INFLUENCE OF NERVOUS SYSTEM. 387 



trated by some experiments of Dr. Baly, in which having, 

 in salamanders, cut off the end of the tail, and then thrust 

 a thin wire some distance up the spinal canal, so as to de- 

 stroy the cord, he found that the end of the tail was repro- 

 duced more slowly than in other salamanders in whom the 

 spinal cord was left uninjured above the point at which 

 the tail was amputated. Illustrations of the same kind 

 are furnished by the several cases in which division or 

 destruction of the trunk of the trigeminal nerve has been 

 followed by incomplete and morbid nutrition of the corre- 

 sponding side of the face ; ulceration of the cornea being 

 often directly or indirectly one of the consequences of such 

 imperfect nutrition. Part of the wasting and slow dege- 

 neration of tissue in paralysed limbs is probably referable 

 also to the withdrawal of nervous influence from them 

 though, perhaps, more is due to the want of use of the 

 tissues. 



Undue irritation of the trunks of nerves, as well as their 

 division or destruction, is sometimes followed by defective 

 or morbid nutrition. To this may be referred the cases 

 in which ulceration of the parts supplied by the irritated 

 nerves occurs frequently, and continues so long as the 

 irritation lasts. Further evidence of the influence of the 

 nervous system upon nutrition is furnished by those cases 

 in which, from mental anguish, or in severe neuralgic head- 

 aches, the hair becomes grey very quickly, or even in a few 

 hours. 



So many and various facts leave little doubt that the 

 nervous system exercises an influence over nutrition as 

 over other organic processes ; and they cannot be explained 

 by supposing that the changes in the nutritive processes 

 are only due to the variations in the size of the blood- 

 vessels supplying the affected parts. 



The question remains, through what class of nerves ia 

 the influence exerted ? When defective nutrition occurs in 

 parts rendered inactive by injury of the motor nerve alone, 



c c 2 



