spe- cies of apoplexy depending on these states of the sanguiferous system is very different from that Avhich I shall soon have occasion to speak of, in Avhich the cause originates in the brain itself. These species, we shall find, are frequently com- bined, but when apoplexy, from compression, ex- ists alone, the brain seems to re-act but little on the sanguiferous system. It is observed above, that I found by experiment, that considerable uniform pressure of the brain produces little or no effect on the motions of the heart.f . * I shall not here enter on the' question how far more blood can exist in the encephalon at one time than at ano- ther ; but only observe that, however incompressible the brain, and immoveable the parietes of the head may be, if the brain is compressed by an increased force of circulation, there must then be more blood, however little, in the ence- phalon than when the brain is not compressed; and when we consider how many openings there are in the scull, filled only by soft medullary matter, we may easily perceive why there may exist within the scull very evident accumulations of blood, without corresponding depletion in some other parts of it, the necessity of which certain anatomists have maintained. t Exp, 18. 252 Of Sanguineous Apoplexy. The only change which, in this species of apo- plexy, appears to take place in the action of the heart, is, that it becomes slow and oppressed, as if acting against a stronger Opposing force, and consequently with greater effort than usual. This is easily accounted for by the circulation through the lungs becoming more difficult, owing to the muscles of respiration being less readily called into action in proportion as the insensibility in- creases, and the vessels of the pulmonary system being less powerfully stimulated, in proportion as the blood less perfectly undergoes the change effected by the air. But this is not the only change which takes place in the lungs in apo- plexy. They soon begin to be clogged Avith phlegm, which, in protracted cases, more than the lessened action of the muscles of respiration, at length appears to occasion suffocation. This is readily explained by the experiments which have been laid before the reader, from which it appears, that when a considerable portion of the nervous influence is withdrawn from the lungs, the fluids destined to form their secretions, being no longer properly changed, accumulate in them till the air- cells and bronchial tubes are so clogged that their function is at length wholly destroyed.* Noaa ' Exper. 44, 45. 253 in those cases of apoplexy, in which the brain is so oppressed that the various organs are deprived of a great part of their nervous influence, but not sufficiently oppressed immediately to put a stop to the action of the muscles of respiration, the above change necessarily takes place in the lungs; and as they are of more immediate importance to life than any other organ whose function directly de- pends on the nervous system, this derangement of the lungs is here the cause of death. We see the patient to the last endeavouring to breathe through the phlegm which clogs them and at length produces suffocation. If such be the immediate cause of death in sanguineous apoplexy, we have reason to believe, from experiments* which have been laid before the reader, that by passing a stream of galvan- ism through the lungs they may be enabled to perform their functions for a longer time than Avithout this aid, and thus the life of the patient for a certain time preserved. There is ah evident limit to this effect of galvanism. It is only while the sensibility continues such as to induce the pa- tient to expand his chest to a certain extent and Avith a certain frequency that advantage can arise from it. Whatever be the supply of nervous in- fluence in the lungs, if the air is not admitted Avith sufficient frequency, the proper changes, it is evident, cannot go on. Galvanism, under these * Exper. 46, 47, 48, 49. 254 circumstances, must fail to relieve the breathing, having no other effect but that of a stimulus in promoting the sensorial functions.* On employing galvanism in apoplexy, I had the satisfaction to see the foregoing observations confirmed. After the rattling breathing had come on, and the patient seemed about to be suffocated, he was at least a dozen times made to breathe Avith ease, the accumulation of phlegm gradually disappearing on the application of galvanism, by which his life was evidently prolonged. The inspirations about an hour and an half or two hours before death, becoming very imperfect and less frequent, the galvanism failed to relieve him. The relief obtained, as may be supposed from Avhat has been said, was always of very short duration, the breathing sometimes becoming op- pressed as soon as the galvanism was discon- tinued. I directed it never to be applied for more than ten minutes at a time, and no greater power to "be employed than what I had found a person in health could bear without inconveni- ence. It appears from the experiments which have been laid before the reader, that a long continued and powerful application of galvanism excites inflammation. Its proper use in the case before us will appear from what I shall have oc- casion to say of asthma and suspended animation. * See the observations on the office of the sensorial power in respiration, in chap. 10. 255 It is evident, from the above observations, that the use of galvanism is not suggested as a means of cure in apoplexy; but it will always, I believe, in the species of this disease which we are con- sidering, prolong the patient's life; and may thus, under certain circumstances, by giving more time for the use of those means which tend to remove the cause of the disease, be indirectly the means of saving it. Such are the observations Avhich are suggested by the experiments Avhich have been laid before the reader, respecting the- action of the heart and the state of the breathing in sanguineous apoplexy. The character of this species of apoplexy seems evidently to arise from the poAver of the heart being independent of the brain, so that the action of the former seems to be no otherwise affected by the state of the latter, than necessarily arises from impeded respiration.* These observations, we shall find, by no means apply to all species of apoplexy. With regard to the other symptoms of sangui- neous apoplexy, we have seen it proved by direct experiment, that the loss of power in the limbs does not here arise from any change having taken place in their muscles, whose power seems equally unimpaired! with the muscles ofin voluntary mo- tion; but from the nervous influence, the only * Page 220 & seq. t Exper. 32, and p. 97. 256 stimulus of the former being no longer applied to them. The urine and fasces often pass invo- luntarily, not that any change is produced in the sphincters of the bladder and rectum, but because these being muscles wholly of voluntary motion,* although they still retain that degree of contrac- tion which constitutes their state of rest, when the pressure from within increases, as all stimu- lus supplied to them by the powers of volition is withdrawn, they yield to this pressure. The species of apoplexy which we have been considering, is the most favourable. By the ab- straction of blood the brain is relieved from pres- sure, and its functions are restored, and continue, unless, as frequently happens, especially where the patient has suffered from previous attacks of the disease, the vessels again yield to the vis a tergo.' We thus often see the symptoms relieved by blood letting, but soon recur, and continue to do so till the powers of the constitution are ex- hausted. There are two species of apoplexy, proceeding from the same cause with the disease Ave are con- sidering, but very different both in their nature and prognosis; I mean those in which the dis- tension of the vessels has occasioned rupture, or an effusion of serum. These cases, of a much * Observations similar to those which have been made respecting the muscles of inspiration apply to the sphincters. Page 222 & seq. 257 more fatal tendency, are distinguished from those of mere distension, with great difficulty. The only diagnostics on which) it has appeared to me, we can rely, are, that in the tAvo first cases, particu- larly in the first, the symptoms generally encrease more rapidly than in apoplexy from mere disten- sion, and are little, if at all, relieved by blood letting. That form of serous apoplexy, which is the effect of general debility, and takes place with little or no congestion of the vessels of the brain, may, for the most part, be distinguished by the habit of the patient, and by the tendency, to effu- sion in other parts. To enter further on these cases, and the diagnosis betAveen them and the different forms of hydrencephalus, Avould be fo- reign io my present purpose. I have enumerat- ed them that the reader may the more clearly un- derstand what I mean by nervous apoplexy, on which I shall soon have occasion to make some observations. It will be necessary here to say more of ano- ther affection of the head which insensibly runs into apoplexy from distension. I mean phrenitis. In both we find the vessels of the brain preter- naturally distended, and in many cases can de- tect no other morbid appearance; yet their na- ture must essentially differ. In the one, the pa- tient often resembles a furious maniac, Avhile in- sensibility is always the characteristic of the other. This subject leads me to consider the most impor- 35 258 tant of all the diseases of the sanguiferous system, perhaps I may say, of all the diseases to which Ave are liable. Of Inflammation. I endeavoured many years ago to ascertain the state of the vessels in the various stages of inflam- mation, both in the warm and cold blooded ani- mal, by observing them with the assistance of the microscope. After stating briefly the points which appear to be ascertained by these experiments, a detailed account of which, I have already had oc- casion to observe, is given in the Introduction to the second part of my treatise on Febrile Diseases, I shall endeavour to ascertain from the result of experiments which have been laid before the reader in the preceding Inquiry, what share the nervous system has in producing the symptoms of this disease. In the first experiment on the vessels, the in- flamed web of the foot of a frog was brought be- fore a microscope; and it was observed, that Avhere the inflammation was greatest, the vessels were most distended, and the motion of the blopd was slowest. The distension of the vessels which in the healthy state admit only the colourless part of the blood was apparent, for a much greater number of vessels admitted the red particles in the inflamed than in the souud part, and the in- 259 terstices of the inflamed vessels appeared more opake, either from the enlargement of innumera- ble small vessels, still too small to admit the grosser parts of the blood, or from an effusion of its more colourless parts.* With a view to ex- cite the vessels of the inflamed part, I wetted it Avith spirits, and directed on it the concentrated rays of the sun from the concave reflector of the microscope. In proportion as I succeeded by these means in increasing the velocity of the blood, the diameters of the vessels Avere dimi- nished, their interstices became more transpa- rent, and the appearance of inflammation was in* the same proportion lessened. In the second experiment I observed the in- flammation from its commencement. The. fins and tail of the lampern became inflamed by ex- posure to air. By bringing the former before the microscope, I observed the circulation became more languid and the vessels enlarge as the in- * Dr. Lubbock, and Mr. Allen, without having made any experiments on the subject, and guided merely by the phe- nomena of the disease, maintained, about the year 1790, that inflammation arises from a debility of the vessels of the part. Some hints of this opinion are to be found in writings of an earlier date, but the above gentlemen, in the discussions of the Medical Society of Edinburgh, were the first who brought it forward in a connected form. Neither, as far as I know, has published any thing on the subject; I cannot, therefore, say how far their sentiments, in the detail of the opinion, correspond with mine. 260 !lanimation came on. The motion of the blood in the most inflamed parts at length ceased altogether. By gentle friction and the application of distilled spirits, I repeatedly succeeded in accelerating the motion of the blood in the inflamed parts. In • proportion as this happened, the vessels became paler, and the inflammation was evidently di- minished. These experiments having been made on the cold blooded animal, the mesentery of the rabbit was chosen for the, subject of the next experiment. The result was still the same. As soon as the inflammation began, the vessels began to enlarge, and the motion of the blood became languid; these changes going on till in the most inflamed parts the vessels were enlarged to several times their original diameter, and the motion of the blood ceased altogether. I repeatedly occasioned debility of the capillaries of particular parts of the mesentery by irritating them, and thus saw inflammation rapidly excited by the vis a tergo distending the debilitated vessels. It appears from these experiments that the state of the smaller vessels in an inflamed part is that of preternatural distension and debility. That of the larger vessels may be ascertained Avithout the aid of the microscope. We readily perceive, on viewing an inflamed membrane, that they do not suffer a similar distension, and the increased pul- sation of the arteries sufficiently evinces their in- 261 creased action. In inflammatory affections of the jaw and the head for example, a greatly increas- ed action of the maxillary and temporal arteries is readily perceived by the finger. It is to be ob- served, hoAvever, that, although inflammation, as was evident from the foregoing experiments, begins in the capillaries, if it continues, the circulation in the smallest vessels becoming very languid, those immediately preceding them in the course of circulation begin to be distended and conse- quently debilitated. Thus, when the lampern was first exposed to the air, the inflammation in the fins and tail assumed the appearance of a slight