The quantity of the gastric juice secreted in twenty- four hour, was determined by Bidder and Sehmidt (Die l crduilungssafic. etc. t in the sheep to be one-eighth. and in the dog one-tcnth of the weight of the body. If the latter ratio were true for men, a man of 140 pounds' weight would secrete about. It pounds of this fluid daily. In the ease of Catharine Katt, the mean daily quantity amounted 10 110 less than 31 pounds, or to inure titan a fourth part of the weight of her body. On this calculation, a man of 140 pounds weight would daily secrete 37 pounds of gastric juice.
The uses of this fluid in reference to digestion are clear. It serve, not only to dissolve. but also to modify the nitrogenous elements of the food I such as albumen, fibrin, casein, and, in short. all animal food except fat, and the blood-forming portion of vegetable food), converting them into new substances. termed peptunes, xVil jell, al though they coincide in their chemical composi• Lion, and in many of their physical properties, with the substances from they are derived, differ essentially from them in their more ready solubility in water, and in various chemical rela tion,. Titus. albumen is converted by the gastric juice into allminen-peptone. fibrin into fibrin peptone. etc. According to the investigations of Aleissner. the albumin:Iles are simultaneously de composed or broken up into peptones and sub stances which lie terms pnrapeptones. which lat ter are not further changed by the action of the gastric juice, but are converted into peptones by the action of the pancreatie juice, With which they come in contact in the duodenum.
All the best observers agree that the gastric juice exerts no apparent act ion on the non-nit rog (mous articles of food—namely, the fats and the carbohydrates :sugar. starch, ell. ;11-. LH/W eyer, the fats exert a favorable influence on the digestion of nitrogenous matters. it is probable that they undergo some slight. although not ap preciable, modification. rIelatin and the gelat inous are, as far as is known, the only nitrogenous articles of food whieh are not eon vented into peptones anti parepeptones by the action of the gastric juiee.
Although the main object of the gastric juice is to dissolve the albuminates. etc. (e.g. the con tents of the egg, flesh. cheese. etc..). it appear from the experiments of Lehmann. Sehmidt. and others, that it cannot dissolve the quantity neces sary for the due nutrition of the organism. Ac cording to Lehmann. gastric juice can only
solve one-twentieth of its weight of coagulated albumen while Schmidt makes the quantity as low as one-forty-fifth. Now. since n dog seeretes about one-tenth of its weight of gastric juice daily. it would only be able—even taking Leh mann', estimate, which is more than twice as high as digest live parts of dry or coagulated albumen for •vi ry 1000 parts of its weight but a dog, in order to keep in condition on all exclusive flesh diet—and this is its natural food—should take 50 parts of flesh, containing 111 parts of dry alhuminates. for every 1000 parts f its weight. Ilenee its gastric juice only suf fices for the digestion of half the albuminates necessary for nutrition—a result which is in accordance with the observed fact that a eon Fiderable portion of the albuminates enters the duodenum in an state, and which will be explained when we consider the part which the intestinal juiee—the fluid secreted by the various glands in the mucous membrane of the small intestine—takes in the digestive process. On comparing the experiments made on dogs with those made on Catharine Ktitt, it ap pears that in the human subject the gastrie di gestion of the albuminates is much more imper fect than even in the dog.
The process of gastric digestion is slow. Ac cording to Beaumont's researches on Alexis Saint Martin, the mean time requited for the digestion of ordinary animal food, such as butcher's meat, fowl, and game, was from two hours and three quarters to four hours.
Freriehs and Don ders maintain that the absorption of the pep tones commences in the stomach: but the view generally adopted is, that the albuminates, etc., which are con verted into peptones, are for the most part taken up by the lac teals. The rapidity with which aqueous solutions of iodide of potassium. the alka line carbonates, lae tate::, citrates, etc., pass into the blood. and thence into the urine, saliva, etc., shows that the al , sorption of fluids must take place very short , ly after they are swal . lowed, and there is - little doubt that the (capilla ries) of the stomach constitute the principal ehannel through which they pass out of the intestinal tract into the Hood. As the veins of the stomach, which formed by the union of these capillaries. con tribute to form the portal vein ( see the absorbed matters pas- directly to the liver. and probably stimulate it to increased se cretion (Fig. 4).