^ /^' /i^t ' I' ';£Si,i i/T^^jJ/j^ *«'fesy; l^^l y>£S /^::^[' ■'^ .^^ Boston Medical Library in the Francis A.Countwdy Libraryof Medicine -Boston Digitized by the Internet Archive in 2011 with funding from Open Knowledge Commons and Harvard Medical School http://www.archive.org/details/experimentsonnerOOmonr k c^^- EXPERIMENTS "" ON THE NERVOUS STSTEM, WITH OPIUM AND METALLINE SUBSTANCES ; MADE CHIEFLY WITH THE VIEW OF DETERMINING THE NATURE AND EFFECTS OF ANIMAL ELECTRICITY. BY ALEXANDER MONRO, M. D. PROFESSOR OF MEDICINE, ANATOMY ANB SURGERY IN THE UNIVERSITY OF EDINBURGH; FELLOW OF THE ROYAL COLLEGE OF PHYSICIANS, AND OF THE ROYAL SOCIETY OF EDINBURGH, AND OF THE ROYAL ACADEMY OF SURGERY IN PARIS* EDINBURGH: PRINTED BY ADAM NEILL A N t) COMPANYji FOR BELL & BRADFUTE^ AND T. DUNCAN} AND J. JOHNSON, LONDON. M.DCCXClIIa // 9 3£ fel CONTENTS. Tage INTRODUCTION, - ^ . . _ i Obfervations on the Circulating and Nervous Syflems of Frogs, ^ - - „ _ 5 Experiments with Opium, - « ., ^ p Corollaries from the above Fads and Experiments, - 12 Summary of Experiments made on Animals with Me- talline Subflances, - - - _ i^ Summary of Fadls proved by the foregoing Experi- ments, - - - - - - 35 kefemblance of the Fluid put in Motion by the fore- going Experiments to the Eledlrical Fluid, - 38 The Nervous Fluid or Energy not the fame with the ' Eleftrical, nor with the Fluid put in Motion by the foregoing Experiments, - - - 40 General Conclufions, - - - - 42 INTRODUCTION. l^XTHEN, in November laft, I began to make Experi- ments on Animal Eledricity, of which I read fome account to the Royal Society on the 3d of December ; I was not only much hurried with bufinefs, but could not procure a fufEcient number of Frogs for the purpofe. Du- ring the laft winter and fpring, I profecuted the fubjed: more fully and with greater attention ^ and, on the third day of June, I read a fecond paper to the Royal Society, to which I have, fince that time, made additions. I ihall now Hate a fummary of the chief circumflances I have obferved, with a few Remarks. A O B S E R- OBSERFJflO NS on the OBSERVATIONS on the CIRCULATING and NER= VOUS SYSTEMS of FROGS, As my Experiments with Opium, as well as thofe on Animal Eledlricity, have been performed on Frogs chiefly j I fhall premife fome obfervations on their Circulating and JNervous Syfl;ems. Their Heart confifls of one Auricle and one Ventricle only, their Aorta fupplying their Air Velicles or Lungs, as well as all their other Organs 5 and, of courfe, their Venae Cavse return the Blood from all parts to the Heart. The Ventricle of their Heart contrails about lixty times in a minute ; and the purple colour of the Blood which is feen within it, difappears after each contraction, or the Blood is entirely expelled by its contradion. For upwards of an hour after cutting out its Heart, a Frog can crawl or jump ; and, for upwards of half an hour longer, it contradls its Legs NERVOUS SrsTEM. 7 Legs when the Toes are hurt, though not with fufficlent force to more its Body from the place where it is laid. Their Encephalon confifts of Brain and Cerebellum, each of which, on its upper part, is divided into two He- mifpheres ; and, below, they are conjoined by thick Crura, which form the Medulla Oblongata and Spinal Marrow, both of which are proportionally larger than in Man, and more evidently confift of two Cords. There are nine true Vertebrae j and at the fixth of thefe, the Spinal Marrow terminates in the Cauda Equina. The Sciatic Nerves are formed by three pairs of Nerves, fent out below the feventh, eighth and ninth Vertebrae, and by one pair from the Os Sacrum. A Nerve, refembling our great Sympathetic Nerve, paffes downwards from the Abdomen into the Pel- vis. Two days after cutting off the Head of a Frog at its joining with the firft Vertebra, I found it fitting with its Legs drawn up, in their ufual poflure j and when its Toes w^ere hurt, it jumped with very confiderable force. Its Heart likewife continued to beat about forty times in a mi- nute, and fo llrongly as to empty itfelf and circulate the Blood. A 2 In 8 OBSERVATIO NS on the In feveral Frogs, after cutting off the back part of the fix undermofl true Vertebrae, I took out all that part of the Spmal Marrow with the Cauda Equina which they cover. The lower Extremities were rendered infenfible to common injuries, and lay motionlefs 5 yet the Frogs lived feveral months thereafter, and the wounded parts of their Backs cicatrifed ; and the Bones of their Legs, which I fradured, were re-united, the Blood circulating freely in their Veflels. It is univerfally known, that if, after amputating the Limb of a warm blooded Animal, we repeatedly irritate the Nerves which terminate in Mufcles, repeated Convul- fions of the Mufcles are for fome time produced 3 and that in Frogs, and other cold blooded Animals, the Nerves retain this power Hill longer. But it has been commonly fuppofed, that, after irri- tating the Nerve a given number of times, the efFed: ceafes, Authors conceiving that there is lodged in the Nerve fome fluid, or other energy which is exhaufted by repeated ex- plofions. Inftead of this, L have found that the time the Nerves preferve their power is the fame, whether we irritate them or not ; or that their energy is not ex- haufted NERVOUS SrSTEM. 