blush, in Avhich it was difficult with the naked eye to discover any vessels; but after some time had elapsed, vessels of a considerable size were seen passing through the inflamed parts. It is evident that this cannot go very far, because when the arteries preceding the capillaries have lost their power, the circulation is no longer in any degree supported in the latter, and gangrene soon ensues. The difference between what is called active and passive inflammation seems to depend on the degree in which the arteries supplying the vis a tergo to the debilitated vessels are excited. In short, inflammation seems to consist in the debility of the capillaries, followed by an increas- ed action of the larger arteries ; and is terminat- ed by resolution, when the capillaries are so far 262 excited, and the"Targer arteries so far Aveakencd by the preternatural action of the latter, that the power of the capillaries is again in due proportion to the vis a tergo. Thus far, I cannot help thinking, the nature of inflammation appears sufficiently evident. The motion of the blood is retarded in the capillaries in consequence of the debility induced on them, an unusual obstacle is thus opposed to its motion in the arteries preceding them in the course of circulation, which are thus excited to increased action. Several difficulties, however, remain, on which the experiments just related throw no light. Why does a failure of power, of small extent in the capillaries of a vital part, strongly excite, not only the larger arteries of the part affected, but those of the whole system; while a more exten- sive debility of the capillaries of an external part excites less increased action in the larger arteries of that part, and often none at all in those of the system in general ? Why does inflammation often move suddenly from one part to another, when we see no cause either increasing the action of the capillaries of the inflamed part or weakening those of the part now affected? Why does in- flammation often arise in parts only sympatheti- cally affected, and consequently far removed from the offending cause? Why is inflammation often as apt to spread to neighbouring parts, betAveen -which and the part first affected there is no cli- 263 rect communication of vessels, as to parts in con- tinuation Avith that part ? These phenomena, it is evident, are referable to the agency of the nervous system, and seem readily explained by the experiments Avhich prove that the effects of both stimuli and sedatives, act- ing through this system, are felt by the vessels, and that, independently of the intervention of any effect produced on the heart.* Thus the irrita- tion of the nerves of the inflamed part may ex- cite the larger arteries of this part, or of distant parts, or of the whole sanguiferous system. It will, of course, be most apt to do so where the irritation excited by the inflammation is greatest, and consequently in the more important vital parts. It cannot appear surprising, that inflam- mation should suddenly cease in one part and at- tack another, when we knoAv that the nerves are capable of exciting to due action the capillaries of the one part, and in the other of impairing the vigour of those which have not yet suffered. In the same way we account for parts only sympa- thetically affected becoming inflamed, and for in- flammation readily spreading to neighbouring parts, Avhich always sympathise, although there is no direct communication betAveen them, either of vessels or nerves. From the foregoing vieAV of inflammation the * Exp. 27, 28. 264 principles on which its treatment is founded are obvious. All the local means are calculated either to lessen the contents of the morbidly distended vessels, or to excite these vessels to expel them. The general means are regulated by the effects produced by the disease on the more distant ves- sels, through the medium of the nervous system ; the objects of this part of the treatment being nei- ther to allow the action of these vessels to fall so low that it is incapable of supporting any degree of circulation in the debilitated vessels, nor to be- come so powerful as further to distend by gorg- ing them with blood. Thus, when the symptoms of active inflammation run high, we lessen the vis a tergo, Avhen gangrene- is threatened, we in- crease it. When the inflammation is of great extent, or in a part of great importance, the Avhole sangui- ferous system appears, in consequence of the impression made on it through the nervous sys- tem, to embrace its contents with greater force than usual, apparently for the purpose of sup- porting the circulation in the debilitated part. Hence appears to arise the hard pulse, from the degree of which we may generally judge of the degree of the inflammation. Mr. Hunter's observations, in his work on in- flammation, as nearly correspond with the fore- going vieAV of this disease, as the unassisted eye and the pre-couceived opinions, which he had, in 265 common with the rest of the medical world, adopt- ed, admit of. " The vessels," he observes,(i both arteries and veins, in.the inflamed part, are en- larged, and the part becomes visibly more vas- cular, from which we should suspect that instead of an increased contraction, there was rather what would appear an increased relaxation of their muscular powers, being, as we might suppose, left to the elasticity entirely. This would be reducing them to a state of paralysis simply, but the power of muscular contraction would seem to give way in inflammation, for they certainly dilate more in inflammation than the extent of the elastic power would allow; and it must also be sup- posed that the elastic power of the artery must be dilated in the same proportion." Thus far the reader would suppose that Mr. Hunter was de- tailing his observations for the purpose of sup- porting the opinion which I have endeavoured to establish. He proceeds, however, with the in- genuity which characterises all his opinions, to an attempt to reconcile the foregoing appearances with the common opinion of the nature of inflam- mation. " The contents of the circulation being thrown out upon such occasions, would, from con- sidering it in those lights, rather confirm us in that opinion, and when we consider the whole of this as a necessary operation of nature, we must suppose it something more than simply a common relaxation ; we must suppose it an action in the 266 parts to produce an increase of size to answer par- ticular purposes, and this I should call the action of dilatation, as we see the uterus increase in size in the time of uterine gestation, as well as the os tincae in the time of labour, the consequence of the preceding actions, and necessary for the com- pletion of those which are to follow."* The reader will perceive that all the facts recorded in the preceding quotation are in favour of the opi- nion I have defended, the explanation alone be- ing in opposition to it. A little before Mr. Hunter observes, te as the vessels become larger and the part becomes more of the colour of tlje blood, it is to be supposed there is more blood in the part, and as the true inflammatory colour is scarlet, or that colour which the blood has when in the arteries, one would from hence conclude, either that the arteries were prin- cipally dilated, or at least, if the veins are equally distended, that the blood undergoes no change in such inflammation in its passage from the arteries into the veins, which I think most probably the case; and this may arise from the quickness of its passage through those vessels." How diffe- rent would have been Mr. Hunter's inferences, if instead of trusting to the unassisted eye, he had viewed the inflamed vessels through the micro- * Mr. Hunter's Treatise on the Blood, Inflammation and Gunshot Wounds, p. 282. 267 scope. He could then have seen the blood mov- ing, and would have found, that instead of its passage being quickened in the inflamed vessels, it is uniformly rendered slower in proportion to the degree of the inflammation, and in the most inflamed parts, stands still altogether. I have, in the part of my treatise on fevers above referred to, shewn from several facts ascertained respecting the colour of the blood, that, within certain limits, the accumulation of this fluid in the debilitated vessels of the inflamed part necessarily causes the blood to retain the florid colour. . It is worth while to observe the difficulty Avhich Mr. Hunter experiences in attempting to explain, on his view of inflammation, the cause of the throbbing pain of an inflamed part, which is evi- dently a necessary consequence of a debilitated and distended state of the smaller, and increased action of the larger vessels. "This pain in- creases," he observes, (i every time the arteries are dilated, whence it would appear that the ar- teries do not contract by their muscular power in their systole, for if they did we might expect a considerable pain in that action, which would be at the full of the pulse. Whether this pain arises from the distension of the artery by the force of the heart, or whether it arises from the action of distension from the force of the artery itself, is not easily determined; we know that diseased 268 muscles give much pain in their contraction, per- haps more than they do when stretched."* Dr. Parry, in his Elements of Pathology and Therapeutics, takes a view of the nature of in- flammation, as far as I know, peculiar to himself. He makes the following observations on the opi- nion of inflammation, which I had endeavoured to support in the treatise just referred to. " Nei- ther will this conclusion be invalidated were it even proved, according to the opinion of Dr. Wil- son, that the velocity of the blood in the vessels of an inflamed part is diminished, unless it be also proved that the velocity is diminished in a greater proportion than the quantity is increased."! Ac- cording to Dr. Parry's view of the nature of in- flammation it consists in an increased momentum of the blood in an inflamed part. I should be happy to consider particularly every step of the ingenious, though, as it appears to me, fallacious train of reasoning, by which he arrives at that conclusion. But as this would lead into a dis- cussion of considerable length, I shall confine my- self to the statement of such facts as appear to be incompatible with it.J As Dr. Parry admits that there is a greater * Page 287. t Vol. 1. p. 84. | Some of the observations which I am about to make were published in the sixth volume of the Medical Repository. 269 quantity of blood in the vessels of an inflamed part than in the same part Avhen souud, he admits that the vessels in inflammation are morbidly dis* tended, the necessary inference from which is that their power is lessened. This inference did not escape Dr. Parry, but he maintains, in the 198th paragraph, that the blood is moved in the capillary vessels not by the power of these ves- sels, but by the impulse it receives from the heart. This opinion it is not difficult to submit to the test of direct experiment. We have seen it as- certained by the assistance of the microscope, both in warm and cold blooded animals, that the motion of the blood in the smaller vessels conti- nues for a long time after what we call death, al- though immediately after it, a ligature be thrown round all the vessels attached to the heart.* Dr. Parry ascribes the continuance of the motion of the blood in the capillaries, in certain experi- ments of Haller, after the aorta had been secured by ligature and removed from the heart, to the contractile power of the larger arteries ; and he has, in a Avork published since that above refer- red to, entitled " An Experimental Inquiry into the Nature, Cause and Varieties of the Arte- rial Pulse, 5fc." made many interesting experi- ments for the purpose of ascertaining the degree of this power. That something must here be as- * Exp. 24, 25, 75, 76. 270 cribed to it, cannot, I think, be denied; but that the motion of the blood in the capillaries chief! \ depends on their OAvn powers, appears from the following facts, which I have ascertained by re- peated experiments. When the power of the capillaries is destroyed, the vis a tergo, even in the living animal, as the reader has seen in the experiments on the state of inflamed vessels, is not capable of propelling the blood through them. As the motion of the blood in the smaller vessels begins to fail, Avhere there is no inflammation, either in the living or in the dead animal, it is observed to stop and go on, to move backwards and forwards in the same vessel and to stop in some vessels of the same part sooner than in others, phenomena which it is evident, could not arise from the contractile poAver of the larger arteries. I have laid before the reader many experiments of a different na- ture, the results of which appear to be wholly in- compatible with the opinion of Dr. Parry, and which seem to me to prove, in the most unequivo- cal manner, that the motion of- the blood in the capillaries neither depends on the impetus given to it by the heart, nor on the contractility of the larger vessels. I Avish the more to insist on this subject because the authority of Dr. Parry has, with many, given a currency to his opinion. Can all contractility of the larger arteries, the greater part of which according to Dr. Parry's experi 271 ments consists in the mere property of elasticity, be destroyed by crushing the brain or spinal mar- roAv? We find, from experiments 29, and 30, that the immediate effects of crushing either, is that of instantly destroying the circulation in the capillaries. In these experiments, it is true, no ligature was throAvn round the vessels attached to the heart, but the result could not arise from loss of poAver in that organ, because the total removal of it, either in the Avarm or cold-blooded animal, produces no such effect. (Exp. 24, 75, 76.) It is an effect altogether analogous to what take« place in the heart itself, from the same cause. (Exp. 20, 21.) When tobacco Avas applied to the brain, the motion of the blood in the capilla- ries was lessened and soon ceased. (Exp. 26, 27-) Can we ascribe this to the diminished ac- tion of the heart? Its total removal, Ave have just seen, produces no such effect. Nobody Avill main- tain that it is to be ascribed to the tobacco, applied to the brain, destroying all contractility in the larger arteries. Is it possible, from these expe- riments, to make any other inference than that the capillaries possess a poAver similar to that of the heart, Avhich is influenced by affections of the nervous system in the same Ay ay ? Page 242 (46). The motion of the blood in the capillaries, after visible death, seems so far from depending on the elasticity of the larger arterie*. that, as far as I 272 am capable of judging, the emptiness of these ar- teries after death, may be shewn to arise from the continued action of the former set of vessels. Dr. Parry found that the larger arteries have their diameter lessened after death, but that it again enlarges, though not to the same extent. I should be inclined to expbin these phenomena, if, indeed, they at all obtain in a sensible degree, except when the artery is exposed to the influ- ence of the air, in a way different from that pro- posed by Dr. Parry. We must suppose, I think, from the facts just mentioned, that the action of the capillaries combines with the contractile power of the larger arteries, in lessening the contents of the latter. As long as these contents are of suf- ficient bulk to stimulate the vessel, it will closely embrace them, and thus as its contents are les- sened, contract beyond the effects of its elasticity; but by the continued action of the capillaries, the bulk of these contents at length becoming too small to stimulate the vessel, it will be relaxed, and thus, by its elastic power, regain a larger diameter. I have already had occasion to make some observations on this subject,* and to remark hoAV readily the continued action of the capilla- ries, after that of the heart has ceased, may lessen the contents of the larger vessels, vessels in di- * Page 210. 