28 STUDIES IN DIGESTION 



the gastric fistula, as in a case of gastrostomy for 

 cancer of the oesophagus. 



It was found that dogs would survive this procedure 

 for months without suffering. The effects of feeding 

 on the flow of gastric juice could easily be determined. 

 When the animal was shown a savoury meal, not 

 only did his eyes sparkle and mouth water, but the 

 stomach " watered " also. An even greater effect 

 was produced by allowing him to swallow it, though 

 of course it never reached the stomach. If, however, 

 he learned by disappointing experience that he would 

 not be allowed to partake of the meal so temptingly 

 displayed, he ceased to show signs of appetite, and 

 there was no flow of gastric juice. 



Section of both vagi had the remarkable effect of 

 preventing the flow of this " appetite juice," by 

 blocking the down path of the reflex. On the other 

 hand, stimulation of the vagi (with certain precau- 

 tions) induced constantly a flow of gastric juice 

 after an interval of several minutes. 



We have considered so far the nervous regulation 

 of the flow of gastric juice, and now turn to the 

 second or chemical regulation. 



If water was introduced directly into the stomach, 

 a slight flow of gastric juice was excited. Alcohol 

 had no more effect than water. Mechanical irritation 

 by solid bodies produced no flow. Food substances 

 dissolved in water, such as proteins, starch, salts, and 

 drugs, had no more effect than the water itself. To 

 this rule there were a few significant exceptions. 

 Extractives (that is, the soluble substances in meat, 

 contained in broths, meat extracts, etc.) excited a 