9 haufled by Irritation, unlefs the irritation be fuch as fen- libly alters their texture. EXPERIMENTS with OPIUM. I CUT one hole in the fore and upper part of the Cra- nium and Dura Mater of a Frog, and another in the back part of the lowermofl Vertebrae, and then injeded, from the one hole to the other, a fmall fyringe full of water, in five ounces of which one ounce of Opium had been infufed for three days. The infulion, by this means brought into conta6l with the whole furface of the Encephalon and Spi- nal Marrow, produced almoil inflantly univerfal convul- fions ; and, in lefs than two minutes thereafter, the Ani- mal was incapable of moving its body from the place where it was laid. A quarter of an hour thereafter, I found the Heart beating twenty-five times only in the minute 3 and fo feebly, that it could not entirely expel the Blood. When, half IQ 0 BS ERF at: IONS on the half an hour thereafter, the Sciatic Nerves were pinched, a flight tremor only was excited in the Mufcles of the Leg; and Animal Eledlricity produced but feeble twitchings of the Mufcles. The infufion of Opium, injedled in the fame manner In Rabbits and In a Pig, produced fimllar effedts. I HAD long ago * obferved, that an infufion of Opium, poured into the Cavity of the Abdomen of a Frog, after cutting out Its Heart, occafioned. In a few minutes, con- vulfions of Its hind Legs. I have fince found, that, after cutting off the Head, and cutting out the Heart of a Frog, its hind Legs are confiderably weakened by pouring an in- fufion of Opium Into the Cavity of its Abdomen. Although an infufion of Opium poured into the Auricle and Ventricle of the Heart of a Frog, inftantly renders that Organ incapable of contradllon, and, even after the Aorta has been previoufly cut, occafions convulfions of the Legs, yet I have not found that by Opium applied to the Brain, the Spinal Marrow, the Heart, or Abdominal Vlfcera, the Mufcles of the Legs were fo entirely killed as not to per- form » See Edin. Phjf. Eff. Vol. III. 2 NERVOUS ST ST EM. ii form Tome motion when their Nerves were pinched, or when they were aded on by Animal Eledricity. After taking out the lower half of the Spinal Marrow, and likewife cutting tranfverfely all the parts at the Pelvis, except the Crural Arteries and Veins and Lymphatics, which probably accompany them, I found that an infufion of Opium, applied to the Skin and Mufcles of the Legs, affeded the fuperior parts of the Body * : more probably, in my opinion, by abforption, than through any minute remanent branches of the Nerves, efpecially as I do not find, on laying the Veflels fo prepared over a gold probe, and touching with it Zinc laid under the Spine, that con- vulfions of the Legs can be excited. At the fame time, the quantity of Opium abforbed is fo fmall, that I could not diftinguilh its fmell or tafte in the Bloody nor did I find thefe diilinguilhable, in other Experiments, in which the Frogs were violently convulfed after applying the infufion. to the furface of their Skin. Animal Eledricity or different metals applied to the: Head of a Frog, or to any part of its Spine above its fixth Vertebra, do not occafion convulfions of its hind Lees.. COROL- * See Edin. Phyf. EIT. Vol. IIL 12 0 B SERFATIONS on the COROLLARIES from the above FACTS and EX- PERIMENTS. From the above Fads and Experiments, it appears, 1. That the Frog, after its Head Is cut off, feels pain, and, In confequence of feeling, moves its Body and Limbs. 2. As the Nerves of the hind Legs are not affeded by Animal Eledlrlclty, unlefs it be applied lower than the fifth Vertebra, thefe Nerves do not feem to be derived folely or chiefly from the Brain or Cerebellum. 3. As Opium, after the Circulation ceafes, affeds Organs diflant from thofe to which it is applied, it is beyond doubt, that the latter fuffer in confequence of Sympathy of Nerves. 4. It appears that, in this Animal, there is Sympathy of Nerves after the Head is cut off^ or that Sympathy of Nerves NERVOUS SrSTEM. 13 Nerves does not, in this Animal, depend entirely on the connexion of Nerves within the Head. 5. As, after cutting off the Head, this Animal is fufcep- tible of pain, and, in confequence of that, performs volun- tary motion, it appears that, in it, the Brain is not the fole feat of the Senfor'mm Commune. 6. Several weeks after I had taken out the lowermofl: half of the Spinal Marrow, and with it the Cauda Equina, I daily applied, for four days running. Animal Eledricity to the Sciatic Nerves, by pafling a gold Probe between them and the Os Sacrum, and excited feveral hundreds of convuHions of the Thighs and Legs, and yet found that, on laying bare the Femoral Nerves, and pinching them, the Mufcles were flightly convulfed. Hence, I apprehend, additional force is given to an opinion I ventured many years ago to propofe *, that the Nerves do not receive their energy wholly from the Head and Spinal Marrow, but that the texture of every branch of a Nerve is fuch as to furnifh it, or that the ftrudlure of each Nerve is fimilar to that of the Brain. B 7. From * See Obfervations on the Nervous Syftem, 1783, Chap. x. and xi. 14 OB SERF JT 10 NS on the 7. From the above Experiments, it appears probable, in the higheft degree, that Opium may be abforbed in fuch quantity as to produce fatal fymptoms. 