sECT.vii.] NECESSITY OF NERVES TO NUTRITION. 425 



nutritive property to the nervous fluid, observing:^ " If the nerves 

 were not tubuli pervious to the nervous fluid, they could not be 

 nourished ; for the vessels surrounding the nerves on all sides 

 give nutrition to their cellular investment only, but the medullary 

 tubuli are nourished by the nervous fluid/' Tissot, moreover, 

 specifies three modes in which the nerves co-operate in nutrition. 

 In the first place, they pour animal spirits into the stomach, 

 intestine, lacteal vessels, &c., carry on digestion conjointly with 

 the gastric juice, impress an animal character on the food, and 

 act as a stimulus to the stomach itself. Secondly, they cause 

 the animal spirits to concur in nutrition by exciting muscular 

 action, and promoting digestion : thirdly, they promote the 

 secretion of gastric juice, saliva, &c.^ Tralles has lately again pro- 

 mulgated the doctrine denied by Haller and others, of a nutrient 

 property in the nervous fluid, observing that if a nerve be tied, 

 compressed, or destroyed, not only are motion and sensation 

 in the muscle destroyed, but also nutrition, and atrophy comes 

 on ; whence he thinks, the conclusion is undoubted, that some 

 fluid passes from the brain along the nerves to the muscles, by 

 which not only the muscles but the nerves also are nourished.^ 

 But all theories founded on the hypothesis of a nervous fluid 

 are untenable, if the hypothesis itself be demonstrated to 

 be untrue. 



For the better understanding what share the nerves have 

 in nutrition, it is advisable with Tissot to divide the nutritive 

 process into the two processes of assimilation, and the ap- 

 plication of the nutrient materials. No one can deny that 

 the nerves concur, at least remotely, in the assimilation and 

 transformation of food into nutrient material ; promoting, for 

 example, the secretion of saliva, of the gastric, intestinal, 

 and pancreatic juice, and of bile; by producing action of the 

 muscles subservient to mastication and deglutition ; by exciting 

 the movements of the stomach and intestines, nay, even those 

 of the heart, of respiration, and of the whole body, inasmuch 

 as all these actions concur in the elaboration of the nutrient 

 fluid. But the question arises, have the nerves also a share 

 in restoring the lost particles, and therefore in forming and 



' I])id. ill Iten Bande, Itcn Theile, § 153. 



^ Iteii Bandes, 2ter Theil, j 269. 



^ See Kemme's Zwcifel uud Eniiinerun}?en. 



