224 



GASTRIC DIGESTION. 



the muscular substance always presenting its characteristic stria?, on micro- 

 scopical examination. Bernard, in experiments with the gastric juice of 

 different animals, found the fluid from the stomach of the rabbit or the horse 



much inferior, as re- 

 gards the activity of its 

 action upon meat, to 

 the gastric juice of the 

 dog. 



Whether the gas- 

 tric juice be entirely 

 incapable of acting 

 upon the muscular 

 substance or not, the 

 above-mentioned facts 

 clearly show that mus- 

 cular tissue usually is 

 not completely digest- 

 ed in the stomach. 

 The action in this or- 

 gan is to dissolve the 

 intermuscular fibrous 

 tissue and the sarco- 

 lemma, or sheath of 

 the muscular fibres, 

 setting the true muscular substance free and breaking it up into small par- 

 ticles. The mass of tissue is thus reduced to the condition of a thin, pulta- 

 ceous fluid, which passes into the small intestine, where the process of diges- 

 tion is completed. 



The constituents of the blood, albuminoids, corpuscles etc., which may 

 be introduced in small quantity in connection with muscular tissue, probably 

 are completely dissolved in the stomach. 



Action upon Albumen, Fibrin, Caseine and Gelatine. 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 albumen 

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

 stance, called 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 ; and the digestion of 

 albumen in this form is more rapid than when it has been completely coagu- 

 lated by heat. It is a matter of common as well as of scientific observation, 

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

 boiled or uncooked. 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 absorption of albumen takes place in the 

 stomach ; and if any albumen pass out of the pylorus, the quantity is very small. 



d b c 



FIG. 65. Matters taken from the pyloric portion of the stomach of a 



dog during digestion of mixed food (Bernard). 



a, disintegrated muscular fibres, the striae having disappeared ; 6, c, 

 muscular fibres in which the striae have partly disappeared ; d, d, d, 

 globules of fat ; e, e, e, starch ; g, molecular granules. 



