156 HAND-BOOK OF PHYSIOLOGY. 



nutrition, because in plants and the early embryo, and in the lowest 

 animals, in which no nervous system is developed, nutrition goes on with- 

 out it. But this is no proof that in animals which have a nervous system, 

 nutrition may be independent of it; rather, it may be assumed, that in 

 ascending development, as one system after another is added or in- 

 creased, so the highest (and, highest of all, the nervous system) will 

 always be inserted and blended in a more and more intimate relation with 

 all the rest; according to the general law, that the interdependence of 

 parts augments with their development. 



The reasonableness of this assumption is proved by many facts show- 

 ing the influence of the nervous system on nutrition, and by the most 

 striking of these facts being observed in the higher animals, and especially 

 in man. The influence of the mind in the production, aggravation, and 

 cure of organic diseases is matter of daily observation, and a sufficient 

 proof of influence exercised on nutrition through the nervous system. 



Independently of mental influence, injuries either to portions of the 

 nervous centres, or to individual nerves, are frequently followed by de- 

 fective nutrition of the parts supplied by the injured nerves, or deriving 

 their nervous influence from the damaged portions of the nervous centres. 

 Thus, lesions of the spinal cord are sometimes followed by mortification 

 of portions of the paralyzed parts; and this may take place very quickly, 

 as in a case in which the ankle sloughed within twenty-four hours after 

 an injury of the spine. After such lesions also, the repair of injuries in 

 the paralyzed parts may take place less completely than in others; so, in 

 a case in which paraplegia was produced by fracture of the lumbar verte- 

 brae, and, in the same accident, the humerus and tibia were fractured. 

 The former in due time united: the latter did not. The same fact was 

 illustrated by some experiments, 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 destroy the cord, it was found that the end of the 

 tail was reproduced more slowly than in other salamanders in whom the 

 spinal cord was left uninjured above the point at which the tail was ampu- 

 tated. 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 corresponding 

 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 degeneration of tissue in paralyzed 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 



