248 APPLIED PHYSIOLOGY 



the other hand, the presence of insoluble lumps of food 

 in the stomach seems to excite a powerful contraction of 

 the pylorus, which expresses itself as * stomach - ache.' 

 The result is that such undissolved lumps are retained 

 in the stomach for more prolonged digestion and attrition. 

 The presence of an ulcer or fissure in the near neighbour- 

 hood of the pylorus would seem to be capable of inhibit- 

 ing the relaxation of the latter, which normally occurs 

 when peristaltic waves reach it. In this way the outlet 

 may be blocked and dilatation of the stomach result. 



The rate at which different substances leave the 

 stomach seems to depend upon many different circum- 

 stances, chief of which is the mechanical form and con- 

 sistence of the substance in question. Fluids begin to 

 pass out of the stomach almost at once, warm fluids 

 sooner than cold. * Slops ' begin to pass out almost as 

 soon, and even solids may begin to be discharged in less 

 than half an hour. These observations show the im- 

 portance of attending to the mechanical form of the food 

 in cases in which the stomach has difficulty in emptying 

 itself. 



The chemical composition of the food, however, is not 

 without influence upon the rate of its discharge. Some 

 observations by Cannon* are of interest in this con- 

 nection. As the result of experiments in the Harvard 

 Physiological Laboratory, he states that ' it was proved 

 that when carbohydrates, proteins, and fats of the same 

 consistency are fed separately and in equal amounts, they 

 do not leave the stomach at the same rate. Fats remain 

 long in the stomach. Their discharge into the small 

 * Amer. Journ. of Med. Sciences, 1906, cxxxi. 563. 