8. The following circumflances concur in rendering in- admiflible an opinion lately propofed by M. Font an a, that Poifons operate by changes they produce on the mafs of Blood, or on fome unknown principle connedled with the Blood. a. If his opinion was juil, Poifon introduced into a Vein of the extremities, fo as to be in contadt with this unknown principle, fliould operate as quickly, and in the fame man- ner as when the Poifon is mixed with the Blood near the Heart, which he admits is not the cafe *. b. Cutting the Spinal Marrow in Frogs, before apply- ing the Poifon of the Viper to their Legs, prevents it from killing them f j which fliould not happen, if the Poifon ad- ed on the Blood alone. c. He * See FoNTA na fur les Poifons, 1781, p. 267. ■\ See F IONIAN A, p. 293. NERF-OUS SrsTEM. i^ c. He acknowledges that an Animal bit in its Leg by a Viper, inflantaneoufly feels acute pain *^ and it, in like manner, feels inftantly great uneafmefs when the Poifon is mixed with its Blood f . We know for certain, that, through the medium of the Nerves, we are Inftantly ren- dered fenfible of injury done to the moft diftant parts of our Bodies. Are we not, therefore, in the laft mentioned Experi- ment, to conclude, that the uneafinefs was produced be- caufe the Poifon aded upon the Nerves of the Veflels ? d. In like manner. Animals were convulfed as foon as they were wounded, or received the Poifon into a Blood- veflelj and long before the Blood could have reached the Mufcles in adtion |. e. As foon as the diftilled Water of Lauro-cerafus was poured into the Stomach of a Pigeon, it was convulfed, B 2 and * FONTANA, p. 244. f FoNTANA, p. 359. t FoNTANA, p, 112. p. 259. i6 OB SZRVJT:I0NS^ on the died inftantly *, that is, before the Poifon could have entered theMafs of Blood. f. Many years ago, I found, after cutting the Venae Cayae and Aorta of a Frog, that a watery folution of Opium poured into the Heart, occafioned, in a few minutes, con- vulfions in its Legs ; and, after cutting out the Heart, that the Opium poured into the Cavity of the Abdomen affed- ed the Legs in like manner ^ although, in thefe Experi- ments, the Circulation was not only interrupted, but the greater part of the Blood evacuated. I THEREFORE then concludcd f , and now conclude, that Opium and other Poifons, even after they are mixed with the Mafs of Blood, produce their fatal effedls, chiefly and almoft folely, by ading on the Nerves of the Heart and Vafcular Syftem, and, through thefe, affeding the whole of the Nervous Syftem. SUMMARY * FoNTANA, p. 142. t Edin. Phyf. Eff. publiflied in 1771, ?• 363* NERFOUS SrSTEM, 17 SUMMARY OF EXPERIMENTS made on ANIMALS WITH METALLINE SUBSTANCES. I SHALL now proceed to ftate the feveral clreumftan- Ges I have obferved, in my Experiments, which more diredly lead us to judge of the Nature and Caufe of Animal Eledricity. I. When two Plates of different Metalline Subftances, particularly of Zinc and Gold, between which a living Frog is placed, are brought into contact with each other, thofe Mufcles, which are farther from the Brain and Spinal Mar- row than the Metals, are eonvulfed : and this effed: follows^ although the Animal and Metals are placed on an inverted glafs jar, and that a flick of fealing wax is interpofed be- tween the hand of the Operator and the Metals j that is, although the Animal, with the Metals, be infulated. i8 OBSERVATIONS on the I HAVE further obferved, that the Metals, difpofed as above defcribed, excite convulfions in the Legs, after all the parts of the Frog have been divided tranfverfely at the Pelvis, providing only that they are, thereafter, laid in contad: with each other. 2. When all the parts of a living Frog, except the large Nerves called Sciatic, are cut tranfverfely at the Pelvis, and the fore part of the Animal is laid on a plate of Zinc, fupported by glafs, and the hind Legs on glafs 3 if a gold Probe be applied fo as to touch the Zinc and one of the Legs J or a piece of Metal put under one of the Legs ; the Mufcles of both Legs will be convulfed. The event is the fame, after the Body of the Frog has been cut tranfverfely about the middle of the Spine : or when the Legs are laid on the Zinc and the Spine on Glafs. Ira piece of perforated dry Paper is placed between the gold Probe and the Mufcles, there will be no convulfions ; but wet Paper interpofed does not prevent the convulfions. On feparating the gold Probe from the Mufcles there are no convulfions. 3 3- If» NERFOUS SrsTEM. 19 3. If, after the Animal and Metals are placed as above defcribed, the joining of the two Legs at the Ofla Pubis is cut, that Leg only will be convulfed with which the gold is in contad. 