EXPERIMENTS ON THE NERVOUS SYSTEM, 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 AND 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 AND COMPANY, FOR BELL & BRADFUTE, AND T. DUNCAN; AND J. JOHNSON, LONDON.
M.DCC.XCIII.
CONTENTS.
[]- INTRODUCTION, Page 1
- Obſervations on the Circulating and Nervous Syſtems of Frogs, Page 6
- Experiments with Opium, Page 9
- Corollaries from the above Facts and Experiments, Page 12
- Summary of Experiments made on Animals with Me⯑talline Subſtances, Page 17
- Summary of Facts proved by the foregoing Experi⯑ments, Page 35
- Reſemblance of the Fluid put in Motion by the fore⯑going Experiments to the Electrical Fluid, Page 38
- The Nervous Fluid or Energy not the ſame with the Electrical, nor with the Fluid put in Motion by the foregoing Experiments, Page 40
- General Concluſions, Page 42
INTRODUCTION.
[]WHEN, in November laſt, I began to make Experi⯑ments on Animal Electricity, of which I read ſome account to the Royal Society on the 3d of December; I was not only much hurried with buſineſs, but could not procure a ſufficient number of Frogs for the purpoſe. Du⯑ring the laſt winter and ſpring, I proſecuted the ſubject more fully and with greater attention; and, on the third day of June, I read a ſecond paper to the Royal Society, to which I have, ſince that time, made additions. I ſhall now ſtate a ſummary of the chief circumſtances I have obſerved, with a few Remarks.
OBSERVATIONS ON THE CIRCULATING AND NER⯑VOUS SYSTEMS OF FROGS.
[6]As my Experiments with Opium, as well as thoſe on Animal Electricity, have been performed on Frogs chiefly; I ſhall premiſe ſome obſervations on their Circulating and Nervous Syſtems.
THEIR Heart conſiſts of one Auricle and one Ventricle only, their Aorta ſupplying their Air Veſicles or Lungs, as well as all their other Organs; and, of courſe, their Venae Cavae return the Blood from all parts to the Heart. The Ventricle of their Heart contracts about ſixty times in a minute; and the purple colour of the Blood which is ſeen within it, diſappears after each contraction, or the Blood is entirely expelled by its contraction. 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 contracts its [7]Legs when the Toes are hurt, though not with ſufficient force to move its Body from the place where it is laid.
THEIR Encephalon conſiſts of Brain and Cerebellum, each of which, on its upper part, is divided into two He⯑miſpheres; 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 conſiſt of two Cords. There are nine true Vertebrae; and at the ſixth of theſe, the Spinal Marrow terminates in the Cauda Equina. The Sciatic Nerves are formed by three pairs of Nerves, ſent out below the ſeventh, eighth and ninth Vertebrae, and by one pair from the Os Sacrum. A Nerve, reſembling our great Sympathetic Nerve, paſſes downwards from the Abdomen into the Pel⯑vis.
Two days after cutting off the Head of a Frog at its joining with the firſt Vertebra, I found it ſitting with its Legs drawn up, in their uſual poſture; and when its Toes were hurt, it jumped with very conſiderable force. Its Heart likewiſe continued to beat about forty times in a mi⯑nute, and ſo ſtrongly as to empty itſelf and circulate the Blood.
[8]IN ſeveral Frogs, after cutting off the back part of the ſix undermoſt true Vertebrae, I took out all that part of the Spinal Marrow with the Cauda Equina which they cover. The lower Extremities were rendered inſenſible to common injuries, and lay motionleſs; yet the Frogs lived ſeveral months thereafter, and the wounded parts of their Backs cicatriſed; and the Bones of their Legs, which I fractured, were re-united, the Blood circulating freely in their Veſſels.
IT is univerſally known, that if, after amputating the Limb of a warm blooded Animal, we repeatedly irritate the Nerves which terminate in Muſcles, repeated Convul⯑ſions of the Muſcles are for ſome time produced; and that in Frogs, and other cold blooded Animals, the Nerves retain this power ſtill longer.
