250 



ARTIFICIAL DIGESTION OF THE PROTEIDS. 



alkaloids formed by the decomposition of albuminous bodies during the normal metabolic 

 processes taking place in the tissues. They are not formed by the activity of micro-organisms. 

 Some seem to be formed in muscle, and are closely allied to creatin and xanthin.] 



Peptones are undoubtedly those modifications of albumin or proteids which, after 

 their absorption from the intestinal canal into the blood, are destined to make good 

 the proteids used up in the human organism. By giving peptones (instead of 

 albumin) as food, life can not only be maintained, but there may even be an increase 

 of the body-weight (Plosz and Maly, Adamkiewicz). Very probably, before being 

 absorbed into the blood-stream, peptones are retransformed into serum-albumin 

 ( 192). 



Conditions affecting Gastric Digestion. The presence of already-formed peptones interferes 

 with the action of the gastric juice, in so far as the greater concentration of the fluid interferes 

 with and limits the mobility of the fluid-particles. Boiling, concentrated acids, alum, and 

 tannic acid, alkalinity of the gastric juice {e.g., by the admixture of much saliva), abolish the 

 action ; also sulphurous and arsenious acids and potassic iodide. The salts of the heavy metals, 

 which cause precipitates with pepsin, peptone, and mucin, interfere with gastric digestion, and 

 so do concentrated solutions of alkaline salts, common salt, magnesium and sodium sulphates. 

 A small quanity of NaCl increases the secretion (Griitzncr) and favours the action of pepsin. 

 Alkalies rapidly destroy pepsin, but less rapidly pro-pepsin (Langley). Alcohol precipitates the 

 pepsin, but by the subsequent addition of water it is redissolved, so that digestion goes on as 

 before. Any means that prevent the proteid bodies from swelling up, as by binding them 

 firmly, impede digestion. Slightly over half a pint of cold water does not seem to disturb 

 healthy digestion, but it does so in cases of disease of the stomach. Copious draughts of water, 

 and violent muscular exercise, disturb digestion ; while warm clothing, especially over the pit 

 of the stomach, aids it. Menstruation retards gastric digestion. [Oddi finds that the presence 

 of large quantities of ox bile, or even of its own bile in the stomach of a dog, does not affect the 

 activity of the gastric juice, does not precipitate peptones, and does not excite vomiting.] 



[Artificial Digestion. The action of gastric juice on proteids may be observed 

 outside the body, and we can prove, as is shown in the following table, after 

 Rutherford, that pepsin and an acid e.g., hydrochloric, along with water are 

 essential to the formation of gastric peptones : 



[In all animals, gastric digestion is essentially an acid digestion, and between the 

 native proteid, fibrin, albumin, or any other form of proteid, and the end-product 

 peptone, there are numerous intermediate substances, many of whose properties and 

 characters have still to be investigated. 



[Exclusion of the Stomach. Ogata finds that if the stomach be divided at the pyloric end so 

 as to exclude the stomach from the digestive apparatus, a dog can be nourished for a long time 

 by introducing food through the pylorus into the duodenum. A dog has lived several years 

 after excision of its stomach (Czcrny). Raw flesh so introduced is digested more rapidly in the 

 small intestine than in the stomach. The stomach not only digests, but it acts on the connective- 

 tissue of flesh so as to prepare the latter for intestinal digestion. ] 



II. Action on other Constituents of Food. Milk coagulates when it enters the 

 stomach, owing to the precipitation of the casein, and in doing so it entangles 

 some of the milk-globules. During the process of coagulation, heat is given 

 off. The free hydrochloric acid of the gastric juice is itself sufficient to pre- 

 cipitate it; the acid removes from the alkali-albuminate or casein the alkali which 

 keeps it in solution. Hammarsten separated a special ferment from the gastric 



