ON INDUCED CONTRACTIONS. 3l7 



elastic bodies. The phenomenon of induced contraction would seem to be a first fact 

 of induction of that force which circulates in the nerves and which arouses muscular 

 contraction. 



Admitting that we cannot give a satisfactory explanation of the phenomenon of 

 induced contraction by recurring to electricity or any other known causes, as I think 

 I have abundantly proved, it appears to me that we cannot, confining ourselves to 

 a first fact, as is that of induced contraction, interpret it differently from what we 

 have done. The induced contraction is only a new phenomenon of nervous force, a 

 phenomenon of which we have given the principal laws in this memoir. It seems 

 to me therefore more just to call that henceforth muscular induction, which I have 

 hitherto called induced contraction. 1 shall conclude this memoir with some appli- 

 cations of muscular induction to physiology. 



By the experiment described above (fig. 14.), it is proved that the muscular induc- 

 tion is propagated in a nerve at the same time towards the two extremities — towards 

 the muscle as well as towards the nervous centre. If the muscular induction not 

 only acts upon the nerve in contact with the muscle but also through some inter- 

 posed bodies, it is natural to admit that when a muscular mass enters into contrac- 

 tion by the irritation acting on one of its nerves, the phenomenon of induction should 

 occur in all the other nerves. And even wishing to yield for a moment to the analogies 

 that exist between the electric current and the nervous force, we might be led to be- 

 lieve that this induction should take place upon the excited nerve which is the cause 

 of the contraction. Could we not perhaps from this deduce a physical explanation 

 of a well-established physiological fact, that within certain limits the activity of the 

 muscles increases in proportion as the contraction is aroused in them ? 



It also appears to me that a great number of those movements which occur in us 

 and in animals independently of the will, but yet following others occasioned by the 

 will, may be considered as phenomena of muscular induction. I leave to physiolo- 

 gists the continuation of these studies, which appear to me worthy of all their in- 

 terest. 



I shall terminate by citing an experiment which I think proves an action of this 

 nature. Having prepared a frog in the ordinary manner, I cut one of the nerves 

 that constitute one of the lumbar plexuses, and I divide it precisely at the point of 

 exit from the vertebral column. Having extended the frog upon turpentine, I draw 

 on one side the severed nerve, and 1 irritate it either with the current or with an 

 alkali. Thus very strong contractions are produced in the thigh, and at the same 

 time, if the frog is very lively, there are contortions in the back and movements in its 

 superior limbs. 



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