BUT it has been commonly ſuppoſed, that, after irri⯑tating the Nerve a given number of times, the effect ceaſes, Authors conceiving that there is lodged in the Nerve ſome fluid, or other energy which is exhauſted by repeated ex⯑ploſions. Inſtead of this, I have found that the time the Nerves preſerve their power is the ſame, whether we irritate them or not; or that their energy is not ex⯑hauſted [9]by irritation, unleſs the irritation be ſuch as ſen⯑ſibly 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 lowermoſt Vertebrae, and then injected, from the one hole to the other, a ſmall ſyringe full of water, in five ounces of which one ounce of Opium had been infuſed for three days. The infuſion, by this means brought into contact with the whole ſurface of the Encephalon and Spi⯑nal Marrow, produced almoſt inſtantly univerſal convul⯑ſions; and, in leſs 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; and ſo feebly, that it could not entirely expel the Blood. When [10]half an hour thereafter, the Sciatic Nerves were pinched, a ſlight tremor only was excited in the Muſcles of the Leg; and Animal Electricity produced but feeble twitchings of the Muſcles.
THE infuſion of Opium, injected in the ſame manner in Rabbits and in a Pig, produced ſimilar effects.
I HAD long ago* obſerved, that an infuſion of Opium, poured into the Cavity of the Abdomen of a Frog, after cutting out its Heart, occaſioned, in a few minutes, con⯑vulſions of its hind Legs. I have ſince found, that, after cutting off the Head, and cutting out the Heart of a Frog, its hind Legs are conſiderably weakened by pouring an in⯑fuſion of Opium into the Cavity of its Abdomen.
ALTHOUGH an infuſion of Opium poured into the Auricle and Ventricle of the Heart of a Frog, inſtantly renders that Organ incapable of contraction, and, even after the Aorta has been previouſly cut, occaſions convulſions of the Legs, yet I have not found that by Opium applied to the Brain, the Spinal Marrow, the Heart, or Abdominal Viſcera, the Muſcles of the Legs were ſo entirely killed as not to per⯑form [11]ſome motion when their Nerves were pinched, or when they were acted on by Animal Electricity.
AFTER taking out the lower half of the Spinal Marrow, and likewiſe cutting tranſverſely all the parts at the Pelvis, except the Crural Arteries and Veins and Lymphatics, which probably accompany them, I found that an infuſion of Opium, applied to the Skin and Muſcles of the Legs, affected the ſuperior parts of the Body*: more probably, in my opinion, by abſorption, than through any minute remanent branches of the Nerves, eſpecially as I do not find, on laying the Veſſels ſo prepared over a gold probe, and touching with it Zinc laid under the Spine, that con⯑vulſions of the Legs can be excited. At the ſame time, the quantity of Opium abſorbed is ſo ſmall, that I could not diſtinguiſh its ſmell or taſte in the Blood; nor did I find theſe diſtinguiſhable, in other Experiments, in which the Frogs were violently convulſed after applying the infuſion to the ſurface of their Skin.
ANIMAL Electricity or different metals applied to the Head of a Frog, or to any part of its Spine above its ſixth Vertebra, do not occaſion convulſions of its hind Legs.
COROLLARIES FROM THE ABOVE FACTS AND EX⯑PERIMENTS.
[12]FROM the above Facts and Experiments, it appears,
- 1. THAT the Frog, after its Head is cut off, feels pain, and, in conſequence of feeling, moves its Body and Limbs.
- 2. As the Nerves of the hind Legs are not affected by Animal Electricity, unleſs it be applied lower than the fifth Vertebra, theſe Nerves do not ſeem to be derived ſolely or chiefly from the Brain or Cerebellum.
- 3. As Opium, after the Circulation ceaſes, affects Organs diſtant from thoſe to which it is applied, it is beyond doubt, that the latter ſuffer in conſequence 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 [13]Nerves does not, in this Animal, depend entirely on the connection of Nerves within the Head.
- 5. As, after cutting off the Head, this Animal is ſuſcep⯑tible of pain, and, in conſequence of that, performs volun⯑tary motion, it appears that, in it, the Brain is not the ſole ſeat of the Senſorium Commune.
- 6. SEVERAL weeks after I had taken out the lowermoſt half of the Spinal Marrow, and with it the Cauda Equina, I daily applied, for four days running, Animal Electricity to the Sciatic Nerves, by paſſing a gold Probe between them and the Os Sacrum, and excited ſeveral hundreds of convulſions of the Thighs and Legs, and yet found that, on laying bare the Femoral Nerves, and pinching them, the Muſcles were ſlightly convulſed.
