uo 



DIGESTION. 



substance in question was precipitated from the watery infusion by 

 the addition of alcohol, and dried ; and if dissolved afterward in 

 acidulated water, it was found to exert a solvent action on boiled 

 white of egg. This substance, however, did not represent precisely 

 the natural ingredient of the gastric secretion, and was probably a 

 mixture of various matters, some of them the products of com- 

 mencing decomposition of the mucous membrane itself. The name 

 pepsine, if it be used at all, should be applied to the organic matter 

 which naturally occurs in solution in the gastric juice. It is alto- 

 gether unessential, in this respect, from what source it may be 

 originally derived. It has been regarded by Bernard and others, 

 on somewhat insufficient grounds, as a product of the alteration of 

 the mucus of the stomach. But whatever be its source, since it is 

 always present in the secretion of the stomach, and takes an active 

 part in the performance of its function, it can be regarded in no 

 other light than as a real anatomical ingredient of the gastric juice, 

 and as essential to its constitution. 



Pepsine is precipitated from its solution in the gastric juice by 

 absolute alcohol, and by various metallic salts, but is not affected 



by ferrocyanide of potassium. 



Fi S- 30. It is precipitated also, and 



coagulated, by a boiling tem- 

 perature; and the gastric 

 juice, accordingly, after being 

 boiled, becomes turbid, and 

 loses altogether its power of 

 dissolving alimentary sub- 

 stances. Gastric juice is also 

 affected in a remarkable 

 manner by being mingled 

 with bile. We have found 

 that four to six drops of dog's 

 bile precipitate completely 

 with 3j of gastric juice from 

 the same animal ; so that the 

 whole of the biliary coloring 

 matter is thrown down as a 



deposit, and the filtered fluid is found to have lost entirely its 

 digestive power, though it retains an acid reaction. 



A very singular property of the gastric juice is its inaptitude for 

 putrefaction. It may be kept for an indefinite length of time in a 



CONFERVOID VEGETABLE, growing in the Gas- 

 tric Juice of the Dog. The fibres have an average 

 diameter of 1-7000 of an inch. 



