LECT. IVX. XV. INDUCED CONTRACTIONS. 279 



with all possible care the brain of a frog, prepared in the 

 ordinary method, and spread upon this organ the nerve of 

 the galvanoscopic frog. In several experiments made in 

 this way, I applied, to the lumbar plexuses, sometimes the 

 direct current sometimes the inverse one ; in others, I 

 touched the plexuses with potash, and invariably obtained 

 contractions in the inferior members, and convulsions of the 

 back. Yet the galvanoscopic frog,- whose nerve rested upon 

 the brain, never manifested induced contractions. 



This same experiment has been tried, and with the like 

 results, by applying the nerve of the galvanoscopic frog 

 upon the spinal marrow, the brain, and different parts of 

 dogs and rabbits : it is useless to say, that during the ex- 

 periments, we irritated the animal in various parts, in order 

 to be quite certain that the nervous action was propagated 

 and reached the nervous centres. 



The induced contractions are, then, excited only by a 

 muscle in contraction. 



I wished to examine whether these induced contractions 

 became weakened, by provoking them by means of a mus- 

 cle in which the contraction was also induced. In a word, 

 I have sought for induced contraction of the first, second, 

 and third order, &c. To do so, I prepared several galva- 

 noscopic frogs, and one only in the ordinary way, I then 

 arranged them in the following manner : I spread the 

 nerve of a galvanoscopic frog upon the muscles of the 

 thighs of the entire frog ; then upon the muscles of the leg 

 of the galvanoscopic frog, I spread the nerve of another 

 galvanoscopic frog, and so on. The whole apparatus was 

 placed upon turpentine. By exciting contractions in the 

 whole frog, by means of the current passed through the 

 lumbar plexuses, I frequently saw three galvanoscopic frogs 

 contract at the same time, and nearly all of them with 

 equal vivacity. This effect was constantly produced in 