HENCE, I apprehend, additional force is given to an opinion I ventured many years ago to propoſe*, 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 ſuch as to furniſh it, or that the ſtructure of each Nerve is ſimilar to that of the Brain.
[14]7. FROM the above Experiments, it appears probable, in the higheſt degree, that Opium may be abſorbed in ſuch quantity as to produce fatal ſymptoms.
8. THE following circumſtances concur in rendering in⯑admiſſible an opinion lately propoſed by M. FONTANA, that Poiſons operate by changes they produce on the maſs of Blood, or on ſome unknown principle connected with the Blood.
a. IF his opinion was juſt, Poiſon introduced into a Vein of the extremities, ſo as to be in contact with this unknown principle, ſhould operate as quickly, and in the ſame man⯑ner as when the Poiſon is mixed with the Blood near the Heart, which he admits is not the caſe*.
b. CUTTING the Spinal Marrow in Frogs, before apply⯑ing the Poiſon of the Viper to their Legs, prevents it from killing them†; which ſhould not happen, if the Poiſon act⯑ed on the Blood alone.
[15]c. HE acknowledges that an Animal bit in its Leg by a Viper, inſtantaneouſly feels acute pain*; and it, in like manner, feels inſtantly great uneaſineſs when the Poiſon is mixed with its Blood†. We know for certain, that, through the medium of the Nerves, we are inſtantly ren⯑dered ſenſible of injury done to the moſt diſtant parts of our Bodies.
ARE we not, therefore, in the laſt mentioned Experi⯑ment, to conclude, that the uneaſineſs was produced be⯑cauſe the Poiſon acted upon the Nerves of the Veſſels?
d. IN like manner, Animals were convulſed as ſoon as they were wounded, or received the Poiſon into a Blood⯑veſſel; and long before the Blood could have reached the Muſcles in action‡.
e. As ſoon as the diſtilled Water of Lauro-ceraſus was poured into the Stomach of a Pigeon, it was convulſed, and [16]died inſtantly*, that is, before the Poiſon could have entered the Maſs of Blood.
f. MANY years ago, I found, after cutting the Venae Cavae and Aorta of a Frog, that a watery ſolution of Opium poured into the Heart, occaſioned, in a few minutes, con⯑vulſions in its Legs; and, after cutting out the Heart, that the Opium poured into the Cavity of the Abdomen affect⯑ed the Legs in like manner; although, in theſe Experi⯑ments, the Circulation was not only interrupted, but the greater part of the Blood evacuated.
I THEREFORE then concluded†, and now conclude, that Opium and other Poiſons, even after they are mixed with the Maſs of Blood, produce their fatal effects, chiefly and almoſt ſolely, by acting on the Nerves of the Heart and Vaſcular Syſtem, and, through theſe, affecting the whole of the Nervous Syſtem.
SUMMARY OF EXPERIMENTS MADE ON ANIMALS WITH METALLINE SUBSTANCES.
[17]I SHALL now proceed to ſtate the ſeveral circumſtan⯑ces I have obſerved, in my Experiments, which more directly lead us to judge of the Nature and Cauſe of Animal Electricity.
1. WHEN two Plates of different Metalline Subſtances, particularly of Zinc and Gold, between which a living Frog is placed, are brought into contact with each other, thoſe Muſcles, which are farther from the Brain and Spinal Mar⯑row than the Metals, are convulſed: and this effect follows, although the Animal and Metals are placed on an inverted glaſs jar, and that a ſtick of ſealing wax is interpoſed be⯑tween the hand of the Operator and the Metals; that is, although the Animal, with the Metals, be inſulated.
[18]I HAVE further obſerved, that the Metals, diſpoſed as above deſcribed, excite convulſions in the Legs, after all the parts of the Frog have been divided tranſverſely at the Pelvis, providing only that they are, thereafter, laid in contact with each other.
2. WHEN all the parts of a living Frog, except the large Nerves called Sciatic, are cut tranſverſely at the Pelvis, and the fore part of the Animal is laid on a plate of Zinc, ſupported by glaſs, and the hind Legs on glaſs; if a gold Probe be applied ſo as to touch the Zinc and one of the Legs; or a piece of Metal put under one of the Legs; the Muſcles of both Legs will be convulſed.
THE event is the ſame, after the Body of the Frog has been cut tranſverſely about the middle of the Spine: or when the Legs are laid on the Zinc and the Spine on Glaſs.
