THE FUNCTIONS OF THE DIGESTIVE ORGANS. 525 



more hydrochloric acid there is produced, the greater becomes the alka- 

 linity of the blood. This excess of alkalinity is given" up by the blood to 

 the cells of the pancreas which employ it in the production of the pan- 

 creatic juice. With the pancreatic juice, this alkali, chiefly as sodium 

 carbonate, flows into the intestines, and meets there the hydrochloric acid 

 from the stomach. Here again common salt is formed which may enter 

 into the circulation anew. At the same time, by 'means of such a mech- 

 anism the alkalinity of the blood varies only within narrow limits. We 

 should not, however, imagine that the process takes place in such a simple 

 form that the cells of the pancreas are immediately brought into activity 

 by the increased alkalinity of the blood, which, in turn, is caused by the 

 production of hydrochloric acid in the stomach. Plausible though such an 

 assumption may be, it does not correspond with the results of experimental 

 research. The production of acid does not have such a direct influence 

 upon the activity of the cells in the pancreas. We must remember that 

 hydrochloric acid introduced from without, also effects the production 

 of the pancreatic juice. In the last case the alkalinity of the blood is 

 diminished rather than increased. Although the above-described salt- 

 cycle appears to be a very suitable arrangement, it does not, on the other 

 hand, stand in direct connection with the action of the acid upon the 

 function of the pancreatic gland. We must, on the contrary, conceive this 

 to be due to some phenomenon brought about by the action of the acid 

 upon the membrane. 



We shall soon come to a very important observation of Bayliss and Star- 

 ling which will shed considerable light upon the nature of the action of 

 the hydrochloric acid. 



It is interesting to find that even the composition of the pancreatic juice 

 is adjusted to that of the acid in the chyme, for, as Walther 1 has showed, 

 the amount of organic material in the former is regulated by the amount of 

 acid in the latter. The juice produced by hydrochloric acid alone contains 

 less organic material and more alkali than the normal. Here again we 

 meet with the same conditions as in the secretion of the gastric and intes- 

 tinal juices. Likewise the formation of the pancreatic juice is not that of a 

 simple substance. It must not be thought that the cells of the pancreas 

 always yield one and the same secretion. At one time the juice is rich in 

 ferments, and at another time alkali predominates. For the present we do 

 not know whether this is due to the fact that cells are influenced differ- 

 ently by various kinds of nervous stimulation, or whether particular cells 

 are provided with quite definite functions. The fact that even the juice 

 rich in alkali, which is produced by the action of acid alone, always con- 

 tains ferments, makes it seem probable that the action of the individual 

 cells is governed by the nature of the stimulation it receives, and that it is 



1 Inaug. Diss. St. Petersburg (1896). 