4. The Spine of the Frog with the Zinc being placed on one glafs, and the Legs on another glafs, if the gold, fup- ported by one hand, which we fhall call the Right Hand, be applied to the Zinc alone, and not to the Legs, thefe are not convulfed. But if the Operator applies his left hand to the Legs, or if a byftander, communicating with the Operator by the medium of the floor only, touches them, they are convulfed. If a flick of fealing-wax be interpofed between his right hand and the gold, or between his left hand and the Legs ; or, if the byflander, touching the Legs, is infulated, by ftanding on a flool fupported by glafs feet, the Legs will not be convulfed. If the infli- lated byftander touches the Legs with one hand, and the Operator with his other hand, the Legs are immediately convulfed. 5. After cutting the Spine tranfverfely under the fifth Vertebra, and all the parts of the Pelvis, except the Sciatic Nerves, and laying the Spine on Zinc fupported by glafs, and 20 0 BSERFJTIO NS on the and the Legs on glafs ; if gold be applied to the Zinc, and then to one of the Sciatic Nerves, both Legs, if they have not been feparated from each other at the Olla Pubis, will be convulfed *. And this happens although a ftick of feal- ing-wax be interpofed between the hand of the Operator and the gold Probe, and although no Metalline Subftance touches the Legs. This Experiment fucceeds after denuding the Sciatic Nerves for the length of an Inch, and wiping them dry ; and it continues to fucceed for an hour or more, and till the Nerves are evidently difcoloured and fhrunk In their fize. And, after that, although we wet the Nerves, their powers are not reftoredj fhewing that the Influence had been conveyed not by wetnefs on the furface of the Nerves, but * Very fmall portions of difFerent metals, applied as above defcribed, have aftonifliing efFefts ; and although I have found tliat large portions of the metals produced convulfions, when fmaller had failed, or that they produced flxonger convulfions -, yet the effe£b are by no means proportioned to the weight of the metals employed, nor to the extent of their fiurfaces which are fuddenly brought into contaiSl. In moft of my Experiments, I employed a plate of Zinc, about five inches long, three inches broad, and about one-third of an inch thick ; and a gold Probe, fomewhat thicker and longer than the Probes Surgeons commonly ufe. NERVOUS SrS'tEM. 21 but by the particular matter of which Nerves are com- pofed. The event is the fame, when the upper ends of the Scia- tic Nerves are cut away from the Spine, and laid on the Zinc. 6. After preparing the Frog and placing the Metals as in laft Experiment, if a piece of thin dry Paper, pierced with a number of fmall holes, be interpofed between the gold Probe and the Sciatic Nerves, the Legs will not be convulfed. But, if the Paper be wetted, although it is not perforated, the Legs will be convulfed. After preparing a Frog, as In laft Experiment, and lay- ing the Spine on one glafs, and the Legs on another, if the Zinc be Jald on a third glafs, and the gold Probe applied to it and to the Sciatic Nerves, the Legs will not be convul- fed. 8. If the Spine and hind Legs, connedled by the Sciatic Nerves, are all laid on the fame plate of Zinc, fupported by glafs, the Legs are not convulfed on touching the Zinc C with 22 0 B S ERVATIONS on the •with the gold Probe held in the right hand, although the left hand is applied to the Legs. 9. If feveral Frogs, prepared as above defcribed, are laid upon glafs, in a flraight line touching each other, and that the firil Frog is fupported on Zinc, and the lafl upon Gold ], if one end of a brafs wire is applied to the Zinc, and the other end of it to the Gold ; the Mufcles of all the Frogs will be convulfed. The event is the fame, although a ftick of fealing-wax be interpofed between the hand of the Operator and the brafs wire: that is, although the Frog Avith the Metals be infulated. 10. When Frogs are prepared as in lafl Experiment, and the Spine of the firft of them laid on Zinc, and the lafl fup- ported by the left hand of the Operator, if with a gold Probe, held in his right hand, he touches the Zinc, the Mufcles of all the Frogs will be convulfed. But if the hind Legs, as well as the Spine, of the firfi: Frog be laid on the Zinc, the Mufcles of that Frog will not be convulfed. 11. After a Frog was prepared as before defcribed, I cut the Sciatic Nerves where they are about to enter the Thighs, and laid their cut ends in contad with the Mufcles, and NERFOUS SrSTEM. 23 and then touched the Zinc and Nerves with a gold Probe, without exciting convulfions in the Thighs or Legs. 12. After cutting the Sciatic Nerves, I tied together their divided parts, and then touched the Zinc and Nerves above the Ligature, with the Gold, without finding that the Legs were convulfed, when the Zinc fupporting the Spine was laid on one glafs and the Legs on another : but when the Metals and parts of the Frog were laid on a wet Table, the Mufcles of the Leg were convulfed. 