IF a piece of perforated dry Paper is placed between the gold Probe and the Muſcles, there will be no convulſions; but wet Paper interpoſed does not prevent the convulſions.
ON ſeparating the gold Probe from the Muſcles there are no convulſions.
[19]3. IF, after the Animal and Metals are placed as above deſcribed, the joining of the two Legs at the Oſſa Pubis is cut, that Leg only will be convulſed with which the gold is in contact.
4. THE Spine of the Frog with the Zinc being placed on one glaſs, and the Legs on another glaſs, if the gold, ſup⯑ported by one hand, which we ſhall call the Right Hand, be applied to the Zinc alone, and not to the Legs, theſe are not convulſed. But if the Operator applies his left hand to the Legs, or if a byſtander, communicating with the Operator by the medium of the floor only, touches them, they are convulſed. If a ſtick of ſealing-wax be interpoſed between his right hand and the gold, or between his left hand and the Legs; or, if the byſtander, touching the Legs, is inſulated, by ſtanding on a ſtool ſupported by glaſs feet, the Legs will not be convulſed. If the inſu⯑lated byſtander touches the Legs with one hand, and the Operator with his other hand, the Legs are immediately convulſed.
5. AFTER cutting the Spine tranſverſely under the fifth Vertebra, and all the parts of the Pelvis, except the Sciatic Nerves, and laying the Spine on Zinc ſupported by glaſs, [20]and the Legs on glaſs; if gold be applied to the Zinc, and then to one of the Sciatic Nerves, both Legs, if they have not been ſeparated from each other at the Oſſa Pubis, will be convulſed*. And this happens although a ſtick of ſeal⯑ing-wax be interpoſed between the hand of the Operator and the gold Probe, and although no Metalline Subſtance touches the Legs.
THIS Experiment ſucceeds after denuding the Sciatic Nerves for the length of an inch, and wiping them dry; and it continues to ſucceed for an hour or more, and till the Nerves are evidently diſcoloured and ſhrunk in their ſize. And, after that, although we wet the Nerves, their powers are not reſtored; ſhewing that the influence had been conveyed not by wetneſs on the ſurface of the Nerves, [21]but by the particular matter of which Nerves are com⯑poſed.
THE event is the ſame, 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 laſt Experiment, if a piece of thin dry Paper, pierced with a number of ſmall holes, be interpoſed between the gold Probe and the Sciatic Nerves, the Legs will not be convulſed. But, if the Paper be wetted, although it is not perforated, the Legs will be convulſed.
AFTER preparing a Frog, as in laſt Experiment, and lay⯑ing the Spine on one glaſs, and the Legs on another, if the Zinc be laid on a third glaſs, and the gold Probe applied to it and to the Sciatic Nerves, the Legs will not be convul⯑ſed.
8. IF the Spine and hind Legs, connected by the Sciatic Nerves, are all laid on the ſame plate of Zinc, ſupported by glaſs, the Legs are not convulſed on touching the Zinc [22]with the gold Probe held in the right hand, although the left hand is applied to the Legs.
9. IF ſeveral Frogs, prepared as above deſcribed, are laid upon glaſs, in a ſtraight line touching each other, and that the firſt Frog is ſupported on Zinc, and the laſt upon Gold; if one end of a braſs wire is applied to the Zinc, and the other end of it to the Gold; the Muſcles of all the Frogs will be convulſed. The event is the ſame, although a ſtick of ſealing-wax be interpoſed between the hand of the Operator and the braſs wire: that is, although the Frog with the Metals be inſulated.
10. WHEN Frogs are prepared as in laſt Experiment, and the Spine of the firſt of them laid on Zinc, and the laſt ſup⯑ported by the left hand of the Operator, if with a gold Probe, held in his right hand, he touches the Zinc, the Muſcles of all the Frogs will be convulſed. But if the hind Legs, as well as the Spine, of the firſt Frog be laid on the Zinc, the Muſcles of that Frog will not be convulſed.
11. AFTER a Frog was prepared as before deſcribed, I cut the Sciatic Nerves where they are about to enter the Thighs, and laid their cut ends in contact with the Muſcles, [23]and then touched the Zinc and Nerves with a gold Probe, without exciting convulſions 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 convulſed, when the Zinc ſupporting the Spine was laid on one glaſs and the Legs on another: but when the Metals and parts of the Frog were laid on a wet Table, the Muſcles of the Leg were convulſed.
