720s 



PHYSIOLOGY OF THE NERVOUS SYSTEM. 



tractions of the galvanoscopic leg will not take 

 place. If, however, a slight tear be made in 

 the gold leaf, then the nerve may be excited. 

 It is possible that this may arise from the 

 electricity being carried off by the gold leaf, so 

 that it does not affect the nerve at all. Matteucci 

 never succeeded in obtaining the induced con- 

 tractions when a solid body was interposed 

 between the nerve and muscle, however thin 

 it might have been and whatever might be its 

 nature; for this purpose he used flakes of mica 

 extremely thin, flakes of sulphate of lime, gold 

 leaf, paper smeared with glue, and leaves of 

 vegetables.* 



On the other hand, in interposing some sub- 

 stances which are known to be bad conductors 

 of electricity, the contractions were obtained. 

 The induced contractions may be excited if the 

 nerve be laid upon the skin over the muscles of 

 the inducing frog. " The experiment," says 

 Matteucci, " never fails of success, whether the 

 inducing contraction be excited by the electric 

 current or by any stimulus applied to the lum- 

 bar plexuses of the inducing frog." The use 

 of a very bad conducting body, Venice turpen- 

 tine, did not prevent the induced contractions. 

 The nearly solid Venice turpentine was ren- 

 dered more or less liquid by adding to it a little 

 of the volatile oil of turpentine, and with this the 

 muscles were smeared over, and the nerve of 

 the galvanoscopic frog was wetted. To prove 

 the bad conducting powers of the mixture em- 

 ployed, one pole of the exciting pile was ap- 

 plied to the muscle and the other to the galva- 

 noscopic frog without exciting the least con- 

 traction. Yet the contractions were induced 

 in the galvanoscopic frog by stimulating the t 

 muscles of the thigh. This experiment clearly 

 proved, as Matteucci remarks, that the induced 

 contraction may be excited through a stratum 

 of an insulating substance that prevents the 

 propagation not only of the muscular and proper 

 currents, but also of that current which excites 

 the inducing contraction. 



We are forced then by the results of the re- 

 markable experiments above detailed to adopt 

 the conclusion at which Matteucci has himself 

 arrived that there is no current of electricity 

 in the act of muscular contraction. What then 

 is the evolved force ? It is either an electric 

 discharge^ or a force very analogous to electri- 

 city, affecting nerves in a similar way, travelling 

 apparently with great rapidity, traversing bodies 

 which the galvanic current cannot traverse, and 

 yet restrained by substances which freely con- 

 duct it. 



I confess myself at a loss to understand how 

 Matteucci comes to regard this as a phenomenon 

 of the nervous force. In truth, it is a pheno- 

 menon which accompanies muscular contrac- 



* Phil. Trans. 1845, On induced contractions. 



t From a letter addressed to M. Dumas by Pro- 

 fessor Matteucci, and published in the Comptes 

 Rendus for March 15, 1847, it appears that he now 

 is rather disposed to regard it as an electric dis- 

 charge, as he says, " C'est apres avoir prouve que 

 des decharges electriques de la bouteille tcllemciit 

 faibles qu'elles ne pouvcnt etre montrees par aucun 

 instrument, excepte par la grenouillc, quo j'ai 

 pense quo la contraction induitc pouvail etre due a 

 une dechargc electrique de ce genre." 



tion, and has no relation to the nervous force, 

 excepting so far as that is the excitant of the 

 muscular action. The essential point of the 

 phenomenon is, that during the contraction of 

 a muscle a nerve which is laid on it is stimulated 

 just as it would be by electricity, and causes 

 the muscles to which it is distributed to contract. 

 The electric discharge from a muscle which is 

 excited to contract through the exercise of ner- 

 vous power is in close analogy with the electric 

 discharge from the electrical organ of the 

 Gymnotus or Torpedo, which is excited through 

 the same agency. 



Now the proved existence of a muscular 

 force, the developement of which is accompa- 

 nied with heat, and most probably electricity, 

 and in some instances, if the statements of 

 Quatrefages be correct, with light, justifies us in 

 adopting the opinion, as regards the nervous 

 force, that this is of an analogous kind, yet exhi- 

 biting still less resemblance to electricity than 

 the muscular force; and it strikingly illustrates 

 the remark of Faraday, that if there be reasons 

 for supposing that magnetism is a higher rela- 

 tion of force than electricity, so it may well be 

 imagined that the nervous power may be of a 

 still more exalted character and yet within the 

 reach of experiment. 



We are thus led to these conclusions respect- 

 ing the muscular and nervous forces. 



1. That both are polar forces and in close 

 analogy with light, heat, electricity magnetism. 



2. That either may be excited by or trans- 

 formed into the other the nervous may excite 

 the muscular, or the muscular the nervous. It 

 seems not improbable that it is by this reaction 

 of the muscular upon the nervous force that the 

 muscular sense is developed, and as Matteucci 

 has ingeniously suggested, many movements 

 independent on the will, yet following others 

 which may be voluntary or otherwise, may result 

 from the same cause. 



3. That the same analogy which exists be- 

 tween electricity and magnetism is found be- 

 tween these organic polar forces ; the muscular 

 being more nearly allied to the former, the ner- 

 vous to the latter. 



4. Both these forces are dependent on the 

 healthy nutrition of their respective tissues, 

 muscle and nerve, and the slightest disturbance 

 in that process in either tissue will readily 

 affect the intensity of the force. 



5. Nevertheless there is a certain mutual de- 

 pendence between these two tissues and their 

 forces ; for the exercise of each is, within certain 

 limits, impossible without the other; and as 

 this exercise is necessary to maintain healthy 

 nutrition, so these forces are to a certain extent 

 dependent on each other for their normal deve- 

 lopement. The practitioner in medicine will 

 duly appreciate the great importance of this 

 conclusion. 



The mutual reactions of the nervous and 

 muscular forces constitute a new and highly 

 important field of inquiry, which, if duly culti- 

 vated, may clear up many obscurities in the 

 physiology and pathology of the nervous system. 



Having thus far considered certain generali- 

 ties in the physiology of the nervous system, 

 \se niny now proceed to inquire into the share 



