THE DIGESTIVE SYSTEM. 311 



more tubular in shape, until finally, four or five hours after the com- 

 mencement of digestion, the process is complete. 



The precise mechanism by which the movements of the stomach 

 are originated and carried out has not been definitely ascertained. 

 Branches of the vagus nerves and of the sympathetic system are supplied 

 to the viscus, and form connections with the plexus which lies between 

 the layers of the muscular coat. Fine filaments from the latter are 

 distributed to the muscle fibres. Division of the two vagi is followed 



FIG. 122. Tracing showing relaxation of the muscular wall of the stomach ot a cat on 

 stimulation of splanchnic nerves. (Elliott. ) 



by defective movements, so that the stomach is incompletely emptied 

 after each meal. Stimulation of the vagi leads to temporary diminution 

 of muscular tone, followed by increased contraction (fig. 121), whereas 

 the sympathetic system has on the whole an inhibitory effect on the 

 muscular wall (fig. 122). 



The influence of the central nervous system is, however, not 

 essential for the stomach movements, for normal contractions may be 

 observed in the isolated organ placed in warm saline solution. It is still 

 an open question whether these contractions are myogenic in origin, or 

 are due to a local reflex through the plexus in the muscular coat. In any 

 case, the movements may be considered to be under a certain degree of 