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 convulſed.
14. IF the two hind Legs of a Frog are ſeparated from each other, and their Sciatic Nerves afterwards tied to each other; if one of the Legs be laid on Zinc ſupported by glaſs, and the other Leg on glaſs, when, with one hand, the Toes of one of the Legs are touched, whilſt with the other hand a gold Probe is applied to the Zinc and Nerve of the Leg which it ſupports, this Leg only will be convul⯑ſed. But if the gold Probe touching the Zinc be applied [24]to the Nerve of the moſt diſtant Leg, both Legs will be convulſed.
15. I FOUND it was not neceſſary, in order to excite convulſions, that either of the Metals ſhould be in contact with the living Nerve or living Fleſh of the Frog; for if, after ſeparating from each other the hind Legs of a Frog, and cutting tranſverſely 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 ſide of which was ap⯑plied to the piece of beef placed between the Sciatic Nerves, I touched the Zinc, both Legs were convulſed.
16. IN like manner, when I placed alternately, in a ſtraight 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; 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 Muſcles of all the living Frogs were convulſed.
[25]17. WHEN a chain of living and dead Frogs was formed, as in the two laſt Experiments, but without cutting at their Pelvis all the parts but the Nerves; on applying the gold to the Zinc, convulſions of the Muſcles 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 contact with each other, a pungent diſagreeable feeling, which it is difficult to deſcribe, 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 theſe two Metals into contact with each other, the perſon imagines that he ſees a flaſh of lightning, which, however, a by⯑ſtander in a dark room does not perceive; and the perſon performing the Experiment perceives the flaſh, though he is hoodwinked.
IT has been alleged, that the Flaſh happens before the two Metals touch each other, and is repeated on ſeparating them; but theſe facts appear to me very doubtful, as I do not find that a Flaſh is produced when a piece of Cam⯑bric-paper, in which a number of holes is pierced with [26]a pin, is interpoſed between the Zinc and Silver, although the Paper does not in thickneſs exceed 1/1500 part of an inch.
AFTER performing this Experiment repeatedly, I con⯑ſtantly 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 Flaſh, ſeveral drops of Blood fell from that Noſtril; and Dr FOWLER, after making ſuch an Experiment on his Ears, obſerved a ſimilar effect*.
I HAVE farther obſerved, that although the previous ap⯑plication of a ſecond plate of Silver to one half of the plate of Zinc, does not prevent the Flaſh when the other half of the plate of Zinc, touching the Tongue, is brought into con⯑tact with the firſt piece of Silver placed between the lip and the gum; yet if the Zinc and Silver are in the firſt place applied to each other, then placed between the lip and [27]gum, and, after this, touched with the Tongue, there is no appearance of a Flaſh, although ſome degree of pungency and a diſagreeable ſenſation is perceived by the Tongue: and a mixed maſs, compoſed of one part of Zinc and two parts of Quickſilver, or a maſs compoſed of three parts of Zinc and one of Silver, incorporated in a furnace, have not the effect, when they are applied to Nerves, of exciting convulſions of the Muſcles in which the Nerves terminate.
I HAVE alſo found, that two thick pieces of raw or boiled fleſh, one between the Zinc and Tongue, and the other be⯑tween the Silver and Tongue, do not prevent the diſ⯑agreeable pungent ſenſation when the two Metals touch: and, in like manner, that the interpoſition of two pieces of fleſh between the Zinc and Tongue, and between the Sil⯑ver and the upper Lip, does not prevent the appearance of a Flaſh, on bringing the two Metals into contact.
19. I PUT a very thick plate of Zinc into a veſſel 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. I then touched the Zinc with a gold Probe, and found, that, when I touched that part of the Zinc which was above the water, [28]the Legs of the Frog were not affected; but when I touch⯑ed that part of the Zinc which was below the ſurface of the water, the Legs of the Frog were convulſed*.
I NEXT put into the water one of the hind Legs of a dead Frog, and its other Leg into an adjoining veſſel with water. Into the oppoſite ſide of the ſecond veſſel, 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 glaſs veſſel with water, I put its other Leg. When I now touched that part of the Zinc, which was below the ſurface of the water with a gold Probe, the Legs were not convulſed; but, if I, at the ſame time, dipped the finger of my other hand into the water contained in the third veſſel, they were convulſed: when, inſtead of my finger, I dipped into the water a ſtick of ſealing-wax, held in my other hand, the Legs were not convulſed.
