194 PHYSIOLOGY CHAP. 



The consistency of the food is not, of course, the sole factor that 

 determines the rate of gastric evacuation. If this were so, all 

 mobile fluids would leave the stomach with the same rapidity, 

 which is not the case. On introducing half a litre of water, 

 60 per cent is eliminated in 15 minutes, while if the same 

 quantity of beer is introduced, only 11 per cent is excreted. 

 Milk, soup, sops, again, stay longer in the stomach than would 

 be expected, judging merely from their consistency. Moritz 

 interprets this fact as meaning that all these substances (unlike 

 water, which is an indifferent substance) function as stronger 

 chemical, and partly also as mechanical stimuli, as shown also by 

 a greater secretion of acid. On the strength of this fact, Moritz 

 holds soups to be a food, particularly adapted to prepare the 

 stomach for the introduction of more solid viands. 



The application of radioscopy (by admixture of bismuth sub- 

 nitrate with the food) to the study of the movements of the stomach 

 in digestion, has led to a distinct advance in methods and compara- 

 tive results. The most interesting researches in this direction are 

 those of Cannon (1898), and Koux and Balthazard (1907), both 

 with the usual animals experimented on and with man. 



According to these authors the stomach may functionally be 

 divided into two portions, the fundus (or cardia) and the pylorus. 

 The latter is mechanically the most active part of this organ, and 

 exhibits, radioscopically, ample peristaltic movements throughout 

 the whole period of digestion. 



The cardiac region only shows rare waves of contraction which 

 propel the food-stuffs towards the fundus. In the fundic part the 

 chyme travels very slowly in the direction of the pyloric antrurn. 

 The movements of the pyloric antrum are set up in the part 

 nearest the fundus (pre-antral constrictions), and are mainly 

 effected by the circular fibres; the antrum contracts vigorously 

 and assumes the form of a tube. The (peristaltic) contraction 

 waves are separated, both in animals and in man, by an interval 

 of 10-20 sees. The pyloric orifice rarely opens in the first period of 

 digestion, while towards the close it relaxes in response to each 

 contraction of the antrum. 



The chyme is almost stationary in the fundus : it passes slowly 

 into the pyloric antrum where the food is thoroughly mixed with 

 the digestive juices and dissolves, owing to the vigorous move- 

 ments in this region. The alimentary mass, while continually 

 passing from fundus to antrum, perpetually flows back (especially 

 in the first periods of digestion) from antrum to fundus owing to 

 the increased pressure, which gives rise to the peristaltic waves in 

 the antrum when the pylorus remains closed. The chyme passes 

 more quickly and in larger quantities into the intestine, in 

 proportion as it is softer and more liquid in consistency. The 

 pyloric orifice opposes the passage of solid foods. On mixing 