273 viding into branches, having the sum of their areas increased. That the emptiness of the arteries after death, for they are sometimes found quite empty, does not arise from their contractile power, as Dr. Parry supposes, appears even from his own very accurate experiments. They do not teach us that the contraction of the arteries after death is sufficient to obliterate their cavities, and no less degree of it, it is evident, can wholly expel their contents. With respect to some other inferences which Dr. Parry makes from his experiments, I think he will admit, that we may be deceived respect- ing the usual action of the arteries, by dividing and making other experiments on them, while exposed to the air, which applies a peculiarly strong stimulus to parts not usually subjected to its action. If the abdomen of a warm blooded animal be opened soon after death, although the usual effect is an increase of the peristaltic motion in those parts of the intestines which are exposed to the air, sometimes they fall into a state of per- manent contraction, and in this state remain mo- tionless. May not such a permanent contraction, existing in so small a degree as to escape obser- vation, be the cause of Dr. Parry's not having observed any alternate contraction and dilatation in the exposed arteries? Arteries are often very evidently lessened in diameter, and sometimes 37 274 thrown into strong partial contractions by expo- sure to the air.* It must however, be admitted, I think, that the pulse is chieflyf caused in the way Dr. Parry has so well explained. The beatings of the arteries of rabbits, observed in my experiments, were probably of the same na- ture with the motion of the arteries corresponding to the contractions of the ventricle observed by * See Dr. Parry's 13th, 24th, and 26th experiments, and the account of an experiment of Vershuir in Dr. Fowler's Thesis on Inflammation. I have frequently observed a ge- neral lessening of an artery on its exposure to the air. t The word chiefly, as here used, seems to require some explanation. All admit that the arteries are elastic tubes, and it will not be denied that the larger arteries are exposed to a more powerful distending force during the systole than during the diastole of the heart. It necessarily follows, therefore, that these arteries are more distended during the former than during the latter, even on the supposition that the increased stimulus of distension excites no vital action in them. Whether the increased distension is in such a degree as to be sensible, is another question. The experi- ments of Dr. Parry prove that it is not sensible to the eye \yhen the artery is exposed. That it is sensible to the touch appears, I think, from the circumstance, that when the cir- culation is vigorous, the pulse is sensible to pressure too slight to influence the calibre of the artery. It is sensible to the slightest touch: but that the sensation produced in the finger in feeling the pulse, is excited chiefly in the way Dr. Parry has explained, appears from its increasing with the pressure until the latter becomes such as nearly to obli- terate the cavity of the artery. 275 Dr. Parry. This motion of arteries may often be seen in the human body, in the wrists, the temples, and the neck, while the skin is entire. When we consider attentively the results of the various experiments to which I have refer- red, does it not seem a necessary inference, that the blood is moved in the capillaries by the power of these vessels themselves; and, consequently, that if they are debilitated, the momentum of the whole blood in the part, as Avell as its velocity, must be less than in health ? The truth of this in- ference appears, indeed, from direct experiments; for from those made with a view to ascertain the state of the vessels in an inflamed part, of which an account has been given, it clearly appears, not only that the velocity of every part of the blood was lessened, which Dr. Parry admits may be the case, supposing the lessened momentum, aris- ing from this cause, more than compensated by the increased quantity of blood, but that the ge- neral momentum of the blood also in the inflamed part was lessened; because the blood was ob- served to move more and more slowly, till in the most inflamed parts it ceased to move altogether. Now before the momentum of the blood in those parts was wholly lost, it must have passed through all the degrees between the healthy momentum and none; during Avhich the part exhibited the phenomena of inflammation. In the introduction above referred to, I have 276 pointed out in detail, that the view of inflamma- tion there taken is supported by the various phe- nomena of that disease. We may easily, I think, from what has been said, perceive the steps by which inflammation terminates in resolution and in gangrene. In the one case the debilitated capillaries are excited to due action by the increased action of the larger arteries ; in the other the increased stimulus fail- ing to produce this effect, the capillarie's wholly lose their power, and the part becomes subject to the laws of dead matter. The process of sup- puration is more complicated, and between the in- ferences from the experiments which have been related respecting the state of the vessels in an inflamed part, and those afforded by the experi- ments of Mr. now Sir Everard Home,* on the, formation of pus, related in his valuable Treatise on this fluid, there is a chasm, which must be filled up by future observation. It appears from what has been said, compared with the experiments of Sir Everard Home, that when the capillary ves- sels of a part remain for a certain length of time in a state of debility and distension, it often be- gins to secrete a fluid which becomes pus; for Sir * A Treatise on the properties of Pus, by Everard Home, Esq. 4to. London, 1788. This Treatise was republished in 1797, in his work on Ulcere 277 Everard has shewn that this fluid has not the purulent appearance when first secreted, but ac- quires it while it remains on the inflamed surface, and does not acquire it the less readily when re- moved from that surface in a colourless state, pro- vided its proper temperature be preserved, and it is equally exposed to the influence of the .air, which promotes the change. He has, in the above publication, thrown great light on the pa- thology of some of the most important internal dis- eases, by showing how readily pus is formed by secreting surfaces independently of any breach of substance. He found it completely formed by causes of irritation applied to such surfaces in the short space of five hours. Whether this fluid is secreted from the contents of the original vessels, or, as Mr. Hunter supposes, of a new set of vessels formed in the diseased part, we cannot tell. We are also unacquainted with the nature of the pro- cess by which the diseased parts are removed in the formation of abscess. We know not whether it be by an increased action of the absorbents of the part, or by the action of vessels formed for the purpose. We cannot suppose that the diseased parts are melted down and assimilated into its own nature by the action of pus, an opinion at one time prevalent, since we find that this fluid with all its properties may be formed by inflamed surfaces, without any loss of substance taking place, and it more directly appears from the ex- 278 periments of Sir Everard Home, that it does not possess the property of eroding the solids. These topics open a fruitful and interesting field of in- quiry. By patient observation, and the aid of glasses, it is not improbable, in the present im- proved state of chemistry, that the whole process of suppuration might be unfolded. When the larger vessels of a part are debili- tated and consequently distended without previous distension of the capillaries; the disease, which may be termed congestion or partial plethora, is of a nature very different from inflammation. In this case there is little or no distension of the ca- pillaries, as appears from their being pale or only slightly turgid with red blood. The vis a tergo, from the debilitated state of the larger vessels, being too weak greatly to distend them, they more or less perfectly retain their power, and as long as the larger vessels can afford any supply of blood, preserve the circulation, as it appears from what has just been said, they are capable of do- ing both in the warm and cold blooded animal, long after the effect of the powers of the larger vessels has ceased. Such appears to be the state of the vessels of the brain in sanguineous apo- plexy, while in phrenitis the larger vessels are comparatively little distended, the distension be- ing chiefly in the capillaries. This difference is evident on dissection. After the latter disease, Avhen it has been distinctly formed, a general blush 279 is observed in the parts of the brain affected; while, after the former, a preternatural distension of the larger vessels is conspicuous, while the brain itself is often nearly or altogether of the natural colour. It is an observation of writers on phre- nitis, that if coma supervene on delirium in this disease, it is almost always fatal. The cause of which is evident from what has been said. If, while the capillaries are debilitated, the larger vessels, to a considerable degree, also lose tBeir power, the circulation in the former must wholly fail. In other parts, as Avell as in the brain, we con- stantly observe, that the distension of the capilla- ries is attended with acute symptoms, great pain and fever, while that of the larger vessels is ge- nerally attended with little of either, being chiefly denoted by a failure in the function of the part af- fected. The cause of this difference appears from those experiments which prove that the sanguife- rous and nervous systems sympathise in their ex- treme parts in a way they are not found to do in any other ;* which we have reason to believe arises from the capillaries supplying to the nervous in- fluence the fluids on which it operates in the func- tion of secretion,! the failure of which must ne- cessarily occasion a degree of derangement in the * Exper. 44,45. t Chap. 5. Sect. 5. 280 nervous system, which cannot arise to the same degree from causes chiefly affecting the larger ves- sels ; for, however debilitated these vessels may be, unless the circulation in them fail altogether, in which case the death of the part soon ensues, the capillaries, as appears from what has just been said, are still capable of affording a supply of fluids to the secreting power. It is probably, also, from the copious supply of nervous influence sent to fhe capillaries for the purpose of secretion, that these vessels appear to be so much more sensible than the larger vessels. It has long been observed by physiciaus that the inflammation of the same organ sometimes excites acute pain and a great degree of fever, and in other cases comparatively little of these symptoms, being chiefly remarkable by the lesion of function it oc- casions. Thus, inflammation of the brain has been divided into two species—phrenitis and phrenis- mus; the latter differing in no essential respect from sangnineous apoplexy—that of the lungs into pleurisy and peripneumony, &c. The difference of the symptoms in such cases has been explain- ed by the supposition that, in the acute cases, the membrane is affected, and in those less acute the paranchima. Numerous dissections have now proved the fallacy of this explanation. The pa- ranchima alone having often been found affected in the most acute, and the membranes alone in the 281 least acute cases.