[29]I FOUND, by the three following Experiments, that the Muſcles are convulſed, whether the Influence, produced by the application of the Metals, paſſes upwards or down⯑wards along the Nerves.
20. I CUT four living Frogs tranſverſely at the middle part of their Spines, and threw away the fore parts of their Bodies and their Abdominal Viſcera.
I NEXT cut, at their Pelves all the Parts but the Sciatic Nerves; and at their Knees, I cut all the Parts but the Crural Nerves; and, in all of them, I cut aſunder the joining of the two hind Legs at their Oſſa Pubis. I then laid the Legs of all of them in a ſtraight line, ſup⯑ported on different Glaſs Veſſels inverted, in ſuch 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 firſt Frog, and holding in my left hand the Foot of the fourth or laſt Frog, I touched the Zinc with a gold Probe which I held in my right hand; and found that all the Muſcles of the Loins, Thighs and Legs of the four Frogs were convulſed.
[30]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 forming the Extremities of the Chain, and of courſe the Feet of one of theſe reſting on the Zinc, and the Feet of the other ſup⯑ported by my left hand: On touching the Zinc with the gold Probe held in my right hand, all the Muſcles of the Frogs were, as before, convulſed.
22. WHEN I now turned aſide the right Legs of all the Frogs, ſo that they did not form a Chain by touching the next Frogs; the right Legs were not convulſed.
IT is evident, that in whatever direction we ſuppoſe the influence to have paſſed in its Circle, it muſt, in Experi⯑ment 20th, have paſſed up one Leg and down the other in the ſame Frog: And, in Experiment 21ſt, if it paſſed from one end of the Chain to the other end of it, it muſt have paſſed upwards in two of the Frogs, and downwards in the other two; or if the influence paſſed from the two ends of the Chain towards its middle, where the Spines of the two middlemoſt Frogs were contiguous, it muſt have paſſed upwards in all of them.
[31]23. WHEN after cutting four living Frogs tranſverſely 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, 21ſt and 22d, the Muſcles were not convulſed on applying the Gold to the Zinc.
I NEXT found, that after placing in contact with each other the ſeveral Muſcles which had been cut tranſverſely in Experiments 20th, 21ſt and 22d, allowing the Nerves to remain undivided, the muſcles were not convulſed when I touched the Plate of Zinc with the gold Probe held in my right hand, although I touched the other end of the Chain of Frogs with my left hand.
THE reaſon why the Muſcles were convulſed in Experi⯑ments 20th, 21ſt 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 diſſuſed; 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⯑ſions in the hind Legs of a Frog, without cutting it, by [32]laying its Back on a Plate of Zinc, and introducing a gold Probe within its Inteſtinum Rectum and touching the Zinc with the ſide of the Probe, I produced two or three hundred Convulſions, ſucceeding each other quickly, and obſerved that its Legs were, by theſe means, ſo 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 Muſcles.
IN other Frogs I paſſed a gold Wire between their Sci⯑atic Nerves and Os Sacrum, and twiſted together the two ends of the Wire over the Backs of the Animals. I then put them into a Zinc Veſſel filled with Water, or into a Glaſs Veſſel filled with Water, in the bottom of which I laid a large Plate of Zinc: So that every time the Ani⯑mals by moving ſeparated the Gold from the Zinc, and again brought them into contact, their hind Legs were convulſed. I allowed them to remain three or four days in this ſituation, and found that their Limbs were weak⯑ened conſiderably, but not exhauſted of their Power of Motion; and, after removing the gold Wire, the Limbs by degrees recovered their ſtrength.
[33]I MADE the ſame Experiment on thoſe Frogs in which I had, ſix weeks before, cut out, from behind, all that part of their Spinal Marrow which is covered by the ſix under⯑moſt Vertebrae, and found, ſeveral days after the Frogs had been ſubjected to the Experiment, that, by pinching their Sciatic and Femoral Nerves, and ſtill more readily by the application of the Gold and Zinc, weak convulſions of the Muſcles were excited.
