INTESTINAL NERVE-MECHANISM. 



123 





quate to excite prolonged action, except it be associated with 

 continuing congestion dependent upon other causes, such as the 

 vaso-raotor changes accompanying the general digestive process, 

 and the absorption of the prepared food-stuffs. 



With regard to the influence of other nerves, it seems to be 

 admitted on all sides that the vagus acts as an exciting nerve, 

 since stimulation of its peripheral part causes increased action, 

 and it is probable that its great efferent channel for impulses is 

 reflected through the brain. 



On the other hand, the splanchnic nerves, which come from 

 the thoracic sympathetic, are said to be inhibitors of the rnyen- 



FIG. 58. 



FIG. 59. 



FIG. 58. Meissner's plexus, low power. 

 FIG. 59. Meissner's plexus (high power), showing cells grouped at nodal 

 points. 



teric plexuses. This may be explained by their effect on the 

 small vessels which they no doubt control causing a change 

 in the blood supply. Be this as it may, the splanchnic seem to 

 have considerable influence on the intestinal movements. When 

 stimulated they commonly check the intestinal motions, but may 

 sometimes (as when the movements have ceased after death), give 

 rise to new movements. 



On account of this double action, it has been said that there 

 are two kinds of fibres, (1) inhibiting, which are easily excited, 

 and during life have greater influence, and (2), exciting, which, 

 though less excitable, retain their irritability longer. 



