APPLIED PHYSIOLOGY 



elastic tissue in the wall of the stomach, which forms 

 two layers one in the muscularis mucosse, and the 

 other and more definite layer between the submucous and 

 muscular coats. In chief measure, however, the tension 

 within the empty stomach is not the result of such 

 factors as these, but is due simply to pressure exerted 

 upon the stomach from without by the abdominal wall 

 and by other viscera, especially the liver. Thus, the 

 intragastric pressure is lowest when the individual is 

 lying upon the right side, when the weight of the liver 

 is taken off the stomach ; and it is worth noting that this 

 is the position which it is best to adopt if vomiting be 

 urgent, as in sea-sickness. It is of interest, too, to 

 observe that, contrary to expectation, the intragastric 

 tension is not increased in pregnancy, a fact which has 

 important bearings upon some of the theories which 

 have been advanced to explain the occurrence of vomit- 

 ing in that condition. 



After food enters the stomach the intragastric tension 

 in the fundus rises to a pressure of 10 to 12 centimetres 

 of water, and if enough food be taken to raise the 

 pressure to 20 centimetres, the feeling of distension 

 becomes painful. This, however, is nothing compared 

 with the pressure which may be exerted upon the 

 stomach by pressure from without, for it has been found 

 that forced expiratory efforts with the diaphragm fixed 

 and depressed may raise the pressure within the stomach 

 to that of 330 centimetres of water, and such is the 

 ' squeeze ' brought to bear upon the organ in the act of 

 vomiting. 



The rise in intragastric tension after the taking of 