13. When the Sciatic Nerves have been cut and rejoin- ed by Ligature, if while the Gold is, with one hand, ap- plied to the Zinc and Nerves, above the Ligature, the other hand touches the Feet, the Legs are convulfed. 14. If the two hind Legs of a Frog are feparated from each other, and their Sciatic Nerves afterwards tied to each other ; if one of the Legs be laid on Zinc fupported by glafs, and the other Leg on glafs, when, with one hand, the Toes of one of the Legs are touched, whilfl with the other hand a gold Probe is applied to the Zinc and Nerve of the Leg which it fupports, this Leg only will be'^convul- fed. But if the gold Probe touching the Zinc be applied C 2 to 24 0 B S E R VA T 10 NS on the to the Nerve of the mofl diftant Leg, both Legs will be convulfed. 15. I FOUND it was not neceflary, in order to excite convullions, that either of the Metals Ihould be in contad: with the living Nerve or living Flefh of the Frog; for if, after feparating from each other the hind Legs of a Frog, and cutting tranfverfely the upper part of their Sciatic Nerves, I laid a piece of putrid or boiled beef between their Sciatic Nerves, and two other pieces of putrid or boiled beef between their Toes and a plate of Zinc ; if, with the point of a gold Probe, the fide of which was ap- plied to the piece of beef placed between the Sciatic Nerves, I touched the Zinc, both Legs were convulfed. 16. In like manner, when I placed alternately, in a flraight line, a number of dead and living Frogs touching each other, and in the living Frogs cut, at their Pelvis, all the parts but the Sciatic Nerves 3 if, with my left hand I touched a dead Frog at one end of the line, and with a gold Probe, held in my right hand, I touched a plate of Zinc, on which a dead Frog was laid at the other end of the line or chain of Frogs, the Mufcles of all the living Frogs were convulfed. 17. When NERVOUS SrSTEM. 2.5 17. When a chain of living and dead Frogs was formed, as in the two lafl Experiments, but without cutting at their Pelvis all the parts but the Nerves ; on applying the gold to the Zinc, convulfions of the Mufcles were not excited. 18. It has been found, that, If a plate of Zinc is applied to the upper part of the point of the Tongue, and a plate of Silver to its under part, on bringing the two Metals in- to conta6t with each other, a pungent difagreeable feeling, which It Is difficult to defcribe, is produced In the point of the Tongue. And If a plate of Zinc Is placed between the upper lip and the gums, and a plate of gold applied to the upper or under part of the Tongue, on bringing thefe two Metals Into contadi with each other, the perfbn imagines that he fees a flafla of lightning, which, however, a by- ftander In a dark room does not perceive^ and the perfon performing the Experiment perceives the flafh, though he Is hoodwinked. It has been alleged, that the Flafli happens before the two Metals touch each other, and is repeated on feparating them; but thefe fadis appear to me very doubtful, as I do not find that a Flafh is produced when a piece of Cam- bric-paper, In which a number of holes is pierced with 2 ai 26 OBSERVATIONS on the a pin, is interpofed between the Zinc and Silver, although the Paper does not in thicknefs exceed tjo o- P^^'t of an inch. After performing this Experiment repeatedly, I con- flantly felt a pain in my upper jaw at the place to which the Zinc had been applied, which continued for an hour or more : And in one Experiment after I had applied a blunt Probe of Zinc to the Septum Narium, and repeatedly touched with it a Crown piece of Silver applied to the Tongue, and thereby produced the appearance of a Flafh, feveral drops of Blood fell from that Noflril; and Dr Fowler, after making fuch an Experiment on his Ears, obferved a fimilar effed: *. I HAVE farther obferved, that although the previous ap- plication of a fecond plate of Silver to one half of the plate of Zinc, does not prevent the Flafh when the other half of the plate of Zinc, touching the Tongue, is. brought into con- tadt with the firfl piece of Silver placed between the lip and the gum ; yet if the Zinc and Silver are in the firfl place applied to each other, then placed between the lip and gum, * See Dr Fowler's Book, p. 85. NERVOUS SrSTEM. 27 gum, and, after this, touched with the Tongue, there is no appearance of a Flafh, although fome degree of pungency and a difagreeable fenfiition is perceived by the Tongue : and a mixed mafs, compofed of one part of Zinc and two parts of Quickfilver, or a mafs compofed of three parts of Zinc and one of Silver, incorporated in a furnace, have not the effedl, when they are applied to Nerves, of exciting convullions of the Mufcles in which the Nerves terminate. I HAVE alfo found, that two thick pieces of raw or boiled flefh, one between the Zinc and Tongue, and the other be- tween the Silver and Tongue, do not prevent the dif- agreeable pungent fenfation when the two Metals touch : and, in like nnanner, that the interpofition of two pieces of flefh between the Zinc and Tongue, and between the Sil- ver and the upper Lip, does not prevent the appearance of a Flafh, on bringing the two Metals into contact. 