186 PHYSIOLOGICAL CHEMISTRY. 



mentally proved by several investigators, has nevertheless not yet 

 been confirmed. On the contrary, the statement of SCHIFF that a 

 substance forming pepsin, a " pepsinogen" or "propepsin" occurs in 

 the ventricle has been proved. LANGLEY has shown positively the 

 existence of such a substance in the mucous coat. This substance, 

 propepsin, shows a comparatively strong resistance to dilute alkalies 

 (a soda solution of 5 p. m.) which easily destroys pepsin (LANGLEY). 

 Pepsin, on the other hand, withstands better than propepsin the 

 action of carbon dioxide, which quickly destroys the latter (LANG- 

 LEY). The occurrence of a rennet zymogen in the mucous coat has 

 been mentioned above, 



The question in which cells the two zymogens, especially the 

 propepsin, are produced has been extensively discussed for several 

 years. Formerly it was the general opinion that the delomorphic 

 cells were pepsin-cells, but at the present time the theory univer- 

 sally prevails, based chiefly on the experiments of HEIDENHAIN" 

 and his pupils, supported by LANGLEY and others, that the forma- 

 tion of pepsin goes on in the adelomorphic or principal cells. 



The Pyloric Secretion. That part of the pyloric end of the 

 dog's stomach which contains no fundus glands was dissected by 

 KLEMENSIEWICZ, one end being sewed together in the shape of a 

 blind sack and the other sewed into the stomach. From the fistula 

 thus created he was able to obtain the pyloric secretion of a living 

 animal. This secretion is alkaline, viscous, jelly-like, rich in mucin, 

 of a specific gravity of 1.009-1.010, and containing 16.5-20.5 

 p. m. solids. It has no effect on fat, but acts, though very slowly, 

 on starch, converting it into sugar, and habitually contains pepsin 

 in rather large amounts. HEIDENHAIN has observed the same in 

 permanent pyloric fistula. 



The secretion of the juices of the stomach is dependent to a 

 great extent upon the excitement acting on the mucous coat of the 

 stomach, and it follows from this that the quantity of secretion 

 under different conditions must vary considerably. The statements 

 of the quantity of gastric juice secreted in a certain time are there- 

 fore so unreliable that they need not be taken into account. 



The Chyme and the Digestion in the Stomach. By the move- 

 ments of the walls of the stomach the contents are kneaded and the 

 food-particles pressed against each other and divided. By means of 



