THE GASTRIC JUICE. 125 



viscid secretion, which contained pepsin and large amounts of mucin, 

 but no hydrochloric acid. A reversal of the experiment, on the 

 other hand, in which the fundus was thus isolated, showed that 

 here both pepsin and hydrochloric acid are secreted. As this 

 portion of the stomach contains both delomorphous and adelo- 

 morphous cells, the conclusion naturally suggests itself that the 

 hydrochloric acid is furnished only by the delomorphous cells^ 

 while the pepsin and the same apparently holds good for chy- 

 mosin is secreted by the adelomorphous cells. The latter are 

 hence also spoken of as pepsin calls, while the delomorphous cells 

 are similarly termed the oxyntic cells of the stomach. 



As in the case of the ptyalin of the saliva, however, it appears 

 that the ferments in question do not exist in the cells as such, but in 

 the form of proenzymes or zymogens, which are termed propepsin 

 or pepsinogen and prorennin or chymosinogen, respectively. 



It has thus been shown that an aqueous extract of the gastric 

 mucosa when treated with 1 per cent, of soda, and kept at a tem- 

 perature of 40 C., even for several hours, does not lose its digestive 

 power, and can be rendered physiologically active by subsequently 

 acidifying with hydrochloric acid to from 0.2 to 0.3 per cent., pro- 

 viding that the animal has previously fasted. If then, however, 

 such artificial gastric juice is neutralized, and then alkalinized with 

 soda to the extent of only 0.5 per cent., the solution is rendered 

 entirely inactive after a few seconds, when warmed to the tempera- 

 ture of the body, and it is to be noted that the subsequent addition 

 of hydrochloric acid is now no longer capable of restoring the 

 activity of the enzyme. This demonstrates, of course, that while 

 the proenzyme is more or less resistant to soda, the ferment is thereby 

 rapidly destroyed. On the other hand, it appears that pepsin is 

 more resistant to the influence of carbonic acid than propepsin. 

 Between chyrnosin and its zymogen similar relations exist. 



Of the chemical nature of the proenzymes and the manner in 

 which they are produced by the cells, practically nothing is known. 

 Nerve-influences, no doubt, are here at work, as in the case of the 

 salivary glands. At the same time the blood-supply is of moment, 

 and we find that during the process of digestion the blood-vessels are 

 dilated, and that the venous circulation is more rapid and the blood 

 of a light-red color. But as in the salivary glands, it is certain that 

 the height of the blood-pressure has only indirectly to do with the 

 activity of the glands. The proenzymes here, as there, are formed 

 through a specific activity on the part of the cells, from food- 

 material which is supplied by the lymph. 



Whether or not the transformation of the proenzymes into the 

 corresponding ferments occurs in the bodies of the cells has not been 

 definitely decided. It appears, however, that in the majority of 

 animals which have been examined in this direction the glands 

 secrete only the proenzymes, and that these are then rendered 

 physiologically active by the hydrochloric acid of the gastric juice. 



