THE REGULATION OF GASTRIC SECRETION. 213 



We may conclude, therefore, that the increased secretion of 

 gastric juice, brought about through the injection of extracts 

 of the mucosa of the pyloric end of the stomach, is due to the 

 injection of some substance which is produced in this region 

 of the stomach under the influence of certain of the products 

 of gastric digestion. This substance is called gastric secre- 

 tin. The mucous membrane of the fundus of the stomach 

 does not contain this substance. As to the nature of gastric 

 secretin but little can be said. It does not seem to belong to 

 the class of ferments, for it is not destroyed by boiling. In 

 this regard it is similar to pancreatic secretin. 



If now, in the light of the experimental facts which have been 

 cited above, we try to explain the progress of normal gastric 

 digestion the following may be said: The initial secretory 

 period, which is noted after an ordinary meal eaten in the 

 ordinary way and with desire, is explained by the psychic 

 effect of eating. This psychic effect lasts for three or 'four 

 hours. The digestion periods following this are independent 

 of the central nervous system and are governed by chemical 

 agents. In the case of meat we find a reason for the continued 

 secretion of gastric juice after the initial psychic period in the 

 chemical constitution of the food itself. It contains sub- 

 stances which, acting on the mucosa of the pylorus, cause 

 the elaboration of gastric secretin. The same holds true for 

 predigested foods that is, foods containing digestion products 

 which act in a similar way upon the pyloric mucosa. In the 

 case of the remaining substances, such as bread,white of egg, 

 etc., we can say that under normal circumstances the psychic 

 juice starts their digestion, and in this process chemical 

 substances are formed which bring about an elaboration of 

 secretin, and this keeps up the gastric flow after the psychic 

 element has come to rest. This idea is supported by the fact 

 that the products of digestion formed in the stomach of one 

 dog act as excitants of gastric secretion when introduced 

 into the stomach of another. The clinical application which 

 may be made of these experimental facts is too evident to 