25. AFTER Frogs were prepared as above deſcribed, by cutting their Spines tranſverſely, and then all the parts of their Pelves, except their Sciatic Nerves, I found that ſlight Electrical Shocks, or a Leyden Phial diſcharged directly through the Limbs of a Frog, or indirectly by the medium of water, produced convulſions in their Muſcles, exactly reſembling thoſe excited by the Metals. And when, after moderate Electrical Shocks had been paſſed repeatedly through their Legs, the Metals were applied to their Nerves, in the manner before mentioned, the Muſcles were convulſed. I found, likewiſe, that after cutting the Nerves tranſverſely, and tying them together, Electrical Shocks were conducted by the Nerves, and occaſioned convulſions of the Muſcles.
[34]WHEN I had killed Frogs, by diſcharging through them, from their foreheads to their hind feet, large Leyden Phials highly charged, I found their Nerves or Muſcles, or both, ſo much deranged, that feeble convulſions only could be excited by pinching the Nerves, or by applying the Me⯑tals to them.
SUMMARY OF FACTS PROVED BY THE FOREGOING EXPERIMENTS.
[35]ON reviewing the foregoing Experiments, we ſhall find the following Facts fully proved.
- 1. ON forming a Circle by means of the parts of a living Animal and of two different metallic Bodies, eſpecially Gold and Zinc, in contact with each other, if a Nerve makes part of the Circle, the Muſcles in which the Nerve terminates are convulſed.
- 2. ALTHOUGH the Nerve making part of ſuch a Circle has been cut tranſverſely, yet, if the divided parts of the Nerve are laid in contact with each other, or tied together, the Muſcles, in which it naturally terminates, are convul⯑ſed.
- 3. IF the Metals, compoſing parts of the Circle, are kept ſteadily in contact with each other, the convulſions of the Muſcles ceaſe. But, if they are ſeparated from each other and again rejoined, the convulſions are repeated.
- 4. THE effects are the ſame, 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 ſuch a Circle, are in contact with the Metals, the effects are the ſame.
- 6. A MUSCLE making part of ſuch a Circle may be con⯑vulſed whilſt the matter put in motion is paſſing in the di⯑rection from the Muſcle to the Nerve.
- 7. THE Muſcle may be convulſed although it makes no part of the Circle in which the matter put in motion paſſes, as appears from comparing Experiment 5th with Experi⯑ments 13th and 14th. From Experiment 13th, it appears, that the Fluid put in Motion by the Metals paſſes readily along a Nerve, after it has been cut, providing the divided Parts of it are brought into contact with each other. Yet in Experiment 14th, in which the left hand of the Opera⯑tor [37]was not applied to the Foot of the Frog, the Muſcles in which the Nerve, lower than the Ligature, terminated, were not convulſed, becauſe the Fluid put in motion did not de⯑ſcend lower than the place at which the gold Probe touch⯑ed the Nerve above the Ligature. We may therefore pre⯑ſume 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 paſs lower in the Nerve than the place of the Probe. Hence we perceive the error of thoſe who ſuppoſe that the moiſture on the ſurface of the Nerve conducts the Fluid put in motion to the Muſcles, and that their action is in conſequence of the direct operation of this Fluid upon their Fibres.
- 8. THE effects are the ſame when the Animal and the Metals are inſulated, by being placed on Glaſs, whilſt Seal⯑ing-wax is interpoſed between the hand of the Operator and the Metals.
- 9. IF any part of the Circle is compoſed of Sealing-wax or Glaſs, the Muſcles are not convulſed.
- 10. CONVULSIONS are not excited unleſs the Metals are in contact with each other; and unleſs both Metals are alſo in contact with the Animal Subſtances or the Water making part of the Circle.
RESEMBLANCE OF THE FLUID PUT IN MOTION BY THE FOREGOING EXPERIMENTS TO THE ELECTRI⯑CAL FLUID.
[38]THE Fluid ſet in motion by the application of the Metals to each other, and to Animal Bodies or to Water, agrees with or reſembles the Electrical Fluid in the following re⯑ſpects.
LIKE the Electrical Fluid, it communicates the ſenſe of pungency to the Tongue.
LIKE the Electrical Fluid, it is conveyed readily by Wa⯑ter, Blood, the Bodies of Animals, the Metals; and is ar⯑reſted in its courſe by Glaſs, Sealing-Wax, &c.