19. I PUT a very thick plate of Zinc into a velfel with water, and placed, near to it, in the water, the under part of the Spine and the hind Legs of a Frog, after cutting all the parts at the Pelvis except the Sciatic Nerves. 1 then touched the Zinc with a gold Probe, and found, that, when I touched that part of the Zinc which was above the water, 3 the- -28 OB S ERVAT IONS on the the Legs of the Frog were not afFeded ; but when I touch- ed that part of the Zinc which was below the furface of the water, the Legs of the Frog were convulfed *. I NEXT put into the water one of the hind Legs of a dead Frog, and its other Leg into an adjoining veflel with water. Into the oppofite fide of the fecond vefTel, I put one of the hind Legs of a living Frog, in which all the parts at the Pelvis, except the Sciatic Nerves, were cut ; and into a third glafs veflel with water, I put its other Leg. When I now touched that part of the Zinc, which was below the furface of the water with a gold Probe, the Legs were not convulfed ; but, if I, at the fame time, dipped the finger of my other hand into the water contained in the third vefl^el, they were convulfed: when, inftead of my finger, I dipped into the water a flick of fealing-wax, held in my other hand, the Legs were not convulfed. • After reading to the Royal Society, on the 3d of June, an account of this Experiment, which I had made in the beginning of May, I found, from an in- genious publication of my PupU Dr Fowler, which I received that evening, that the fame Experiment had been performed by him. NERFOUS SrsTEM. 29 I FOUND, by the three following Experiments, that the Mufcles are convulfed, whether the Influence, produced by the application of the Metals, pafles upwards or down- wards along the Nerves. 20. I CUT four living Frogs tranfverfely at the middle part of their Spines, and threw away the fore parts of their Bodies and their Abdominal Vifcera. I NEXT cut, at their Pelves all the Parts but the Sciatic Nerves 3 and at their Knees, I cut all the Parts but the Crural Nerves j and, in all of them, I cut afunder the joining of the two hind Legs at their Ofla Pubis. I then laid the Legs of all of them In a flraight line, fup- ported on different Glafs Veflels inverted, in fuch a man- ner that the Foot of one Frog touched the Foot of the next to It. Having then placed a Plate of Zinc under the Foot of the firft Frog, and holding In my left hand the Foot of the fourth or lafl Frog, I touched the Zinc with a gold Probe which I held In my right hand} and found that all the Mufcles of the Loins, Thighs and Legs of the four Frogs were convulfed, D, zi. Whzn. .3Q OBSER VA TIO NS on the 21. When I placed the two Frogs in the middle, with their Spines contiguous to each other, and the Feet of both touching the Spines of the other two Frogs fonning the Extremities of the Chain, and of courfe the Feet of one of thefe refting on the Zinc, and the Feet of the other fup- ported by my left hand : On touching the Zinc with the gold Probe held in my right hand, all the Mufcles of the Frogs were, as before, convxilfed. 22. When I now turned afide the right Legs of all the Frogs, fo that they did not form a Chain by touching the next Frogs ; the right Legs were not convulfed. It is evident, that in whatever diredion we fuppofe the influence to have pafled in its Circle, it muft, in Experi- ment 20th, have pafled up one Leg and down the other in the fame Frog: And, in Experiment 2ifl;, if it pafl'ed from one end of the Chain to the other end of it, it muil have pafl^ed upwards in two of the Frogs, and downwards in the other two ; or if the influence pafl~ed from the two ends of the Chain towards its middle, where the Spines of the two middlemofl: Frogs were contiguous, it mufl: have paflTed upwards in all of them. 23. When NERVOUS SrsTEM, 31 23. When after cutting four living Frogs tranfverfely at the middle of their Spines, but without cutting at their Pelves all the Parts but the Sciatic Nerves, I placed the hind Parts of them in a Chain, as in Experiments 20th, 21ft and 2 2d, the Mufcles were not convulfed on applying the Gold to the Zinc. I NEXT found, that after placing in contad with each other the feveral Mufcles which had been cut tranfverfely in Experiments 20th, 21 ft and 2 2d, allowing the Nerves to remain undivided, the mufcles were not convulfed when I touched the Plate of Zinc with the gold Probe held in my fight hand, although I touched the other end of the Chain of Frogs with my left hand. The reafon why the Mufcles were convulfed in Experi- ments 20th, 2ift and 22d, and not in Experiment 23d, evi- dently is, that in the former, the influence was concentra- ted in the Nerve, in the latter the influence was difEifed 3 that is, was in part conveyed by other Organs, as well as by the Trunks of the Nerves.. 