to the Agency of the Nerves. 119 



4. Another circumstance which seems to me very adverse 

 to the supposition, that division of the eighth pair of nerves, 

 and division of any nerve supplying a voluntary muscle, act on 

 the secretions of the stomach and the motions of the muscle 

 equally by cutting off a supply of galvanism, is this, that no se- 

 cretion at all takes place after the former operation, whereas 

 powerful muscular contractions may be excited by applying 

 stimuli to the nerve below the point of division long after the 

 latter. According to the galvanic theory, these contractions 

 are excited by galvanism, remaining in the nerve after its divi- 

 sion*. Why, then, does not galvanism enough remain in the 

 nerves of the stomach after the division of the eighth pair, to 

 carry on digestion for a certain length of time ? 



These considerations seem to render it extremely doubtful 

 whether the changes which take place in the nervous system and 

 aifect the muscular or secreting organs, or the nervous actions, 

 can be of the nature of galvanism ; and if they be not galvanic, 

 Dr, Wilson Philip's experiment above referred to, becomes an 

 Experimentum Crucis against their being essential to secretion. 



But, even if the actions of nerves be galvanic, there are 

 very strong reasons for thinking that they cannot be essential 

 to secretion and nutrition. 



1. The secretion of the stomach was found to be suppressed, 

 in Dr. W. Philip's experiments, by other lesions of the nervous 

 system besides cutting the eighth pair of nerves. It was sup- 

 pressed in rabbits nearly or entirely by destroying the lower 

 half, or even less than the lower half, of the spinal marrow. 

 (See Expts. 58, 59, 60, p. 171.) In these cases the stomach 

 must still have had the supply of galvanism which it receives 

 through the eighth pair of nerves, and in fact all that it receives 

 from the brain and upper half of the spinal marrow, a much 

 greater supply than that, the interception of which in the former 

 experiments was supposed to stop the secretion. Where we find 

 80 great an effect produced on the secretion of the stomach by 

 a cause which, even on the supposition of its deriving galvanism 



• See Haller, lihrn. mr les I'atikx Senaibles it Initables, Exp. 201,202, 214, 

 220,-225, and p. 237. 



