Digestion. 141 



very little ; as previously mentioned, we have no knowledge 

 of the nerves which govern the secretion of gastric juice > 

 there is no nerve the artificial stimulation of which has led 

 to a secretion of the fluid. 



The movements of the wall of the stomach are excited 

 by the presence of food or irritation applied to the mucous 

 membrane, and these movements may be increased by 

 stimulation of the vagus nerve. It is found, however, that 

 when the nerves leading to the stomach are divided so as 

 to completely cut the organ off from any nervous influence, 

 it still possesses the power of contraction, this being prob- 

 ably induced by the ganglia found in its walls. 



The stomach is supplied by the pneumogastrics, which 

 are here both non-medullated nerves, and also by the 

 splanchnics through the semilunar ganglion. Irritation of 

 the vagus leads to powerful contraction of the stomach 

 walls, whilst irritation of the splanchnics causes the move- 

 ment to cease ; the vagus is therefore an augmentor nerve 

 to the muscle of the stomach, whilst the splanchnics are 

 inhibitory. On the contrary, the vagus supplies the blood- 

 vessels of the stomach with inhibitory fibres, whilst the 

 splanchnics supply them with constrictor fibres. 



It is probable that the different muscular layers forming 

 the wall of the stomach have a separate source of nerve 

 supply, so that the circular can act independently of the 

 longitudinal fibres. 



Of the fibres opening and closing the cardia and pylorus 

 we have no knowledge. 



It has been previously mentioned that the nerve supply 

 to the third stomach of the ox is quite distinct from that 

 of the other stomachs ; irritation of the pneumogastric 

 produces contraction of all the stomachs but the omasum. 



Intestinal Digestion. 

 Small Intestines. — The chyme which is poured from the 

 stomach into the small intestines meets here with three 

 other digestive fluids, viz., the succus entericus, the bile, 

 and the pancreatic juice. 