* I believe it will often appear that in the former the capillaries, in the latter the larger vessels, are the chief seat of the disease. I am aware that this will not always be found to be the case, for the capillaries sometimes suffer distension with little or no pain, particularly where the progress of the disease is slow. In general, however, in proportion as the distension is con- fined to the larger vessels there is less fever and less pain, and when they alone are affected there is little or none of either. * If the reader will consult the 20th Epistle of Morgagni, De sedibus et Causis Morborum, particularly the 9th, 33d, 35th, 39th, 41st, 43d, 47th, 49th and 62d sections of it, and some parts of his 21st Epistle, he will find that the symptoms regarded as peculiar to pleurisy have frequently attended the paranchymatous inflammation of the lungs, and that, when the pleura was not at all affected. When we inspect the bodies of those who die of inflammation of the lungs (says Schroeder, Opusc. Med.) they alone are sometimes found in- flamed, although the symptoms of pleurisy had been well marked. Petrus Servius opened three hundred people at Rome, who died with the symptoms of pleurisy, in which the lungs were greatly inflamed, the pleura little or not at all. Tissot met with similar cases ; and Diemerbroech says, that in two or three cases, in which there had been no acute pain, and where consequently, according to the common opinion, the paranchyma of the lungs alone should have been found affected, the pleura equally partook of the disease. Burse- rius, observes, that dissections are not wanting to prove that inflammation of the pleura has been present without any pain. Sydenham seems to go so far as to believe the paranchyma of the lungs to be very frequently the seat of pleurisy. And 38 282 All local diseases producing fever, seem to con- sist in debility of the capillary vessels of the part affected. Dr. Cullen arranges them all under three heads, Inflammation. Hemorrhagy and Pro- fluvium. If we examine the symptoms of the two last we shall find, that except these diseases are of a mere passive nature, arising from external violence or extreme relaxation, in which cases they do not excite fever, their symptoms are those of inflammation relieved by discharge; in the one case, the effect of rupture of the vessels, in the other, apparently of distension of their extremi- ties ; and it is particularly to be remarked, that it is only in proportion as the symptoms of in- flammation prevail, that those of fever attend. It seems then from direct experiment to be a law Juncker, in his Conspectus Pathologise, observes, that pleu- risy often passes into peripneumony, by which we may un- derstand that the paranchyma was found inflamed where the symptoms had been those of pleurisy 5 for such was the pre- judice in favour of this division of pneumonia, that when it was found that the appearances on dissection did not cor- respond with it, it has been supposed that the one form of the disease had passed into the other, an opinion which seems to have been sanctioned even by Haller. Yet we find in some of the oldest writers more correct observations. Hippocrates speaks of pleurisy and peripneumony as affections of nearly if not altogether, the same parts; and Galen observes that the pain in peripneumony is sometimes acute. Many observa- tions to the same effect might be added from authors of equal authority, both with respect to the disease we are speaking of, and inflammatory affections of other organs. 283 of the animal economy, that debility of the capil- lary vessels, and this alone of all local affections, applies to the nervous system, such an irritation as excites to preternatural action the larger ves- sels of the part, and when of great extent or in vital parts, the whole sanguiferous system. Do these observations throw any light on the nature of fever properly so called ? In this dis- ease we find a general debility of the capillaries followed by an increased action of the heart and larger vessels, its symptoms subsiding as soon as the capillaries are excited to the due performance of their functions. In such a state of the sangui- ferous system, it is evident, that debilitating causes, acting partially, will readily increase the debility of the capillaries affected by them, and thus, as appears from what has been said, excite inflammation, Avhich will either run its usual course or be relieved by hemorrhagy or proflu- vium. May we not thus account for the frequency of these affections in fever? In this disease, inflammation is particularly apt to arise in the brain, because the blood being re- turned thence, by membraneous canals, which cannot partake of the increased excitement of the central parts of the sanguiferous system,* this ex- * The final cause of this structure appears to be to supply a "reater temporary vigour on various occasions where the rapidity of the circulation is increased, particularly where 284 citement necessarily tends to occasion accumula- tion of blood there. Inflammation is also apt to occur in fever in those parts where the vessels are most numerous and delicate, and where they are exposed to any species of injury ; that is, where they are most apt to be debilitated. According to this view of the subject, fever must be regarded as a state of general inflamma- tion, the symptoms peculiar to inflammation not appearing in any great degree, only because the increased vis a tergo, being so much smaller in proportion to the number of, and consequently the resistance opposed by, the debilitated vessels, than in inflammation where the vessels of only one part are debilitated, that it cannot greatly distend them, and consequently, excite the more prominent symptoms of inflammation, unless they become particularly debilitated in some one part; but it often excites all these symptoms in a less degree, increase of heat, redness and fullness of the various surfaces. I may observe also, that in proportion as these symptoms appear the pulse be- comes hard as in inflammation, and the buffy coat shews itself on the blood. Are not all the other symptoms of fever equally the consequences of great efforts are made, and consequently great excitement re- quired in the muscles of voluntary motion ; all organs be- ing, within certain limits, more or less vigorous according to the quantity of blood circulating in them. 285 this state of the circulation, the symptoms of ex- citement arising from the general ehort of the san- guiferous system to excite the capillaries, those of debility from the state of the latter vessels, and the consequences of the ineffectual or but partially successful efforts to restore their due action ? It is evident from what has been said, that the ner- vous is, equally with the sanguiferous system, engaged in these efforts. In what may be called the local treatment of fever we find, that causes exciting the capillaries of any considerable part with which others sym- pathise, the sudden application of cold to the sur- face, the effect of cathartics in the alimentary ca- nal, &c. tend to relieve this disease. With respect to the general treatment, as the whole of the capillaries are debilitated, and the increased vis a tergo consequently bears a less proportion to the resisting force than in inflam- mation, it requires less reduction; but as even here it is apt to exceed the limits most favour- able to the excitement of the capillaries, it must generally be reduced; and in proportion as we reduce it, we find, analogous to what happens in an inflamed part, that the redness, heat, and ful- ness of the various surfaces are relieved. It is equally necessary, however, both in fever and in- flammation, to be careful that we do not so far re- duce the vis a tergo that it can no longer support any degree of circulation in the debilitated capil- 286 laries; in which case we should have general sphacelus in fever, as we have local sphacelus in inflammation, were it possible that any of the functions of life could go on after all the capilla- ries had lost their power. In extreme cases of typhus we see a state approaching to this. If the foregoing observations be correct, the treatment of fever is founded on the same princi- ples with that of inflammation, except, that as the resisting power is greater in fever, less vigorous means of reducing the vis a tergo are proper in the early stage of this disease, and in the latter stage, the means which support it are more fre- quently called for. The attention of Mr. Knight, whose discoveries in the vegetable world, have placed him in the first rank of philosophers, has been peculiarly at- tracted by the galvanic experiments which have been laid before the reader; and the strong ana- logy which subsists between animal and vegeta- ble life, has induced him to reflect much on their results. He has favoured me with many inge- nious suggestions relating chiefly to vegetable life, which Avill be submitted to the test of experiment. One relating to the subject before us, I cannot avoid mentioning, although I have not yet had an opportunity of attempting to profit by it. I mean the use of galvanism in the worst cases of ■typhus, in which there is an universal failure of the secreting power and the debility of the ner- 287 vous system forms so prominent a feature. It may certainly be used with safety, and probably with advantage in this disease. The circum- stance which appears to me to render it doubtful how far it may prove useful in typhus is, that here the due supply of fluids, as well as of ner- vous influence, fails. In restoring the former, galvanism can have no effect different from that of other stimuli. The proper mode of using it, I conceive to be, by many wires from one end of the trough applied to various parts of the head and spine, and many from the other end applied to such parts of the surface as shall send the influ- ence through the body as much as possible in the direction of the nerves. Many of the observa- tions which I shall have occasion to make on the use of galvanism in asthma, and which have been confirmed by repeated trials, will probably be found applicable to this and other cases in which it may be employed. Having taken a cursory view of the nature of the diseases which arise from morbid distension, and consequent failure of circulation in the ca- pillaries and larger vessels of the brain, Ave are now to consider the effects of a deranged state of this organ itself, and how far the experiments which have been laid before the reader throw light on the symptoms arising from this cause. 288 Of Nervous Apoplexy. It is still one of the great desiderata in medi- cine to discover a diagnosis between sanguineous and nervous apoplexy. The objects of the fol- lowing observations are, to trace, as far as I can, with the aid of the experiments which have been laid before the reader, the distinguishing symp- toms of nervous apoplexy, and to ascertain the circumstances which render the diagnostic be- tween this disease and sanguineous apoplexy so difficult. This difficulty is much to be lamented, as there is no instance in which a diagnostic is more necessary, these diseases often proving quickly fatal, and requiring very different plans of treatment. In considering this subject, I shall in the first place point out what appears, from the principles which seem to be established by the experiments related in the preceding Inquiry, to be the neces- sary consequences of great injury of the brain ; ►and then compare these consequences Avith the symptoms which actually attend diseased states of this organ in the human body. As it appears, as far as I am capable of judg- ing, from what has been said, that the leading features of sanguineous apoplexy depend on the fact, that the power of the heart and blood vessels is independent of the nervous system, in conse- 289 quence of which the power of the brain may be overwhelmed by a compressing force, without directly affecting the powers of circulation ;* so I think it will appear from what I am about to say, that the leading features of nervous apo- plexy depend on the fact, that the power of the heart and blood vessels, though independent of the nervous system, may be influenced even to its total destruction through this system.f Let us consider the consequence of such an im- pression made on the nervous system as greatly lessens the power of the heart and blood vessels. We have seen that agents acting on the brain and spinal marrow increase the action of the heart and blood vessels, unless they are of a sedative qua- lity, or applied in excess, that is, in such a degree as suddenly to injure the mechanism of the brain and spinal marrow, they then directly impair the powers of circulation .J If the mechanism of the brain be suddenly destroyed, instant death of all the functions ensues. § The cause applied, how- ever, is rarely sufficient to produce this effect. It generally debilitates without destroying the various functions; the sensibility is impaired; * Exp. 18. f Compare the Experiments related in Chap. I. of this Part, with Exps. 19, 20, 21, 22, 26, 27, 29, 30. \ See the Experiments related in the second Chapter of this part. $Exp. 20, 21. .39 290 the heart acts more frequently and feebly, and, for the most part, irregularly; and the circulating system suffers a similar loss of power in every part of the body. This state is succeeded by some improvement in the symptoms, the heart and blood vessels in some degree recover from the shock they received.