384 INNERVATION. [CHAP.XI. 



teucci's experiments have shewn that the former has some marked connexion 

 with muscles, arid with those of the leg more especially ; and he has found 

 that the same circumstances which increase or diminish the muscular current, 

 exert a similar influence upon the proper current. But they differ remarkably 

 in point of duration ; as the latter continues long after all traces of a muscular 

 current have ceased to be discoverable. It is highly probable, as before 

 stated, that the true source of this current will be found in some anatomical 

 peculiarity of the frog. 



As in the ordinary phenomena of the nutrition of muscles, by which their 

 state of passive contraction or tone is maintained, electricity is developed, it 

 is most reasonable to expect, that during active contraction there should 

 be a development of electricity, as there is of heat likewise, according to 

 Becquerel and Breschet's observations. This is shewn by Matteucci in a very 

 beautiful experiment, which we have frequently repeated with the same re- 

 sults. Place a prepared frog upon an insulating plane ; then prepare the 

 of another frog with the crural nerve dissected out and left attached to tl 

 leg, the thigh being removed. Place the nerve of this leg upon one or botl 

 thighs of the other frog, and every time that those legs are excited to contn 

 by a galvanic or a mechanical stimulus, contractions will be produced in tl 

 second leg, which is connected with the first only by the contact of its nen 

 with the surface of their muscles. The same effect will be produced if tl 

 nerve of the frog's leg be placed on the muscles of a warm-blooded animal, - 

 a rabbit, for instance, care being taken to remove any thick aponeurosis 

 which may cover the latter. 



If an insulating substance be placed between the muscles of the thigh ai 

 the nerve of the leg, no action will take place. The same effect is observe 

 when gold-leaf is interposed ; but if the gold-leaf be torn, to however sligl 

 a degree, the leg will be thrown into contraction. 



The electricity developed during the contraction of the muscles, stimulat 

 the nerve which is laid upon them ; the interposition of a non-conducting 

 substance prevents the electric discharge from reaching the nerve ; and 

 leaf, being a better conductor than nerve, carries the electricity along i1 

 passing by the nerve. 



4. The study of the effects of electricity applied in various ways upoi 

 nerves, has led to some highly interesting and curious results. 



Nobili ascertained that, in passing an electric current through the luml 

 nerves of a frog, contractions occurred under different circumstances, accord- 

 ing to the state of vitality of the nerves. He divided the vitality of the 

 nerve into five periods, during each of which different phenomena were pi 

 duced by the passage of the current. In the first period, the direct curreni 

 or that directed from the brain to the nerves, caused contractions in the 

 muscles on closing the circuit ; the inverse current, or that from the nerve 

 to the brain, on opening it. In the second period, the direct current cam 

 contractions on closing the circuit, and slight ones on opening it ; the invei 

 current causes coptractions only on opening the circuit. In the third peric 

 contractions occur only on closing the direct current and opening the inverse. 

 In the fourth period, contractions occur only on closing the direct current ; 

 and in the fifth, the nerve ceases to be influenced by the electrical stimulus. 

 Marianini, who subsequently studied this subject, affirms that contractions 

 take place only under two circumstances, namely, from the closure of the 



