COMPOSITION OF GASTRIC JUICE 



403 



FIG. 278. Operation on the Stomach to Form 

 an Isolated Pouch with Nerves Intact. S, 

 Isolated sac; V, cavity of stomach; A, A, open- 

 ing at the abdominal wall. 



animal for 5 to 10 minutes, an abundant flow of gastric juice will begin. 

 Pawlow calls this the psychic secretion. 



If an esophageal fistula has also been performed the dog may be allowed 

 to eat the meat, of course swal- 

 lowing it out of the esophageal 

 fistula back into the plate. In 

 this experiment an abundant 

 flow of gastric secretion takes 

 place and may continue for an 

 hour or more. 



If a gastric pouch has been 

 performed by Pavlov's method, 

 the animal may be allowed to 

 eat the food, swallowing it into 

 the stomach. In this case the 

 reflex secretion just described 

 takes place as usual, but is fol- 

 lowed after an hour or an hour 

 and a half by a second increase 

 in the quantity of secretion. 

 This second increase has been 

 ascribed to the reflexes origi- 

 nating in the stomach, possibly from the reflex stimulating action of the 

 digestive products themselves. 



10. Composition of Gastric Juice. Test a sample of gastric juice 

 obtained from a gastric fistula, as follows: 



Reaction. Gastric juice is strongly acid. Test for free hydrochloric acid 

 as follows: Gastric juice turns congo-red to a blue color. Gastric juice plus 

 0.5 per cent, alcoholic solution of dimethyl-amido-azobenzol develops a 

 cherry-red color, a reaction that is given by free hydrochloric acid. Com- 

 bined hydrochloric acids and organic acids do not give the color. Giinz- 

 burg's reagent, consisting of 2 per cent, phloroglucin and i per cent, vanillin 

 in 80 per cent, alcohol, produces a rose-colored mirror on porcelain in the 

 presence of free hydrochloric acid. The test is very delicate. 



The lactic acid sometimes present in the contents of the stomach is 

 derived partly from the sarcolactic acid of muscle and partly from lactic-acid 

 fermentation of carbohydrates. Lactic acid (C 3 H S O 3 ), if present, gives the 

 following test: A solution of 10 cubic centimeters of a 4 per cent, aqueous 

 solution of carbolic acid, 20 cubic centimeters of water, and one drop of ferric 

 chloride is made; forming a blue-colored mixture. A mere trace of free lactic 

 acid added to such a solution causes it to become yellow. Inasmuch as 

 mineral acids also discharge the color, the lactic acid should first be removed 

 from the gastric contents by shaking with ether and the test tried out with a 

 solution of the residue after evaporation of the ether. 