* The former begins to beat with less frequency and with more force and regularity, and the latter to convey the blood with greater velocity and in a more uniform stream, f In proportion as this change takes place, the various functions, as I have very frequently ob- served in rabbits, improve, the animal recovering a greater degree of sensibility. If the offending cause has been slight, the symptoms continue to improve; if severe, the heart soon begins again to beat more languidly, and with it all the func- tions gradually fail. If the injury done to the nervous system is of such a nature as particular- ly to debilitate the vessels of the injured part, during that interval, in which the vigour of the circulation is in some degree restored, the vessels of this part must yield to the vis a tergo and the symptoms of inflammation are thus added to those -arising from the original injury. Such appears from the result of the experiments detailed in the preceding Inquiry, to be the con- * Exp. 19, 29. t Ibid. 291 sequences of such an injury of the brain and spi- nal marrow as materially deranges their me- chanism. The reader will perceive that if the foregoing view of the subject be correct, the ner- vous is a much more complicated disease than the sanguineous apoplexy. In the latter, the powers of the nervous system are oppressed, but those of the sanguiferous system are, in the commence- ment of the disease, entire, and only become af- fected through the failure of the functions of respi- ration and secretion. In nervous apoplexy the poAvers of circulation not only suffer directly from the injury done to the nervous system, thus pro- ducing a combination of diseased states of both systems, but the debility of the heart and blood vessels have a secondary effect on the nervous system. The action of the brain and spinal mar- row fail from defective circulation, and a state of these organs, analogous to that which takes place in syncope, is superadded to that produced by the cause of the disease. It is not surprising, therefore, that this species of apoplexy sometimes proves instantly fatal; which sanguineous apo- plexy, affecting the powers of circulation only, through the failure of other functions, never does. The principles of the treatment in the former case also, are much more complicated. In san- guineous apoplexy, we have but one object in vieAV, to relieve the brain from pressure. In nervous apoplexy, while we endeavour to coun- 292 teract the effects of the offending cause on the brain, it is necessary to support the circulation; the failure of which to a certain degree must im- mediately prove fatal. This ought to be done, however, in such a way as tends least to occa- sion morbid distension of the vessels of the head, to which the cause of the disease often renders them liable, and which will produce either san- guineous apoplexy or phrenitis, according as the distension takes place in the larger or smaller vessels. From this view of the subject Ave may readily understand why abstraction of blood often proves fatal in nervous apoplexy, and yet much stimulus cannot be borne. The simplest cases of nervous apoplexy, and those most nearly approaching to the state of the animals in the above experiments, are cases from mechanical injury of the brain. When a blow on the head fractures the scull and occasions part of the bone to press on the brain without doing fur- ther injury to this organ, the case resembles in its nature the sanguineous apoplexy. When the compressing power is removed, the apoplectic symptoms disappear; but when the blow has produced what surgeons call concussion of the brain, the case is only a slighter degree of the state in which the rabbits and frogs were found after the brain had been crushed. No writer, perhaps, has detailed the symptoms of concussion of the brain with greater correctness 293 than Mr. Abernethy, in the third part of his Sur- gical and Physiological Essays. It is impossible not to remark how accurately his account of these symptoms corresponds with the results of the experiments which have been laid before the reader:—«. The Avhole train of symptoms," he observes, ({ following a concussion of the brain, may, I think, be properly divided into three stages. The first is, that state of insensibility and derangement of the bodily powers which im- mediately succeed the accident. While it lasts, the patient scarcely feels any injury that may be inflicted on him; his breathing is difficult, but in general without stertor; his pulse intermitting, and his extremities cold. But such a state can- not last long; it goes off gradually, and is suc- ceeded by another, which I consider as the second stage of concussion. In this, the pulse and respi- ration become better, and, though not regularly performed, are sufficient to maintain life, and to diffuse warmth over the extreme parts of the body. The feeling of the patient is now so far restored that he is sensible if his skin is pricked, but he lies stupid and inattentive to slight exter- nal impressions. As the effects of concussion diminish, he becomes capable of replying to ques- tions put to him in a loud tone of voice, especially when they refer to his chief suffering at the time, as pain in the head, &c.; otherwise he answers incoherently, and as if his attention was occupied 294 by something else. As long as the stupor re- mains, the inflammation of the brain seems to be moderate, but as the former abates, the latter seldom fails to increase; and this constitutes the third stage which is the most important of the se- ries of effects proceeding from concussion. These several stages vary considerably in their degree and duration, but more or less of each will be found to take place in every instance where the brain has been violently shaken." Page 59, 60. In the 67th page Mr. Abernethy observes—" It has hitherto been considered as a desirable object to point out any marks by which we might dis- tinguish betAveen compression and concussion of the brain, but I believe no such criteria have yet been communicated to the public. I think, how- ever, that these diseases may be distinguished. As far as my observation goes, the insensibility is much less in concussion, especially after a short time has elapsed. Patients, in this case, though they seem reluctant to answer questions, yet com- plain much if their heads are moved, and in those instances where it was judged necessary to in- spect the bone, I have generally found that they made great complaint during the operation. The pupils also are usually more contracted than in compression of the brain, the muscles of the limbs retain their natural state of tone, and respiration is performed with little or no stertor, though the pulse generally intermits in a very considerable 295 degree. In the slighter cases of concussion the sickness of the patient is often very great.- But in cases of compression of the brain circumstances very much the reverse of those just related take place. The sensibility is much diminished in proportion to the degrea of the injury. From this cause also the pupils are dilated and the limbs relaxed. The respiration is attended with stertor, and the pulse, as far as my observation extends, is subject to much less intermission." It is evident that in accidents we cannot always expect to find the symptoms of compression and concussion so distinct as in experiments made for the purpose of exhibiting those symptoms; many accidents tending at the same time to produce a greater or less degree of both affections. The chief difference between the symptoms of concussion and nervous apoplexy arising from in- ternal causes is, that in the latter there is not so uniform a tendency to inflammation, which in the cases referred to by Mr. Abernethy is evidently the effect of the injury done to the vessels by the blow, which we have reason to believe causes them to suffer morbid distension as soon as a cer- tain vigour of circulation is restored. It is this renewed vigour of circulation after the immediate effect of the blow has subsided, so remarkable in the experiments just referred to, that again gives some energy to the brain, and explains Mr. Aber- 296 nethy's observation, that the stupor abates as the tendency to inflammation comes on. In nervous apoplexy, from internal causes, the sensibility is often as much impaired as in the sanguineous apoplexy. When this is the case the danger is very urgent; but it frequently is much less so, compared with the severity of the other symptoms and the degree of danger, than in the latter species of the disease; because here the sanguiferous, as well as the nervous system, suffers. In the former case, the derangement of function being confined to the nervous system, the danger is nearly proportioned to the degree of insensibility; but in the case before us, symp- toms of the greatest danger often occur, although the patient is not wholly insensible, and not un- frequently while he is affected with a degree of irritability. The state of the pulse affords the best diagnostic between these species of apoplexy. In the sanguineous, we have seen, it is strong, regular, and generally less frequent than natural; in the nervous, it is weak, frequent, irregular, and sometimes fluttering. Such are the symptoms of distinctly formed sanguineous and nervous apoplexy. Were these diseases always so formed, no attentive practi- tioner could be at a loss to distinguish them. But we have to lament that this is by no means the case, as indeed from what has been said we might 297 a priori have supposed. For it must often hap* pen in apoplexy from distension of the. vessels, that the brain will sustain some further injury than that of mere uniform compression. It is not improbable that the circumstance of the compres- sing force acting partially, may sometimes alone be sufficient to produce this effect; and powerful causes, injuring the mechanism of the brain, must often be of such a nature as at the same time to occasion debility, and consequently more or less distension of its vessels. To these circumstances, and to the difficulty of distinguishing apoplexy arising from mere distension of the vessels, from that arising from an extravasation of blood or serum, it appears to me that all the difficulties of the prognosis and diagnosis of the different spe- cies of this disease are to be ascribed. It is the tendency to distension of the vessels of the encephalon that renders a very stimulating plan of treatment a doubtful practice, even in the most decided cases of nervous apoplexy. Were it not for this, the state of the sanguiferous and nervous systems in these cases equally calls for such a plan. But it would seem that the more debilitated the brain is, the more readily it feels the effects of any morbid distension of its vessels. Thus our practice in such cases is confined on all hands. Irreparable injury may be done by the free use either of stimuli or evacuauts. The mode of treatment which has appeared to me the 40 298 most successful, is a gently stimulating plan com- bined, for the purpose of preventing congestion of the head, with medicines moderately determin- ing to the surface, and keeping the bowels free without occasioning a great discharge from them; with occasional abstractions of blood from the head, when the insensibility seems inclined to in- crease. Profuse sweating not relieving the symp- toms, which is a frequent occurrence in severe cases of nervous apoplexy, seems always to indi- cate great danger, and to arise from a general re- laxation of the extreme vessels. In cases arising from injuries of the head, Mr. Abernethy thinks the great tendency to inflammation altogether for- bids the stimulating plan. I have already pointed out the circumstance which often makes the indi- cations of cure in this respect different in concus- sion of the brain and nervous apoplexy arising from internal causes. The foregoing view of the nature of the diffe- rent species of apoplexy, not the result of precon- ceived opinions, but of facts open to the exami- nation of every one who chooses to repeat the ex- periments, and so strikingly confirmed by the ob- servations of Mr. Abernethy and other writers on the effects of injuries of the brain, may tend per- haps to render the practice in this varied disease more determinate. It seems, by affording a more correct view of the ratio symptomatum of the san- guineous and nervous apoplexy, than could be ob- 299 lained without a knowledge of the relation which subsists between the sanguiferous and nervous systems, to point out with more precision than has yet been done, the symptoms essential to each, and consequently the modes of practice suited to the various cases in which they occur separately, or are blended together. I have entered no fur- flier on these modes of practice than Avas necessary to point out the general principles on which they seem to be founded. Of Affections of the Spinal Marrow. The experiments in which different portions of the spinal marrow were destroyed* seem to throw considerable light on the nature of the symptoms occasioned by diseases of this organ. We have seen that the destruction of any part of it not only renders paralytic, that is, deprives of their only stimulus, the muscles of voluntary motion which correspond to that part, and to all parts of the spi- nal marrow lying below it; but, by lessening the supply of nervous influence to the great chain of ganglions, influences the state of the thoracic and abdominal viscera and the temperature of the ani- mal.f In estimating the effect on the thoracic * Exp. 58, 59, 60. t It appears from what has been said, that although both the muscles corresponding to the part of the spinal marrow 300 and abdominal viscera of destroying portions of the spinal marrow, we must trust rather to the appearances observed in the lungs and stomach after death than to the symptoms produced, be- cause, as the animal can give no account of its feel- ings, no symptom of deranged digestion appears till it goes so far as to produce efforts to vomit, nor of oppressed breathing till it goes so far as to produce evident dyspncea. Thus, in the expe- riments just referred to, it appeared on dissection, that the process of digestion was sometimes wholly suspended, and the lungs more or less congested, where no symptoms of indigestion, and little or no change in the breathing, had been observed. We often complain of affections of the stomach and lungs long before their symptoms can be per- ceived by others. Congestion and even inflam- mation of the lungs do not excite cough in the rabbit. Even in early stages of diseased spine, affec- tions of the stomach and lungs frequently attend, and the patient often complains of a sense of cold. Mr. Pott remarks of this disease, " loss of appe- tite, a hard dry cough, laborious respiration, &c. appear pretty early, and in such a manner as to destroyed, and those corresponding to all parts below it, equally cease to move, it is from different causes; the former because their nervous influence is destroyed ; the latter be- cause their nervous influence is no longer subject to the sen- sorium'. 301 demand attention." And in another place he ob- serves, that there is " an unusual sense of cold- ness of the thighs, not accountable for from the weather." Similar observations are made by every writer on diseased spine. From Avhat I shall have occasion to say of asthma and dyspepsia the reader will see reason to believe that the forego- ing symptoms may probably be relieved from time to time by the use of galvanism. It appears from experiment 63, in which the spi- nal marrow was simply divided, compared with experiments 58, 59, 60, in which portions of it were destroyed, that we may judge of the extent of the injury done to this organ, in diseases of the spine, by the state of the stomach and lungs. Any thing, Avhich so affects the spinal marrow as to interrupt the communication between the brain and other parts, will of course prevent the influence of the will reaching them, however small a part of the spinal marrow may be injured. But if a considerable part of it is so, along with loss of power in the limbs, the patient will expe- rience symptoms of dyspepsia and oppressed breathing proportioned to the importance and ex- tent of the part whose function is destroyed. I have already had occasion to explain Avhy the lungs are particularly affected by the destruction of the dorsal, and the intestines by that of the lum- bar portion of the spinal marrow.