496 DIGESTION 



stomach has been studied by feeding animals with potatoes containing 

 varying percentages of hydrochloric acid. With an acidity of 0.25 per 

 cent, the rate of discharge was increased, but it became slower when the 

 acidity rose to 1 per cent. With an acidity of 0.5 per cent, the rate of 

 discharge was about the normal. Hyperacidity, therefore, causes a retar- 

 dation of the emptying of the stomach. 



The consistency of the food appears to have little influence on its rate of 

 discharge from the stomach at least in the case of potatoes. Dilution 

 of protein food, however, increases the rate. Distinctly hard particles 

 in the food retard the stomach evacuation. 



There is usually a considerable amount of gas in the part of the stomach 

 above the entrance of the cardia, on account of which this part of the 

 stomach has sometimes been called the stomach bladder. In the upright 

 position this gas forms a bright area in the x-ray plate (Fig. 155), but 

 when the person reclines it spreads to a new location. Its presence may 

 influence gastric digestion by preventing the contact of the food with 

 the mucous membrane, and by interfering with the efficiency of the peri- 

 staltic waves in moving the food. Considerable gas therefore retards the 

 emptying of the stomach, as has been shown experimentally by x-ray 

 observations on animals fed with the standard amount of food followed 

 by the introduction of air. It was noted that the air did not diminish 

 the frequency or strength of the peristaltic waves, but that these could 

 not efficiently act on the food. When along with gas there is also atony 

 of the stomach walls, the retardation in the discharge will, of course, be 

 still more pronounced. The temperature of the swallowed food does 

 not appear to have much influence on the stomach movements or on the 

 the rate of discharge from the organ. 



