THE FUNCTIONS OF THE DIGESTIVE ORGANS. 523 



out which is rich in enterokinase. Boiled pancreatic juice, however, has 

 no such effect. The secretion of the intestinal juice is, according to this, 

 by no means such a simple process as has ordinarily been assumed. Its 

 composition is determined by at least two factors which are largely 

 independent of one another. The production of enterokinase, and the 

 formation of the other constituents of the secretion produced by the 

 intestinal membrane and its glands, are distinct processes. The intestinal 

 juices have a favorable action upon the digestion of albumin, not only 

 by reason of the enterokinase, but, according to many observations, also 

 on account of the other ferments in the pancreatic juice. These juices 

 have on the whole a quite similar effect to the bile. 



In describing the secretion of the stomach, we saw that the amount and 

 composition of the gastric juice are dependent upon various external 

 influences, and that above all psychic influences play an important part. 

 Is the secretion of the pancreatic juice similarly affected? The following 

 observations give us some light with regard to this important question. 

 In the case of herbivora in which the digestion is, so to speak, a continuous 

 process, the secretion of the pancreatic juice takes place continually. In 

 carnivora, it is possible to trace at once some connection between the 

 introduction of food and the subsequent digestion. 



Pawlow called attention, in the first place, to the following experiment: 

 If a few drops of 0.5 per cent hydrochloric acid are introduced into the 

 stomach of a dog having a pancreatic fistula from which only a few drops of 

 pancreatic juice are flowing in a minute, there is then an increase in the 

 secretion after a short time. If instead of acid a little lime-water is intro- 

 duced into the dog's stomach, the contrary effect is obtained. Phosphoric, 

 lactic, citric, and acetic acids each have the same effect as hydrochloric 

 acid. The concentration of the acid, moreover, greatly influences the 

 secretion, as the following experiment shows i 1 250 cubic centimeters of HC1 

 of the following concentrations were introduced into the stomach of a dog: 



The pancreatic gland reacts promptly with the acid, and even with 

 concentrations which barely have an acid taste. Other irritants, such as 

 pepper and mustard, are without influence. Acid, therefore, is to be 

 regarded as exerting a specific effect upon the pancreas. Naturally the 



Pawlow: Vorlesungen etc., op. cit. p. 150. 



