ACTION OF THE GASTRIC JUICE IN DIGESTION. 245 



The constituents of the blood (albumen, corpuscles, etc.), which may be introduced 

 in small quantity in connection with muscular tissue, are probably completely dissolved 

 in the stomach. 



Action upon Albumen, Fibrin, Caseine, and Gelatine. Dr. Beaumont thought that 

 raw albumen, or white of egg, became first coagulated in the stomach and was afterward 

 dissolved ; but this has been disproved by numerous other observers, who, however, have 

 experimented chiefly on dogs. Reference to the experiments of Beaumont will show that 

 the phenomena which he described as taking place in a mixture of equal parts of white 

 of egg and gastric juice, kept at the temperature of the body for three hours, do not really 

 indicate coagulation. He states that " in ten or fifteen minutes, small, white flocculi began 

 to appear, floating about ; and the mixture became of an opaque and whitish appearance. 

 This continued slowly and uniformly to increase for three hours, at which time the fluid 

 had become of a milky appearance ; the small flocculi, or loose coagula, had mostly dis- 

 appeared, and a light-colored sediment subsided to the bottom." If white of egg be mixed 

 with equal parts of pure water and be gently stirred with a glass rod, the same small, 

 white flocculi will make their appearance, and the mixture will become opaque and 

 whitish. This is due to the disengagement of shreds of the membranes in which the 

 clear albumen is contained ; these being invisible in pure white of egg, from the fact that 

 the two substances have the same refractive power. A very different appearance is 

 presented when water containing even a small quantity of nitric acid is added to a liquid 

 containing albumen. True coagulation then takes place, and the mixture becomes imme- 

 diately filled with large, dense clots ; or the mass may become nearly solidified, if the acid 

 be added in sufficient quantity. Longet and Schiff injected a filtered watery mixture of 

 albumen into the stomach of a dog through a fistulous opening and found that no coagu- 

 lation took place. 



The action of the gastric juice upon uncooked white of egg is to disintegrate its 

 structure, separating and finally dissolving the membranous sacs in which the pure 

 albumen is contained. It also acts upon the albumen itself, forming a new fluid substance, 

 called albuminose, or albumen-peptone, which, unlike albumen, is not coagulated by heat 

 or acids, but is precipitated by alcohol, tannin, and many of the metallic salts. 



The digestion of raw or imperfectly-coagulated albumen takes place with considerable 

 rapidity in the stomach. Beaumont gave St. Martin the white of two eggs when the 

 stomach was empty and found that it had been completely disposed of in an hour and a 

 half. The digestion of albumen in this form is more rapid than when it has been com- 

 pletely coagulated by heat. 



Coagulated white of egg is almost if not entirely dissolved by the gastric juice. If a 

 cube of albumen in this condition be subjected to the action of the gastric juice at the 

 temperature of the body, taking care to agitate it occasionally, the edges and corners 

 gradually become rounded, and nearly the whole mass finally breaks down and is dissolved, 

 having previously become softened so that it may be easily crushed between the fingers. 

 Usually, one or two points appear in the mass, which are acted upon with difficulty or 

 may resist solution entirely. It is a matter of common as well as scientific observation, 

 that eggs when hard-boiled are less easily digested than when they are soft-boiled or raw. 



The products of the digestion of raw or of coagulated albumen (albumen-peptone) 

 are essentially the same. It is probable that the entire process of digestion and absorp- 

 tion of albumen takes .place in the stomach, and, if any pass out of the pylorus, the 

 quantity is exceedingly small. 



Fibrin, as distinguished from the so-called fibrin of the muscular tissue, pr musculine, 

 is not a very important article of diet. The action of the gastric juice upon it is more 

 rapid and complete than upon albumen. The well-known action upon fibrin of water 

 slightly acidulated with hydrochloric acid has led some physiologists to assume that the 

 acid is the only constituent in the gastric juice necessary to the digestion of this principle ; 