24. After finding that I could readily excite Convul- fions in the hind Legs of a Frog, without cutting it, by D 2- laying 32 OBSERVATIONS on the laying its Back on a Plate of Zinc, and introducing a gold Probe within its Inteftinum Redum and touching the Zinc with the fide of the Probe, I produced two or three hundred Convullions, fucceeding each other quickly, and obferved that its Legs were, by thefe means, fo much weakened, that it could not jump, and crawled with diffi- culty, but in a few minutes it recovered nearly the full force of its Mufcles. In other Frogs I palTed a gold Wire between their Sci- atic Nerves and Os Sacrum, and twilled together the two ends of the Wire over the Backs of the Animals. I then put them into a Zinc VefTel filled with Water, or into a Glafs VefTel filled with Water, in the bottom of which I laid a large Plate of Zinc: So that every time the Ani- mals by moving feparated the Gold from the Zinc, and again brought them into contadf, their hind Legs were convulfed. I allowed them to remain three or four days in this fituation, and found that their Limbs were weak- ened confiderably, but not exhaufled of their Power of Motion 3 and, after removing the gold Wire, the Limbs by degrees recovered their flrength. NERl^OUS SrSTEM. 33 I MADE the fame Experiment on thofe Frogs in which I had, fix weeks before, cut out, from behind, all that part of their Spinal Marrow which is covered by the fix under- moft Vertebrae, and found, feveral days after the Frogs had been fubjeded to the Experiment, that, by pinching their Sciatic and Femoral Nerves, and lllll more readily by the application of the Gold and Zinc, weak convulfions of the Mufcles were excited. 25. After Frogs were prepared as above defcrlbed, by cutting their Spines tranfverfely, and then all the parts of their Pelves, except their Sciatic Nerves, I found that flight Eledlrlcal Shocks, or a Leyden Phial difcharged diredlly through the Limbs of a Frog, or indlred:ly by the medium of water, produced convulfions in their Mufcles, exadly refembling thofe excited by the Metals. And when, after moderate Electrical Shocks had been pafi^d repeatedly through their Legs, the Metals were applied to their Nerves, in the manner before mentioned, the Mufcles were convulfed. I found, llkewife, that after cutting the Nerves tranfverfely, and tying them together, Eledrical Shocks were condudted by the Nerves, and occafioned convulfions of the Mufcles. When 34 OBSERVATIONS on the When I had killed Frogs, by difcharging' through them, from their foreheads to their hind feet, large Ley den Phials highly charged, I found their Nerves or Mufcles, or both, fo much deranged, that feeble convullions only could be excited by pinching the Nerves, or by applying the Me- tals to them. SUMMARY NERVOUS srSTEM, ^5 SUMMARY OF FAGTS proved by the foregoing EXPERIMENTS. On jjfvlewing the foregoing ExperinienCs, we iliall find the following Fadls fully proved. 1. On forming a Circle by means of the parts of a living Animal and of two different metallic Bodies, efpecially Gold and Zinc, in contad with each other, if a Nerve makes part of the Circle, the Mufcles in which the Nerve terminates are convulfed. 2. Although the Nerve ma;king part of fuch a Circle has been cut tranfverfely, yet, if the divided parts of the Nerve are laid in contad: with each other, or tied together, the Mufcles, in which it naturally terminates, are convul- fed. ■ - 1 3' If D 6 OBSERVATIONS on the 3. If die Metals, compofing parts of the Circle, are kept fleadlly in conta6l with each other, the convullions of the Mufcles ceafe. But, if they are feparated from each other and again rejoined, the convulfions are repeated. 4. The effeds are the fame, although the dead parts of an Animal or pure water make parts of the Circle. 5. Although the dead parts of an Animal, making part of fuch a Circle, are in contact with the Metals, the effeds. are the fame. 6. A MUSCLE making part of fuch a Circle may be con- vulfed whilfl the matter put in motion is pafling in the di- redion from the Mufcle to the Nerve. 7. The Mufcle may be convulfed although it makes no part of the Circle in which the matter put in motion pafles, as appears from comparing Experiment 5th with Experi- ments 13th and 14th. From Experiment 1.3th, it appears, that the Fluid put in Motion by the Metals pafTes readily along a Nerve, after it has been, cut, providing the divided Parts of it are brought into contad with each other. Yet in Experiment 14th, in which the left hand of the Opera- A tor NERVOUS SrSTEM, 37 tor was not applied to the Foot of the Frog, the Mufcles in which the Nerve, lower than the Ligature, terminated, were not convulfed, becaufe the Fluid put in motion did not de- fcend lower than the place at which the gold Probe touch- ed the Nerve above the Ligature. We may therefore pre- fume that when a Nerve which has not been cut, as in Ex- periment 5th, is touched with the gold Probe, the Fluid put in motion does not pafs lower in the Nerve than the place of the Probe. Hence we perceive the error of thofe who fuppofe that the moifture on the furface of the Nerve condudls the Fluid put in motion to the Mufcles, and that their adlion is In confequence of the dlredl operation of^ this Fluid upon their Fibres. 