IT paſſes, with ſimilar rapidity, through the Bodies of Animals.
[39]LIKE the Electrical Fluid, it excites the activity of the Veſſels of a living Animal, as the Pain it gives and Hemor⯑rhagy it produces ſeem to prove. Hence perhaps it might be employed with advantage in Amenorrhoea.
IT excites Convulſions of the Muſcles in the ſame man⯑ner, and with the ſame effects as Electricity.
WHEN the Metals and Animal are kept ſteadily in con⯑tact with each other, the Convulſions ceaſe, or an Equili⯑brium ſeems to be produced, as after diſcharging a Leyden Phial.
THE NERVOUS FLUID OR ENERGY NOT THE SAME WITH THE ELECTRICAL NOR WITH THE FLUID PUT IN MOTION BY THE FOREGOING EXPERIMENTS.
[40]THAT the Nervous Fluid is the ſame with the Electrical, or with the Fluid which is put in motion by the foregoing Experiments, is, I apprehend, diſproved by the following circumſtances.
- 1. WITHOUT ſtating the difficulty there is in conceiving how the Electrical Fluid can be accumulated by or con⯑fined within our Nervous Syſtem, we may obſerve that where the Electrical Fluid, or Fluid reſembling that put in motion by the foregoing Experiments, is accumulated by an Animal, ſuch as the Torpedo or Gymnotus, a proper apparatus is given to the Animal, by means of which it is enabled to collect and to diſcharge this Fluid.
- 2. THE Nervous Power is excited by chemical or by me⯑chanical Stimuli; and, on the other hand, is deſtroyed by Opium and other Poiſons, which cannot be imagined to act on the Electrical Fluid.
- 3. I HAVE, I apprehend, refuted the theory of Doctors GALVANI, VALLI and others, which ſuppoſes that the Nerve is electrified plus and the Muſcle minus, reſembling the Leyden Phial, by ſhewing that the Muſcles are convul⯑ſed 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 Muſcles which are convulſed, and when the Muſcle which is convulſed makes no part of the Circle in which the Matter that is put in motion paſſes.
- 4. I HAVE proved, that the Muſcles are convulſed whilſt the current of the Electrical Matter is paſſing from them and from the ſmaller Branches of the Nerves into their Trunks; and as a Muſcle is never thrown into Action by the Nervous Energy, except when this paſſes from the Trunk of the Nerve into its Branches, and from theſe into the Muſcle, it appears that when, in theſe Experiments, the Muſcles were convulſed, the Nervous and the Electrical [42]Fluids were moving in oppoſite Directions; from which we may infer, that, in their Nature, they differ eſſentially from each other.
- 5. THE Nervous Energy is ſtopped by a tight Ligature or by the tranſverſe Inciſion of a Nerve, although its di⯑vided Parts are thereafter placed in contact with each o⯑ther; whereas the Electrical Fluid or the Fluid excited by the Metals, paſſes 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 Convulſions of the ſame Muſcles may be ex⯑cited by applying Mechanical or Chemical Stimuli to its Nerves; whereas Electrical Matter diſcharges itſelf ſuddenly.
HENCE I conclude,
- 1. THAT the Fluid, which, on the application of Metal⯑line Bodies to Animals, occaſions Convulſions of their Muſ⯑cles, is electrical, or reſembles greatly the Electrical Fluid.
- 2. THAT this Fluid does not operate directly on the Muſcular Fibres, but merely by the Medium of their Nerves.
- 3. THAT this Fluid and the Nervous Fluid or Energy are not the ſame, but differ eſſentially in their Nature.
- 4. THAT this Fluid acts merely as a Stimulus to the Nervous Fluid or Energy.
- 5. THAT theſe Experiments have merely ſhown a new mode of exciting the Nervous Fluid or Energy, without throwing any farther or direct Light on the nature of this Fluid or Energy.
- Citation Suggestion for this Object
- TextGrid Repository (2016). TEI. 5613 Experiments on the nervous system with opium and metalline substances made chiefly with the view of determining the nature and effects of animal electricity By Alexander Monro. University of Oxford Text Archive. University of Oxford, License: Distributed by the University of Oxford under a Creative Commons Attribution-ShareAlike 3.0 Unported License [http://creativecommons.org/licenses/by-sa/3.0/]. https://hdl.handle.net/11378/0000-0005-E010-B