210 PHYSIOLOGY OF ALIMENTATION. 



through mechanical stimulation a gastric juice which even 

 approximated the acidity obtained by sham feeding. That 

 they obtained any acid secretion at all is due to errors in 

 experiment, such as not washing out the stomach properly, 

 not waiting until the stimulation to gastric secretion from the 

 previous meal had entirely worn off, or causing a psychic 

 secretion of the gastric juice by exciting the dog through the 

 smell of food on the hands, the appearance of the attendant 

 who usually fed the dog, etc. 



Having settled now that the mechanical properties of the 

 food are in themselves unable to call forth a secretion of gas- 

 tric juice we turn to its chemical properties. What chemical 

 constituents of the food bring about a secretion of juice from 

 the stomach? In order to investigate this problem a dog 

 with a miniature stomach, and possessing in addition a fistula 

 passing into the main cavity, can best be used. The food 

 undergoing study is introduced into the main cavity, and the 

 amount and quality of the juice which flows from the isolated 

 cul-de-sac examined. In order not to bring about a psychic 

 secretion of the gastric juice, it is best to introduce the food 

 while the dog is asleep, or while the dog's attention is dis- 

 tracted from what is going on if the animal is awake. 

 Water, first of all, has an exciting effect upon the gastric 

 glands. It has been found by CHIGIN that when 400 to 500 

 c.c. of water are introduced into the large stomach of a dog, 

 a small but constant secretion of juice occurs from the lesser 

 one. This fact had been previously found by HEIDENHAIN. 

 Smaller quantities of water are not so effective, and if only 

 100 to 150 c.c. are injected into the large stomach, usually 

 no secretion of juice at all occurs. The results are the same 

 when before the introduction of the water the vagi nerves 

 are divided below the diaphragm or in the neck. 



Neither solutions of sodium chloride, sodium bicarbonate, or 

 hydrochloric acid excite a flow of gastric juice. According to 

 CHIGIN 0.05 to 1 percent sodium bicarbonate solutions, when 

 introduced in the same amounts as proved effective when 



