TROPHIC CENTRES AND XEKVES, SO CALLED. 441 



erful galvanization of the sympathetic produced great en- 

 largement of the pupil. 1 In such a case as this, it would not 

 be possible to make any observations on the influence of the 

 sympathetic upon the temperature. 



Trophic Centres and Nerves, so called. 



We have deferred the consideration of the so-called tro- 

 phic nerves until we had treated of the functions of the 

 sympathetic system, because the vaso-motor nerves, by their 

 influence upon the circulation, are evidently connected with 

 the phenomena of nutrition. It is not necessary to dwell 

 very minutely upon this point ; but cases of disease, as well 

 as experiments upon the inferior animals, show that when a 

 muscle is paralyzed, as a result of the abolition of nervous 

 influence and consequent disease, it becomes atrophied, its 

 fibres lose their characteristic structure, and finally become 

 incapable of contracting under any stimulus. As we have 

 seen that the cerebro-spinal nerves, in addition to their mo- 

 tor and sensory fibres, contain vaso-motor elements, it be- 

 comes a question whether the muscles be supplied with 

 special nerves, aside from those of motion and sensation 

 and the vaso-motor nerves, which preside over their nutri- 

 tion. Such could properly be called trophic nerves. Many 

 pathologists, relying upon the presence of certain lesions 

 of cells in the cord, in connection with cases of progressive 

 muscular atrophy, admit the existence of trophic cells and 

 nerves. It must be admitted, however, that these views 

 rest upon pathological facts alone, and have not been de- 

 monstrated by physiological experiments or observations. 



After what we have said, it is evident that proper nutri- 

 tion of the muscular system depends upon its exercise and 

 the integrity of its motor nerves. In the second place, the 

 history of monsters shows that the muscular system may be 



1 WAGNER, Note sur qicelques experiences sur la partie cervicale du nerfsympa- 

 ihique chez une femme decapitee. Journal de la physiologic, Paris, 1860, tome Ui., 

 p. 175. 



