MOTION OF THE STOMACH. 



113 



about this wave of movement. To explain this discrepancy it 

 may be urged that the local nerve and muscle mechanism in the 

 tissues of the oesophagus are capable by themselves of carrying 

 out peristaltic contraction independently of the central nerve 

 organs, but that this power is, under ordinary circumstances, 

 held in check by the vagus. The inhibition is temporarily sus- 

 pended as a sequence of pharyngeal spasm, and consequently a 

 wave of peristaltic contraction is excited in the oasophageal mus- 

 cles, either in response to the direct stimulus of a passing bolus, 

 or as a result of impulses reflected along the vagus channels from 

 the medulla. 



FIG. 54. 









iagram of Wall of the Stomach, showing the relative thickness of the 

 mucous membrane (a, 6, c), and the transverse (e), oblique (/), and longi- 

 tudinal muscle fibres. 



Motion of the Stomach. The stomach and greater part 

 of the intestinal tract move freely within the abdomen, being 

 covered by the smooth serous lining of that cavity, which also 

 keeps in position, so as to restrict their movements, those parts, 

 such as the duodenum, into which the ducts of large glands open. 

 When the stomach is empty it hangs with the great curvature 

 downwards, and the muscular coats are quiescent. On being 

 filled it is passively rotated on its long axis, so that the greater 

 curvature is turned forwards, here meeting with less resistance, 

 and the lesser curvature is turned backwarks to its line of attach- 



10 



