478 DIGESTION. 



tion of 5 p. m.) which easily destroy pepsin (LANGLEY). Pepsin, on the 

 other hand, withstands better than propepsin the action of carbon dioxide, 

 which quickly destroys the latter. The occurrence of a rennin zymogen 

 and possibly also of a steapsinogen, in the mucous coat has been men- 

 tioned above. 



The question in what cells the two zymogens, especially the pro- 

 pepsin, are produced, has been extensively discussed for several years. 

 Formerly, it was the general opinion that the cover cells were pepsin 

 cells, but since the investigations of HEIDENHAIN and his pupils, LANGLEY 

 and others, the formation of pepsin has been attributed to the chief 

 cells. 1 



The Pyloric Secretion. That part of the pyloric end of the dog's 

 stomach which contains no fundus glands was dissected by KLEMENSIE- 

 wicz, one end being sewed together in the shape of a blind sac and the 

 other sewed into the stomach. From the fistula thus created he was 

 able to obtain the pyloric secretion of a living animal, later the secretion 

 from a pyloric fistula has been obtained in other ways. This secretion 

 is alkaline, viscous, jelly-like, rich in mucin, of a specific gravity of 

 1.009-1.010, containing 16.5-20.5 p. m. solids. It habitually con- 

 tains pepsin, which has been proved by HEIDENHAIN by observations 

 on a permanent pyloric fistula, and the amount may sometimes be con- 

 siderable. CONTEJEAN investigated the pyloric secretion in other ways, 

 and finds that it contains both acid and pepsin. The alkaline reaction 

 of the secretions investigated by HEIDENHAIN and KLEMENSIEWICZ 

 is due, according to CONTEJEAN, to an abnormal secretion caused by the 

 operation, because the stomach readily yields an alkaline juice instead 

 of an acid one under abnornal conditions. The reports of HEIDENHAIN 

 and KLEMENSIEWICZ have nevertheless been substantiated by AKER- 

 MANN, KRESTEFF, SCHEMLAKINE and others. 2 



The secretion of gastric juice under different conditions may vary 

 considerably. The statements concerning the quantity of gastric juice 

 secreted in a certain time are therefore unreliable. ROSEMANN ob- 

 served, on sham feeding in dogs, a secretion of 917 cc. in the course of 

 3J hours a considerable quantity. KUDO 3 found more pepsin in the 

 secreted juice when the quantity of juice was less. 



The Chyme and the Digestion in the Stomach. By means of the 

 chemical stimulation caused by the food, a copious secretion of gastric 



1 See footnote 1, p. 477. 



"Heidenhain and Klemensiewicz, 1. c.; Contejean, 1. c., Chapter II, and Skand. 

 Arch f. Physiol, 6; Akermann, ibid., 5; Kresteff, Maly's Jahresber., 30; Schemia- 

 kine Arch, des scienc. biolog. de St. Pe"tersbourg, 10. 



1 Rosemann, Pfluger's Arch. 118; Kudo, Bioch. Zeitschr. 16. 