* * Page 188 et. seq. 302 The experiments related in the preceding in- quiry seem to point out more precisely than for- mer observations have done, what we are to ex- pect from the use of galvanism in the cure of dis- ease ; and I think it will appear from what I am about to say, that to the want of discrimination in its employment we must ascribe the little ad- vantage which medicine has hitherto derived from the discovery of this influence.* It seems to be an inference from my own ex- periments and observations^ as well as those of others, particularly of M. le Gallois, that what is called the nervous system, comprehends two dis- tinct systems, the sensorial, and the nervous sys- tem properly so called. Now, it does not appear that galvanism can perform any of the functions of the sensorial system, yet, in the greater number of instances in which it has been used in medi- cine, it has been expected to restore the sensorial poAver. It has been expected to restore hearing, and sight, and voluntary power. It may now and then happen in favourable cases, from the connection which subsists between the sensorial and nervous systems, that by rousing the energy * Many of the following observations on Galvanism are re-published from a paper which the Royal Society did me the honour of publishing in the Philosophical Transactions of this year. x See Chap. 10, and the experiments there referred to. 303 of the latter, we may excite the former. It would be easy to shew, that we have little reason to ex- pect that this Avill often happen; We have also reason to believe from the experiments which have been laid before the reader, that galvanism has no other power over the muscular system, than that of a stimulus ;* we are, therefore to ex- pect little more advantage from it in diseases de- pending wholly on faults of the sanguiferous sys- tem, than from other stimuli. Hence its failure in tumors, &c. But I cannot help regarding it as almost ascertained, that in those diseases in which the derangement is in the nervous, power alone, where the sensorial functions are entire, and the vessels healthy, and merely the power of secre- tion, which seems immediately to depend on the nervous system, is in fault, galvanism will often prove a valuable means of relief. Of Asthma and Dyspepsia. As soon as the foregoing view of the subject presented itself, I was led to inquire, Avhat dis- eases depend on a failure of nervous influence. The effect on the stomach and lungs, of divid- ing the eighth pair of nerves, f auswered the * Compare the experiments related in the first and second Chapters of this part of the Inquiry with Exp. 46,47,48,49, and the observations which follow them. t Exp. 44, 45. 304 question respecting two of the most important diseases of this class. We have seen that with- drawing a considerable part of the nervous in- fluence from the stomach and lungs deranges the digestive powers, and produces great difficulty of breathing. The following observations relate chiefly to affections of the lungs. Of the effects of galvanism in dyspepsia, the principal experi- ence which I have yet had, has been in cases where it was complicated Avith asthmatic breath- ing. When the effect of depriving the lungs of a con- siderable part, of their nervous influence is care- fully attended to, it will be found, I think, in all respects similar to a common disease, which may be called habitual asthma, in which the breath- ing is constantly oppressed, better and worse at different times, but never free, and often continues to get worse, in defiance of every means we can employ, till the patient is permanently unfitted for all the active duties of life. The animal, in the above experiment, is not affected with the croaking noise and violent agitation which gene- rally characterise fits of spasmodic asthma. This state we cannot induce artificially, except by means which lessen the aperture of the glottis. We have seen, from repeated trials, that both the oppressed breathing and the collection of phlegm, caused by the division of the eighth pair of nerves, may be prevented by sending a stream 305 of galvanism through the lungs.* That this may be done with safety in the human body we know from numberless instances, in which galvanism has been applied to it in every possible way. Such are the circumstances Avhich led me to expect relief from galvanism in habitual asthma. It is because that expectation has not been dis- appointed, that I trouble the reader with the fol- lowing account of its effects. Although the effects of galvanism in habitual asthma have been wit- nessed by many other medical men, I have men- tioned nothing in the following pages which did not come under my own observation. I have employed galvanism in many cases of habitual asthma, and almost uniformly with relief. The time, during which the galvanism was ap- plied, before the patient said that his breathing was easy, has varied from five minutes to a quar- ter of an hour. I speak of its application in as great a degree as the patient could bear without complaint. For this effect I generally found from eight to sixteen four-inch plates of zinc and copper, the fluid employed being one part of mu- riatic acid, and twenty of water, sufficient. Some require more than sixteen plates, and a few can- not bear so many as eight; for the sensibility of different individuals to galvanism is very differ- ent It is curious, and not easily accounted for, # Exp. 46, 47, 48, 49. 41 306 that a considerable power, that perhaps of twenty- five or thirty plates is often necessary on first applying the galvanism, in order to excite any sensation; yet after the sensation is once excited, the patient shall not perhaps, particularly at first, be able to bear more than six or eight plates. The stronger the sensation excited, the more speedy in general is the relief. I have known the breathing instantly relieved by a very strong power. I have generally made it a rule to begin with a very weak one, increasing it gradually at the patient's request, by moving one of the wires from one division of the trough to another, and moving it back again when he complained of the sensation being too strong. It is convenient for this purpose to charge with the fluid about thirty plates. The galvanism was applied in the following manner. Two thin plates of metal about two or three inches in diameter, dipped in water, were applied, one to the nape of the neck, the other to the pit of the stomach, or rather lower. The wires from the different ends of the trough* were brought into contact with these plates, and, as observed above, as great a galvanic power main- tained, as the patient could bear without com- plaint. In this Avay the galvanic influence was * I found a trough of the old construction answer better than the improved pile, which is so much superior for most purposes. 307 sent through the lungs, as much as possible, in the direction of their nerves. It is proper, constantly to move the wires upon the metal plates, particu- larly the negative wire, otherwise the cuticle is injured in the places on which they rest. The relief seemed much the same, whether the posi- tive wire Avas applied to the nape of the neck, or the pit of the stomach. The negative Avire gene- rally excites the strongest sensation. Some pa- tients thought, that the relief was most speedy,, Avhen it was applied near the pit of the stomach. The galvanism was discontinued as soon as the patient said that his breathing was easy. In the first cases in which I used it, I sometimes pro- longed its application for a quarter of an hour, or twenty minutes, after the patient said he was perfectly relieved, in the hope of preventing the early recurrence of the dyspncea; but I did not find that it had this effect. It is remarkable, that in several who had laboured under asthmatic breath- ing for from ten to twenty years, it gave relief quite as readily as in more recent cases ; which proves, that the habitual difficulty of breathing, even in the most protracted cases, is not to be ascribed to any permanent change having taken place in the lungs. With regard to that form of asthma which re- turns in violent paroxysms, with intervals of per- fectly free breathing, I should expect little advan- tage from galvanism in it, because, as I have just 308 observed, I found that the peculiar difficulty of breathing, which occurs in this species of asthma, cannot be induced in animals, except by means lessening the aperture of the glottis. It is pro- bable, that in the human subject the cause pro- ducing this effect is spasm, from which indeed the disease takes its name, and we have no rea- son to believe, from what we know of the nature of galvanism, that it will be found the means of relaxing spasm. The spasmodic asthma is, fortunately, a very rare disease, so much so, that but one case of it has occured to me since I have employed galvan- ism in asthma, while I have had an opportunity of employing this remedy in about forty cases of the habitual form of the disease. I cannot, there- fore, from experience, speak with certainty of the effect of galvanism in the former. In the above case it was twice employed in the paroxysm, and I could observe no relief from it. In both in- stances, the patient said that, had it not been used, the symptoms would have been more severe. In this patient, the spasmodic paroxysm was often succeeded by a state of habitual asthma for seve- ral weeks, in Avhich galvanism gave immediate, but temporary relief. Of the above cases of habitual asthma, many occurred in work-people of the town where I re- side, who had been obliged to abandon their em- ployments in consequence of it, and some of them, 309 from its long continuance, without any hope of returning to regular work. Most of them had tried the usual means in vain. By the use of galvanism they were relieved in different degrees, but all sufficiently to be restored to their employ- ments. I have seen several of them lately, who, although they have not used the galvanism for some months, said they had continued to work Avithout any inconvenience. Some, in whom the disease had been wholly removed, remain quite free from it; some have had a return of it, and have derived the same advantage from the gal- vanism as at first. I have confined the application of galvanism to asthmatic dyspncea. I think there is reason to believe, from the experiments which have been laid before the reader, that in inflammatory cases it would be injurious, and, in cases arising from dropsy, or any other mechanical impediment, little or nothing, it is evident, is to be expected from it. Habitual asthma is often attended with a languid state of the biliary system, and some fullness and tenderness on pressure near the pit of the stomach. If the last is considerable, it must be relieved previous to the use of the gal- vanism. In a paper which the Medico-Chirurgi- cal Society did me the honour to publish in the seventh volume of their Transactions, I have en- deavoured to shew that a species of pulmonary consumption arises from a disease of the digestive 310 organs. Many of the observations there made apply to certain cases of asthma ;* I believe to cases of every species of this disease, but parti- cularly of that we are here considering. Many cases of habitual asthma will yield to the means recommended in the above paper, but I have learned, from a pretty extensive experience, that a large majority of such cases will resist them, yet readily admit of relief from galvanism. If there is little tendency to inflammation, galvanism seems also to be a means of relieving the affection of the digestive organs. I have repeatedly seen from it the same effect on the biliary system which arises from calomel; a copious bilious discharge from the bowels coming on within a few hours after its employment. This seldom happens ex- cept where there appears to have been a failure in the secreting power of the liver, or a defective action in the gall tubes. I have not found that the presence even of a se- vere cough, which is common in habitual asthma, in which there is always more or less cough, coun- ter-indicates the use of galvanism. The cough under its use generally becomes less frequent in proportion as the accumulation of phlegm in the lungs is prevented; but it seems to have no direct effect in allaying it. In some cases the cough con- * See the observations on the state of these organs in astl;1 ma, in Dr. Bree's work on this disease. *31i tinued troublesome after the dyspncea had disap- peared. Galvanism never appeared to increase it, except when the inflammatory diathesis was considerable. In some labouring under the most chronic forms of phthisis, in whom the symptoms had lasted several years and habitual asthma had supervened, the relief obtained from galvanism was very great, notwithstanding some admixture of a pus-like substance in what was expectorated. I need hardly add, after what has been said, that in ordinary cases of phthisis nothing could be more improper than the use of galvanism. The dyspnoea arising from phthisis and that from ha- bitual asthma are easily distinguished. The for- mer is less variable. It is generally increased by the exacerbations of the fever, and abvays by ex* ercise. When the patient is still and cool, except in the last stages of phthisis, his breathing is ge- nerally pretty easy. The latter is worst at par- ticular times of the day, and frequently becomes better and worse without any evident cause. At the times when it is better the patient can often use exercise without materially increasing it. Changes of the weather influence it much. It is particularly apt to be increased by close and foggy weather. Phthisical dyspncea is seldom much influenced by changes of the weather, except they increase the inflammatory tendency. When there is a considerable tendency to in- flammation in habitual asthma, the repeated ap- 312 plication of galvanism sometimes increases it so much, that the use of this influence no longer gives relief, till the inflammatory tendency is sub- dued by local blood-letting. It always gave relief most readily, and the relief was generally most permanent, in those cases Avhich were least com- plicated with other diseases, the chief complaint being a sense of tightness across the region of the stomach, impeding the