ACTION ON ALBUMIN, FIBRIN, CASEIN AND GELATIN 197 



tissue and the sarcolemma having been dissolved. Even on adding 

 fresh juice to the undigested matter, this is not dissolved to any con- 

 siderable extent, the residue not being sensibly diminished in quantity, 

 and the muscular substance still presenting the characteristic striation. 



Whether the gastric juice be incapable of acting on the muscular 

 substance or not, the above-mentioned facts clearly show that muscular 

 tissue usually is not completely digested in the stomach. The action 

 of the gastric juice is to dissolve the intermuscular fibrous tissue and 

 the sarcolemma, or sheath of the muscular fibres, setting the true mus- 

 cular substance free and breaking it up into small particles. The mass 

 of tissue is thus reduced to a thin pultaceous condition, and it passes 

 into the small intestine, where its digestion is completed. The constitu- 

 ents of the blood, albumins, corpuscles etc., which may be introduced 

 in small quantity in connection with muscular tissue, probably are 

 completely dissolved in the stomach. 



Action on Albumin, Fibrin, Casein and Gelatin. The action of the 

 gastric juice on uncooked white of egg is to disintegrate its structure, 

 separating and finally dissolving the membranous sacs in which the 

 albumins are contained. It also acts on the albumins, forming albu- 

 min-peptones, which, unlike albumin, are not coagulated by heat 

 or acids, but are precipitated by alcohol, tannin and many of the 

 metallic salts. The digestion of raw or imperfectly-coagulated albu- 

 mins takes place with considerable rapidity in the stomach ; and the 

 digestion of albumins in this form is more rapid than when they have 

 been coagulated by heat. It is a matter of common as well as of 

 scientific observation, that eggs when hard-boiled are less easily di- 

 gested than when they are soft-boiled or uncooked. The products of 

 the digestion of raw or of coagulated albumins (albumin-peptones) are 

 essentially the same. It is probable that the entire process of diges- 

 tion and absorption of albumins takes place in the stomach ; and if any 

 albumins pass out of the pylorus, the quantity is small. 



Fibrin, as distinguished from myosin, is not a very important article 

 of food. The action of the gastric juice upon it is more rapid and com- 

 plete than on albumins. The well-known action on 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 substance ; but observations on the 

 comparative action of acidulated water and of artificial or natural gastric 

 juice show that the presence of the organic matter is necessary to the 

 digestion of this as well as of other nitrogenous alimentary substances. 

 The action of water containing a small proportion of acid is to render 

 fibrin soft and transparent, frequently giving to the entire mass a jelly- 



