398 THE NERVOUS SYSTEM IN GENERAL, [ch. ii. 



perfectlj free/^ And elsewhere : " if the nerve of a muscle be 

 compressed, or tied, or divided, and then irritated, provided 

 it be fresh and moist, the irritation will produce in the muscle 

 to which the nerve is distributed the same movements as it 

 would have produced, if the continuity of the nerve with the 

 brain had remained unbroken. This proposition having been 

 proved with regard to the voluntary nerves, is here shown to 

 be applicable to the organic nerves.'^^ In the same work 

 (p. 237), he observes : " it is not necessary to the excitation of 

 muscular action by irritation of the nerves, that the nerve be in 

 connection with either the brain or spinal cord ; for irritation of 

 a nerve entirely separated from the spinal cord and brain, ex- 

 cites the same muscular contractions as irritation of a nerve in 

 unbroken connection wdth them.^' And in a sentence before 

 quoted,^ he remarks : " Thus, when after the destruction of 

 that part of the spinal cord from which it proceeds, a nerve is 

 irritated, it still, as before, throws the limb into contractions, 

 to which it is distributed. The same thing takes place in the 

 medulla spinalis after division of the medulla oblongata. In 

 short, if the head or whole brain be removed, and the heart 

 taken away, and the animal be apparently dead, on irritating in- 

 dividual nerves, or the spinal cord, the muscles are convulsed.^' 

 This vis nervosa, which remains in the nerves when separated 

 from the brain, is not exhausted by one or two muscular con- 

 tractions they excite when irritated, but is equal to the produc- 

 tion of numerously repeated movements, as I observed in a frog, 

 the spinal cord of which I divided in the back» It survived this 

 wound several days, and during the whole of that period, by 

 irritating that portion of the spinal cord which was below the 

 section, I excited innumerable convulsions in the lower extremi- 

 ties, nor did these die sooner than the whole frog. I am com- 

 pelled to defer a more detailed and accurate account of these and 

 similar experiments to another opportunity, as this is not the 

 proper place. That the vis nervosa can remain a long time in the 

 nerves, independently of the brain, seems to be proved by the 

 state of paralytic limbs, the nerves of which are deprived of all 

 connection with the brain on account of some preternatural com- 

 pression, and yet for a long period the paralysed muscles are 



• Memoires sur la Nature Sensible et Irritable, torn, i, p. 245, exper. 225. 

 = Elem. Phys., torn, iv, pp. 337, 338. 