breathing. The pa- tients said, that the sense of tightness gradually abated while they were under the influence of the galvanism, and that as this happened their breath- ing became free. The abatement of the tightness was often attended with a sense of warmth in the stomach, which seemed to come in its place. This sensation was most frequently felt when the nega- tive wire was applied near the pit of the stomach, but the relief did not seem less when it was not felt. With respect to the continuance of the relief obtained by galvanism, it was different in differ- ent cases; in the most severe cases it did not last so long as in those where the symptoms were slighter, though of equal continuance. This observation, however, did not universally apply. When the patient was galvanised in the morning, he generally felt its good effects more or less till next morning. In almost all, the repetition of the galvanism gradually increased the degree of permanent relief. Its increase was much more 313 rapid in some cases than in others. The per- manency of the good effects of galvanism in the disease before us, has appeared very remarkably in several cases where the symptoms, after hav- ing been removed by it, were reneAved after in- tervals of different duration by cold or other Causes. In these cases means which, previous to the use of galvanism, had failed to give relief, Were now successful without its aid; or with few applications of it, compared with those which had been necessary in the first instance. I have not yet seen any case, in which galvanism had been of considerable advantage, Avhere its good effects appeared to have been Avholly lost. It is now about a year and a half since I first employed it in habitual asthma. Taking cold, and the ex- cessive use of fermented liquors have been the principal causes of relapse. The galvanism was seldom used more than once a day. In some of the more severe cases it was used morning and evening. About a sixth part of those who have used it appear, as far as we yet know, to have obtained a radical cure. It in no case failed to give more or less relief, provided there was little inflammatory tendency. It failed to give considerable relief only in about one-tenth; I may add, that were it only the means of present relief, we have reason to believe that, as being more innocent, it would be found pre- ferable to the heating, spirituous, and soporific- 42 314 medicines, which are so constantly employed in this disease. As it often happened that a very small gal- vanic power, that of not more than from four to six four-inch double plates, relieved the dyspncea, may we not hope, that a galvanic apparatus may be constructed, which can be worn by the patient, of sufficient power to prevent its recurrence in some of the cases in which the occasional use of the remedy does not produce a radical cure ? I wished to try, if the impression on the mind, in the employment of galvanism, has any share in the relief obtained from it. I had not at this time seen its effects in apoplexy. I found that by scratching the skin with the sharp end of a Avire I could produce a sensation so similar to that excited by galvanism, that those who had most frequently been subjected to this influence were deceived by it. By this method, and arranging the trough, pieces of metal, &c. as usual, I de- ceived several who had formerly received relief from galvanism, and also several who had not yet used it. All of them said that they experienced no relief from what I did. Without allowing them to rise, I substituted for this process the real application of galvanism, merely by immersing in the trough one end of the wire with Avhich I had scratched the nape of the neck, the wire at the pit of the stomach having been all the time applied as usual by the patients themselves. Before the 315 application of the galvanism had been continued as long as the previous process, they all said they were relieved. I relate the particulars of the two following experiments, because independently of the principal object in view in making them, they point out two circumstances of importance in judg- ing of the modus operandi of galvanism in asth- matic cases. The first Avas made on an unusually intelligent lady, of about thirty-five years of age, who had for many years laboured under habjtual asthma, than whom I have known none more capable of giving a distinct account of their feelings. Her breathing was very much oppressed at the time that she first used galvanism. The immediate effect was, that she breathed with ease. She said she had not breathed so well for many years. Part of the relief she obtained proved permanent, and, when she Avas galvanised once a day for about ten minutes, she suffered little dyspncea at any time. After she had been galvanised for eight or ten days, I deceived her in the manner just mentioned. The deception Avas complete. She told me to increase or lessen the force of the gal- vanism, as she Avas accustomed to do, according to the sensation it produced. I obeyed her di- rections by increasing or lessening the force with which I scratched the neck with the wire. After I had done this for five minutes, she said the gal- vanism did not relieve her as usual, and that she 316 felt the state of her breathing the same as Avhen the operation was begun. I then allowed the gal- vanism to pass through the chest, but only through the upper part of it, the wire in front being ap- plied about the middle of the sternum. She soon said that she felt a little relief; but although it was continued in this way for ten minutes, the re- lief was imperfect. I then directed her to apply the wire in front to the pit of the stomach, so that the galvanism passed through the whole extent of the chest, and, in a minute and a half, she said her breathing was easy, and that she now experi- enced the whole of the effect of the former appli- cations of the remedy. To try how far the effect of galvanism in asth- ma arises merely from its stimulating the spinal marrow, in a young woman who had been seve- ral times galvanised in the usual way, the wires were applied to the nape of the neck and small of the back, and thus the galvanic influence was sent along the spine for nearly a quarter of an hour. She said her breathing was easier, but not so much so as on the former applications of the galvanism ; and on attempting to walk up stairs she began to pant, and found her breathing, when she had gone about half way, as difficult as before the gal- vanism was applied. She was then galvanised in the usual way for five minutes : she now said her breathing was quite easy, and she walked up the whole of the stairs without bringing on any 317 degree of panting, or feeling any dyspnoea. The above experiment was made in the presence of four medical gentlemen. This patient, after re- maining free from her disease about half a year, returned to the Infirmary, labouring under a slighter degree of it, and experienced immediate relief from galvanism. The disease seemed to have been renewed by cold, Avhich had at the same time produced other complaints. This is one of the cases above alluded to in speaking Of the permanency of the good effects of galvanism. On the return of this patient to the Infirmary, two or three applications of galvanism, combined with means which had given no permanent relief to the dyspncea previous to her first using galvan- ism, now soon removed it. When she first used galvanism, it required its constant employment once or twice a-day for several Aveeks to produce the same effect. There is reason to believe she Avill remain well if she can avoid taking severe colds. Many medical gentlemen have frequently wit- nessed the relief afforded by galvanism in habitual asthma, and Mr. Cole, the house surgeon of the Worcester Infirmary, authorises me to say, that no other means there employed have been equally efficacious in relieving this disease. Observations similar to the foregoing, there is reason to believe, will be found to apply to 318 dyspepsia, but as I have made but few trials of galvanism in this disease, except where it was complicated with asthma, the removal of which no doubt contributed to a more healthy action of the digestive organs, I cannot yet speak with certainty of its effects in this disease. In some, galvanism, at the time of its application, occasions a tendency to sighing; and in some, in whom it removed the dyspncea, it seemed to occasion a sense of sinking referred to the pit of the sto- mach. This occurred in several instances, and Avas relieved by small doses of carbonate of iron and bitters. That I may convey to the reader as correct an idea as I can of the effects of galvanism in habitual asthma, I shall concisely relate the par- ticulars of a few of the most, and of the least, successful cases, in which it was employed. Richard Morgan, a blacksmith, set. 50, had laboured under severe habitual asthma for seven months, during which he had been better and worse for a few weeks, but never free from dysp- ncea. He was much troubled with a cough, the expectorated matter being thick, and of a yellow- ish colour. The dyspnoea was particularly severe at the time he was galvanised, and had been so for about a fortnight. The first application of the galvanism relieved him. He was galvanised only for three days, about ten minutes each day, before 319 he declared himself to be perfectly well. He re- turned to his work, which he had been obliged to abandon, after the second application of the gal- vanism. After its third application he performed as hard work, and with as much ease, as he had ever done. He remained free from dyspncea till it was re- newed, several weeks afterwards, by his getting drunk. Galvanism relieved him as readily and effectually as at first. It is now ten months since he first used this remedy, during which he has had several returns of dyspncea, but it has never been so severe as before he was galvanised; and when it has been such as to induce him to have recourse to galvanism, he has always experienced from it immediate relief. He ascribes the returns of his disease to his being exposed to severe and sudden heats and chills. Mary M'Konchy, set. 28, a gloveress, had been afflicted with habitual asthma for four years, and under my care about one year, during Avhich she had tried all the usual means with very imper- fect relief; she had some languor in the biliary system, but little inflammatory tendency. The breathing was, in a few minutes, rendered easy by galvanism, and after the second application of it, it remained so. She noAV experienced no in- convenience from exercise, which had not at any time been the case for four years. 320 In about three weeks after she had been gal- vanised she experienced some return of the dyspnoea. It was wholly removed by a blister, which had often been tried, previous to her being galvanised, with "but little and very temporary relief. She complained of a sense of sinking at the stomach for some time after the use of the gal- vanism, which was removed by carbonate of iron and bitters. This effect of galvanism seemed often to be most felt when it gave most relief to the dyspnoea, seeming to come in place of the latter. I have hitherto found it easily removed by the above means. It is now many months since this patient was galvanised, and she re- mains well. Hannah Cooke, »t. 20, a servant, had labour- ed under habitual asthma for tAvo months, and tried various medicines without relief. She was in a few minutes relieved by galvanism, and after three applications of it, remained quite Avell. It is now five or six weeks since she was galvanised. I could mention several other cases, in which I witnessed the same sudden and permanent re- lief from galvanism, as in those here related. Isaac Radley, set. 68, a labourer, formerly a soldier, had been ill 14 years. His asthma was caused by sleeping in camp in Holland. He had never been able, during the above time, to walk 321 at the usual pace Avithout bringing on the dysp- noea, although he had sometimes been pretty free from it Avhen he Avas still; at other times he had been constantly oppressed with it, and obliged wholly to abandon his work. At the time he used the galvanism, he was affected with the most se- vere dyspncea, which only allowed him to move, and that with difficulty, at the slowest pace; he had been in this state for half a year. This was the longest and most severe fit he had ever had. He Avas relieved in a few minutes by the applica- tion of galvanism. He could perceive its bene- ficial effects for twenty-four hours after its appli- cation. It was used daily with the same imme- diate relief. Its permanent good effects gradually encreased, and after he had been galvanised for about ten minutes each day, for between two and three weeks, his breathing remained quite easy. He could now not only walk, but, as I several times Avitnessed, run without any dyspnoea. He complained of the sense of sinking at the pit of the stomach after the dyspnoea had left him, which, as in the case just mentioned, was readily removed by the carbonate of iron and bitters. He now said his digestion was much better than it had been previously to the use of the galvanism. Those wljose breathing had been much relieved by galvanism, often made this observation, al- though they had not experienced the sense of sink - 43 322 ing, and consequently had used no stomachic me- dicines. I saw this man, several months after he had ceased to use galvanism, working as a bricklayer's labourer. He said he had no feeling of dyspnoea, and had been quite free from it since he had used the galvanism. In general, where galvanism gave such com- plete and permanent relief, as in Badley's case, its effects were more speedy, some degree of dysp- ncea for the most part remaining in protracted cases. The folloAving are the most unsuccessful cases, which either Mr. Cole or I could recollect. Martha Davies, a servant, set. 40, had laboured under habitual asthma for five years. She was relieved on the first application of galvanism, and said her breathing was quite easy; but she was not always equally relieved by it, sometimes it gave comparatively little relief. The more per- manent relief afforded, was also different at dif- ferent times, never complete. She was galvan- ised for about three weeks, but not daily, her business preventing her regular attendance ; she used the remedy in all about thirteen or