SEC. 5. THE INFLUENCE OF THE NEK VOUS SYSTEM 

 ON NUTRITION. 



In the preceding sections we had more than once to refer to 

 the possibility of the nervous system having the power of directly 

 affecting the metabolic actions of the body, apart from any 

 irritable, contractile, or secretory manifestations. Thus the phe- 

 nomena of diabetes cannot, at present at all events, be satisfactorily 

 explained as a purely vaso-motor effect, and the production of heat 

 is, as we have seen, under the special guidance of the nervous 

 system. In the case of the salivary glands we meet with the 

 striking fact that when all the nerves of a gland have been divided 

 the gland enters into a peculiar condition during which it pours 

 forth a continuous, so-called 'paralytic' secretion, while ultimately 

 the tissue of the gland degenerates. This result differs perhaps 

 from the wasting of a muscle which follows upon severance of its 

 motor nerve, since this may be, partly at all events, explained by 

 the fact that the muscle is no longer functional ; and indeed, if the 

 muscle is rendered functional, if it is directly stimulated for 

 instance from time to time with a galvanic current, the atrophy 

 may be for a while at least postponed, though as we have seen 

 (p. 92) the postponement is probably not indefinite. But the 

 salivary gland at all events in the case in question is functional, it 

 does go on secreting; nevertheless in the absence of its usual 