8. The effedis are the fame when the Animal and the Metals are infulated, by being placed on Glafs, whilft Seal- ing-wax is interpofed between the hand of the Operator and the Metals. 9. If any part of the Circle is compofed of Sealing-wax or Glafs, the Mufcles are not convulfed. 10. Convulsions are not excited unlefs the Metals are in contadl with each other j and unlefs both Metals are alfa in contad: with the Animal Subflances or the Water making part of the Circle. E RE- jjg Q B S ERFJTIO NS Qit the RESEMBLANCE of the FLUID put in MOTION by THE FOREGOING EXPERIMENTS TO THE ELECTRI- CAL FLUID. The Fluid fet in motion by the application of the Metals to each other, and to Animal Bodies or to Water, agrees with or refembles the Eledrical Fluid in the following re- fpedts. Like the Eledtrical Fluid, it communicates the fenfe of pungency to the Tongue. Like the Eledtrical Fluid, it is conveyed readily by Wa- ter, Blood, the Bodies of Animals, the Metals ^ and Is ar- relied in its courfe by Glafs, Sealing- Wax, Sifr. It pafTes, with fimilar rapidity, through the Bodies of Animals. Like NERVOUS SrSTEM. 39. Like the Ele6lrical Fluid, it excites the adlivity of the Vellels of a living Animal, as the Pain it gives and Hemor- rhagy it produces feem to prove. Hence perhaps it might be employed with advantage in Amenorrhoea. It excites Convulfions of the Mufcles in the fame man- ner, and with the fame effedls as Eledlricity. When the Metals and Animal are kept fteadily in con- ta<5t with each other, the Convulfions ceafe, or an Equili- brium feems to be produced, as after difcharging a Leyden Phial. E 2 Tim. 40 OBS ERVATIONS on the The nervous FLUID or ENERGY not the same WITH THE ELECTRICAL nor with the FLUID put IN motion by the foregoing EXPERIMENTS. That the Nervous Fluid is the fame with the Eledrlcal, or with the Fluid which is put iii motion by the foregoing Experiments, is, I apprehend, difproved by the following circumllances. I. Without Hating the difficulty there is in conceiving how the Eledlrical Fluid can be accumulated by or con- fined within our Nervous Syftem, we may obferve that where the Eleclrical Fluid, or Fluid refembling that put in motion by the foregoing Experiments, is accumulated by an Animal, fuch as the Torpedo or Gymnotus, a proper apparatus is given to the Animal, by means of which it is enabled to colled and to difcharge this Fluid. 2. The NERFOUS SrSTEM. 41 2. The Nervous Power is excited by chemical or by me- chanical Stimuli J and, on the other hand, is deftroyed by Opium and other Poifons, which cannot be imagined to adt on the Eledrical Fluid. 3. I HAVE, I apprehend, refuted the theory of Do6lors Galvani, Valli and others, which fuppofes that the Nerve is eledrified plus and the Mufcle mi7ius, refembling the Leyden Phial, by fhewing that the Mufcles are convul- fed where there is no communication between them and the Metals, but by the medium of the Nerve ^ or when the Me- tals are applied to different parts of the Nerve alone, with- out touching the Mufcles which are convulfed, and when the Mufcle which is convulfed makes no part of the Circle in which the Matter that is put in motion pafles. 4. I HAVE proved, that the Mufcles are convulfed whilft the current of the Eledlrical Matter is pafling from them and from the fmaller Branches of the Nerves into their Trunks ; and as a Mufcle is never thrown into Ad:ion by the Nervous Energy, except when this palles from the Trunk of the Nerve into its Branches, and from thefe into the Mufcle, it appears that when, in thefe Experiments, the Mufcles were convulfed, the Nervous and the Eledrical Fluids 42 OBSERVATIONS on the Fluids were moving in oppofite Diredions ; from which we may infer, that, in their Nature, they differ eflentially from each other. 5. The Nervous Energy is flopped by a tight Ligature or by the tranfverfe Incifion of a Nerve, although its di- vided Parts are thereafter placed in contad with each o- ther 5 whereas the Eledtrical Fluid or the Fluid excited by the Metals, pafles readily, downwards or upwards, along a Nerve which has been tied or cut. 6. After the Limb of a living Animal has been amputa- ted, frequent Convulfions of the fame Mufcles may be ex- cited by applying Mechanical or Chemical Stimuli to its Nerves ; whereas Eledrical Matter difcharges itfelf fuddenly. Hence I conclude, I. That the Fluid, which, on the application of Metal- line Bodies to Animals, occafions Convulfions of their Muf- cles, is eledrical, or refembles greatly the Eledrical Fluid. 2. That NERFOUS SrStEM. 43 2. That this Fluid does not operate dlredly on the Mufcular Fibres, but merely by the Medium of their Nerves. 3. That this Fluid and the Nervous Fluid or Energy are not the fame, but differ effentially in their Nature. 4. That this Fluid ads merely as a Stimulus to the Nervous Fluid or Energy. 5. That thefe Experiments have merely fhown a new mode of exciting the Nervous Fluid or Energy, without throwing any farther or dired Light on the nature of this Fluid or Energy. FINIS* COUNTWAY LIBRARY OF MEDICINE QP 331 RARE BOOKS DEPARTMENT C^.;/^ ^/^.j, sy. M,^/'' • -^^1 'f^^f^ 1/^f. ■/^tf