fourteen times. It was impossible to prevent her drink- ing a great deal too much malt liquor. It is now about half a year since she was gal- 323 vanised, during which she says both her breath- ing and digestion have been better than for the preceding five years. She thinks the digestion as much improved as the breathing. She has had no very bad attacks of dyspnoea, and has been much less subject to bilious attacks. She is now occasionally so well that she can run without in- convenience, which she could never do during the above time, but, in general, her breathing, though in a less degree than formerly, is still op- pressed. Mary Clark, a servant, set. 24, had laboured under habitual asthma for about a year. The dyspncea was always quickly relieved by the galvanism, although she seemed to experience lit- tle, if any, permanent relief from it. She had more pain in the stomach than is usual in such cases, and the galvanism seemed to increase it. She wras cured by an alternative course of medi- cines and evacuations from the region of the sto- mach, and did not use galvanism for the last fort- night. She had used it at first daily for a fort- night, and twice afterwards for a Aveek each time. As far as I can judge from having observed the course of many cases of this kind, her recovery would neither have been so speedy nor complete if she had not used galvanism. Rachel Hooper, set. 29, a servant, had laboured 324 under severe habitual asthma for about a year, with considerable inflammatory tendency. Her breathing was relieved in a few minutes by gal- vanism, but not completely. For about eight or ten days, during which she Avas galvanised daily for about ten minutes, she derived from it con- siderable relief, both immediate and permanent. It then began to fail to give relief, and in a few days gave none. The epigastric region was now very tender on pressure. This symptom was relieved in the space of a few days by local blood- letting, blistering and small doses of calomel. The relief afforded by the galvanism was now greater than at first, which seemed to arise from the disease not being so severe as on the first use of the remedy, for some part of the good effects of the galvanism had remained. After this she was always relieved by it as long as she conti- nued to use it, which was for several weeks. The permanent relief she experienced from it was also great, although she still at times laboured under a considerable degree of dyspncea. About half a year ago, she left Worcester with a pro- mise to return, if she should get Avorse. I have heard nothing of her since. She said nothing else had given her so much, either immediate or permanent relief, as the gal- vanism had done. She had been for several months in the Infirmary under other plans of treatment before she used the galvanism. All 325 the patients whose cases I have mentioned were galvanised at the Infirmary. The following is a remarkable instance of per- manent, though imperfect relief, from galvanism, in the disease before us. A woman, who had for many years laboured under severe habitual asth- ma, was incautiously galvanised with such a power as occasioned severe pain. No entreaty could induce her to submit to a repetition of the galvanism, although it had immediately relieved her breathing. The dyspnoea soon recurred, but she told me many months afterwards that it had never been so severe since she was galvanised, and that she had ever since been able to carry water in buckets from the river, which the state of her breathing had not for a long time pre- viously allowed her to do. If the reader will compare these cases with the general observations which I have had occasion to make on the effects of galvanism in habitual asthma, he will be enabled to form a pretty cor- rect estimate of what he may expect from its em- ployment in this disease. When we compare them with the experiments laid before the reader in the preceding Inquiry, the question naturally arises, whence proceeds the permanent relief obtained in them ? The galvanic experiments lead us to expect relief to the dysp- 326 noea while the stream of galvanism passes through the lungs ; but on what principle shall we explain the permanency of the relief afforded ? The fol- loAving observations appear to throw some light on this subject. There are two ways in which an organ may be deprived of its nervous influence, either by a failure of due action in the brain and spinal marrow, the sources of nervous influence, or a failure of due action in the nerves of the or- gan affected, by which this influence is conveyed. It is no longer conveyed by a nerve which has been divided, or around which a ligature has been thrown. Now we have reason to believe that ha- bitual asthma arises not so much from a fault in the brain and spinal marrow, as in the nerves of the lungs; because, did the degree of dyspnoea, Avhich we often witness in this disease, arise from failure in the general source of nervous influence, this failure must be sufficient to appear in the de- rangement of all the nervous functions; whereas in habitual asthma, Ave often find the function of the lungs alone affected; and when general fail- ure of nervous influence is observed, it is evidently the effect of impeded respiration, appearing only after the latter has continued for some time, and varying as it varies. The effect produced by gal- vanism, when it performs a cure in habitual asth- ma, therefore, does not appear to be its having occasioned a permanent supply of nervous in- fluence, but its having cleared, if I may use the 327 expression, the passage of this influence to the lungs. It is not difficult to conceive that such an obstruction may exist in the nerves as cannot be overcome by the usual supply of nervous influence, though it may yield to a greatly increased supply of it; and that it may in some cases continually recur in an equal or diminished degree, while in others, being once removed, the tendency to it may cease.* The foregoing observations seem to explain why other means, which give a temporary vi- gour to the nervous system, often, for the time, relieve habitual asthma ; and sometimes, though rarely, cure this disease. The relief obtained from such means being in general so much less than that obtained from galvanism, I Avould as- cribe to the former occasioning but little addition- al supply of nervous influence, while by the latter we can make the additional supply as great as we please. * What is here said is well illustrated by the effects of gal- vanism in apoplexy. We know that in this disease the dysp: ncea arises from a failure in the source of nervous influence, and the relief obtained from galvanism corresponds with the views afforded by the experiments which have been laid be- fore the reader. While the galvanism passed through the lungs the dyspncea was as much relieved as in habitual asth- ma, but when it ceased to pass through them, the relief lasted no longer than was necessary for the re-accumulation of the phlegm. 328 Of Suspended Animation. The last disease which I shall mention is sus- pended animation from drowning, or other causes obstructing the breathing. Inflating the lungs seems here to act in two ways. It gives to the blood of the smaller vessels of the lungs the arte- rial properties by which they are excited to ac- tion ; and acting through the blood of these ves- sels, it communicates to that of the larger vessels, and of the heart itself, more or less of the same properties, independently of the blood already changed being moved on towards this organ; for M. le Gallois has shewn, that after the circula- tion has permanently ceased, the blood may be changed, by inflating the lungs, not only in the heart itself, but also in some part of the larger arteries. By these means the circulation in the lungs is restored, but it is evident from the expe- riments which have been laid before the reader, that their due action cannot be restored till they receive their usual supply of nervous influence. Now this cannot happen till the re-established circulation has renewed the vigour of the brain and spinal marrow. We have reason to believe, that could the due degree of this influence be re- stored to the lungs as soon as the circulation is renewed in them by the access of the air, they 329 would be excited to a more perfect performance of their functions ; and that recovery might thus be effected in some cases, where inflation of the lungs alone would fail. We have seen, from direct experiment, that galvanism can supply the place of nervous influ- ence in the lungs, enabling them to perform their functions after the latter is withdrawn. I would therefore propose, that, to the means employed for the recovery of suffocated persons, an appara- tus, properly adapted for sending a stream of gal- vanism through the lungs in the direction of their nerves, as above pointed out, should be added. It would be improper here to employ, for any con- siderable length of time, a stronger power than experience has taught us can be used without bad effects in health. The power should not exceed that of fifteen, or at most, twenty-four inch double plates of zinc and copper, the fluid being one part of muriatic acid and twenty of water. I should expect little advantage from galvan- ism applied to any other secreting organ, because the revival of the patient depends little, if at all, on the action of any other. Employed as a ge- neral stimulus to the brain and spinal marrow, it may be of use by rousing the dormant powers of the system. They are all, we have seen, capa- ble of being excited through these organs. In this way it can only indirectly assist the lungs, 44 330 and that chiefly in proportion to the degree in which general circulation is restored. It is pro- bable, that, as a general stimulus, a greater power of galvanism may be used without injury, than it would be proper to send through any vital organ for a considerable length of time, because, em- ployed with this view, it may be applied inter- ruptedly. Of Sympathy. Do not the experiments which have been laid before the reader tend to throw some light on the nature of the sympathy which exists between different parts of the body, and so extensively influences the symptoms and treatment of dis- eases?* If it appears that the nervous influence is not only capable of exciting, and acting as a sedative to, the moving fibre wherever it exists, and whether subject to the will or not,f and of influencing in every possible way the secreting process,f but is itself of such a nature, that it is capable of pervading equally the solids and fluids * I have, in a paper above referred to, published in the seventh volume of the Medico-Chirurgical Transactions, enumerated some of the more striking instances in which the sympathy of parts influences the symptoms and treat- ment of diseases. t Part II. Chap. 2. \ Chap. 5, Sec. 1 and 3. 331 of the body, and of being instantly moved from place to place independently of any immediate connection of vessels or nerves,* it will not be difficult to explain the various phenomena of sympathy, many of which, at first view, appear so unaccountable. * Chap. 5, Sec. 2. The phenomena of sympathy seem always to take place through the intervention of the brain or spinal marrow. APPENDIX. The following account of an experiment which, I am informed, is supposed by many to contra- dict the result of the galvanic experiments which have been laid before the reader,* was sent to me. " Two rabbits, which had had no food for se- venteen hours, were allowed to eat parsley. The nerves of the were then divided in the neck of each. One of them was allowed to re- main quiet. A slip of tin foil was connected to the lower divided ends of the nerves of the other rabbit, and another piece of tin foil, an inch square, was applied to the abdominal muscles over the stomach, and under the integuments, by means of a wound in the latter. The tin foil over the stomach was connected with a wire communi- cating with one end of a voltaic battery of twenty plates, and occasional contacts were made, (about three or four times a minute,) between a wire con- nected with the other end of the battery and the tin foil in the neck. The influence of the battery was sufficiently strong to excite slight contrac- tions of the muscles of the fore-legs. This pro- * Exp. 46, 47, 48, 49. 334 cess was continued during five hours, at the end of which period both rabbits were killed. "On examining the stomach of the animal, which had been subjected to the influence of the battery, it was found much distended with food; the parsley was principally in the cardiac portion, and near the oesophagus it appeared to have un- dergone no alteration; and below this it was mixed with the other food in the stomach, so that no accurate observation could be made on it. " The stomach of the other rabbit was exa- mined by the side of the first, so that they might be compared together, and the appearances were precisely the same with those which have been just described. The contraction in the centre of the stomach was somewhat greater in the galvan- ised stomach than in the other." It is perhaps unnecessary to observe that this experiment, except in the most unimportant cir- cumstances, bears no resemblance to any of the galvanic experiments related in the preceding In- quiry. In the above account of it, which is printed in the way it was sent to me, it is not stated what nerves were divided, and no symp- tom is mentioned which can lead us to suppose that they were the nerves of the eighth pair; while the appearances after death demonstrate that these nerves had not been divided, the state of the contents of the stomachs of both rabbits be- ing such as it is never found to be, when they 335 have been divided some hours previous to death.* Had the proper nerves been divided, the experi- ment would still have been inconclusive, as far as relates to my experiments, because no con- tinued stream of galvanism was sent through the stomach, but only "occasional contacts" of the metals were made. It is unnecessary to point out some minor circumstances, in which the above experiment differs from the galvanic experiments in question. In repeating such experiments, it is evident, every circumstance should be carefully considered. Even trivial differences in the mode of making them often occasion essential differences in the result. * Page 161 et. seq. THE END.