LECT. XIV. XV. INDUCED CONTRACTIONS. 277 



that the induced contractions are also manifested when 

 the nerve, placed upon the muscles in contraction, is un- 

 touched. 



By using the frog, thus prepared, I have studied induced 

 contractions, employing such an arrangement that the nerve 

 which is in contact with the muscle in contraction is al- 

 ready excited, either by a current or some other stimulant. 

 For this purpose I either included the galvanoscopic frog 

 in the circuit of a voltaic pair, or applied a drop of a very 

 weak alkaline solution upon the nerve. Every time that 

 the inducting muscles contracted, there was invariably in- 

 duced contraction, whether the nerve by which this last 

 was excited was previously irritated or not ; and, conse- 

 quently, when even the muscle on which this contraction 

 took place was already contracted. Notwithstanding this 

 contraction of the galvanoscopic frog, there is no diffi- 

 culty in perceiving the induced contraction which ensues. 



Numerous experiments, equally simple, prove, that what- 

 ever may be the manner in which the nerve of the induct- 

 ing muscle be excited, if the contraction be absent, the 

 induction is equally so. I shall confine myself to the rela- 

 tion of some of the principal ones. If the nerves have 

 been divided at two or three places in the inducting mus- 

 cles, in order to prevent the contraction taking place, in- 

 duction is constantly absent. 



If, without cutting the nerves, we make incisions into 

 all the tendinous extremities of the muscles of the thigh, 

 and if, moreover, we make some transverse incisions in the 

 same muscles, avoiding the nervous cords, both the in- 

 ducing and induced contractions are wanting. 



By carefully dividing all the muscles of the leg of a frog, 

 we may expose the nervous filament which traverses it. 

 If we irritate this nerve with either the current or any 

 other stimulant, after having spread the nerve of the gal- 



