196 GASTRIC DIGESTION 



of the teeth and thoroughly insalivated, are taken into the stomach : 

 muscular tissue with the muscular substance enveloped in its sarco- 

 lemma, bloodvessels, nerves, ordinary fibrous tissue holding the mus- 

 cular fibres together, interstitial fat, and a small quantity of albumins 

 and corpuscles from the blood, all combined with a considerable 

 quantity of inorganic salts ; albumin, sometimes unchanged, but usually 

 more or less thoroughly coagulated; fatty matters, sometimes in the 

 form of oil and sometimes enclosed in vesicles, constituting adipose 

 tissue ; gelatin and animal matters in a liquid form extracted from meats, 

 as in soups ; casein, in its liquid form, united with butter and salts in 

 milk, and coagulated, in connection with various other matters, in cheese ; 

 vegetable nitrogenous matters, of which gluten may be taken as the type ; 

 vegetable fats and oils; sugars, from both the animal and vegetable 

 kingdoms, but chiefly from vegetables ; different kinds of amylaceous 

 substances ; and finally, organic acids and salts, derived chiefly from 

 vegetables. These matters, particularly those from the vegetable king- 

 dom, are united with more or less innutritions matter, such as cellulose. 

 They also are seasoned with aromatic substances, condiments etc., 

 which are not directly used in nutrition. 



The various articles described as drinks are taken without any 

 considerable admixture with the saliva. They embrace water and cer- 

 tain nutritious or stimulant infusions (including alcoholic beverages) 

 with a small proportion of inorganic salts in solution. 



Action of the Gastric Juice on Meats. The digestion of meat in the 

 stomach is far from complete. The parts of the muscular structure 

 most easily attacked are the fibrous tissue holding the muscular fibres 

 together, and the sarcolemma, or sheath of the fibres themselves. If 

 the gastric juice of the dog is placed in a vessel with finely chopped 

 lean meat and kept in contact with it for a number of hours at about 

 100 Fahr. (37.78 C), agitating the vessel occasionally so as to subject, 

 so far as possible, every particle of the meat to its action, the filtered 

 liquid will be found increased in density, its acidity diminished, and 

 presenting all the evidences of having dissolved a considerable portion 

 of the tissue. There always, however, will remain a certain portion 

 that has not Leen dissolved. Its constitution is nevertheless materially 

 changer! , for it no longer possesses the ordinary character of muscular 

 tissue and easily breaks down between the fingers into a pultaceous 

 mass. On subjecting this residue to microscopical examination, it is 

 found not to contain any ordinary fibrous tissue ; and the fibres of 

 muscular tissue, although presenting the well-marked and characteristic 

 striae, are broken into short pieces and have very little tenacity. It is 

 evidently only the muscular substance that remains, the connective 



