434 Nervous Disturbances. 



complexity of the nervous mechanism and even more because of the 

 great variety of processes and causes possible in case of such dii^- 

 turbances. 



Trophic, vasomotor and secretory disturbances depending upon 

 nervous influences. — Of the vast number of cells which make up the 

 animal body, there are, it is true, some cells, which are independent 

 of the nervous system, acquiring their nutrition and performing 

 their function by means of their own parenchyma alone. These are 

 the isolated blood cells and lymph cells. All the other cells and tis- 

 sues, however, in the matter of their metabolism, growth and main- 

 tenance of existence, depend upon the nervous system ; and die if 

 they be separated from it. The part played by the nerves in tliis 

 connection is known as the trophic influence. This is most clearly 

 apparent in nerve fibres themselves, which invariably degenerate if 

 divided from their ganglia or if the latter be the seat of disease. In 

 warm-blooded animals disintegration in the form of fatty degenera- 

 tion sets in as early as from four to six days. A nerve fibre may 

 be looked upon as the elongated process of a ganglion cell, and in 

 this conception disintegration is easily understood when it is re- 

 called that, as taught by *Verworn and Krehl, any part of a cell 

 which has been separated from its nucleus is sure to die. There is. 

 it is true, a certain degree of individuality of the different segments 

 of the nerve fibres so far as concerns their nutrition, metabolism and 

 diseases, but permanent maintenance of their integrity is only as- 

 sured by their continuity with the ganglion cells. And reversely the 

 central portions of a neuron (that is to say, the ganglion cell) suffer 

 if their connection with the peripheral nerves is broken ; for example, 

 after section of a nerve atrophy of the central portion also occurs, 

 perhaps extending to the ganglion. It is recognized that the integ- 

 rity of the ganglia and nerves is dependent upon the exercise of 

 their function, that functional stimulation is essential for mainte- 

 nance of their nutrition and life. Atrophy usually appears in the 

 voluntary muscles as soon as they lose the influence of their proper 

 ganglion cells in the anterior horns of the cord or of the equally 

 important cerebral parts ; that is, when these become diseased or the 

 communicating paths are interrupted or injured. The muscles, there- 

 after incapable of voluntary movements, are thus rendered immobile 

 (inactive, or paralyzed), become decreased in volume from diminu- 

 tion in size of their individual fibres (simple atrophy, atrophy from 

 disease), or may perhaps undergo granular and fragmentary disin- 

 tegration of their contractile material (degeneration atrophy) ; a 

 rapid shrinkage resulting, arid transformation of the muscle into flat, 



