DIGESTION I93 



the former is accomplished, according to Pavlov, by a special activating 

 ferment secreted by the epithelium of the small intestine and termed entero- 

 kinase. 1 



The rapidity with which pancreatic juice in the presence of bile and 

 hydrochloric acid (under conditions such as are present in the duodenum) 

 can develop sufficient fatty acid to form an emulsion was determined by 

 Rachford to be two minutes. The activity of steapsin is thus shown to be 

 very great. 



Intestinal Juice. This fluid is a product of the activities of the cells 

 lining the follicles or glands of Lieberkiihn. Owing to its admixture with 

 other secretions and to the profound disturbance of the digestive function 

 caused by the establishment of intestinal fistulas, this fluid has rarely been 

 obtained in a state of purity or in quantities sufficient for accurate analyses 

 or for experimental purposes. Its physiologic properties and functions are 

 therefore imperfectly known. Various attempts have been made by physi- 

 ologists, by the employment of different methods, to obtain this secretion. 

 The method usually employed is that of Thiry and Vella. This consists in 

 dividing the intestine at two places, about eight or ten inches apart, restoring 

 the continuity of the intestine, and then uniting the two ends of the resected 

 portion to the edges of two openings in the abdominal walls. The resected 

 portion, being supplied with blood-vessels and nerves, maintains its nutrition 

 and secretes a more or less normal juice. 



When obtained from a dog under these circumstances the intestinal 

 juice is watery in consistence, slightly opalescent, light yellow in color, 

 alkaline in reaction, with a specific gravity of i.oio. Chemic analysis 

 reveals the presence of proteins, mucin, and sodium carbonate. 



The intestinal juice obtained by Tubbey and Manning from a small 

 portion of the human intestine (ileum) was opalescent, occasionally brownish 

 in color, alkaline, and had a specific gravity of 1.006. On the addition of 

 hydrochloric acid, carbonic acid was given off, showing the presence of 

 carbonates. It contained proteins and mucins. 



Physiologic Action of the Intestinal Juice. The part played 

 by the intestinal juice in the digestive process is yet a subject of discussion, 

 as the results obtained by different observers are in some respects con- 

 tradictory, due to the fact that animals, as well as human beings, have been 

 the subjects of experimentation. By reason of its contained enzymes the 

 intestinal juice acts: 



i. On Proteases and Peptones. Even though the proteins have been reduced 

 by the action of the gastric and pancreatic juices to the stage of proteoses 

 and peptones they are not yet in a condition to be absorbed. The 

 further stage in their digestion appears to be their reduction, as stated" 

 in a foregoing paragraph, to amino-acids or their immediate anteced- 

 ents. This change has been attributed to the action of the intestinal 

 juice or a contained enzyme to which the name erepsin was given by its 

 discoverer Cohnheim. 



1 An activator may be defined as an agent, which secreted by some one organ, is capably of 

 converting an inactive agent, secreted by some correlated organ, near or remote, into an active 

 agent by some chemical interaction. Thus the antecedents of many enzymes, either before or 

 after their discharge by gland cells are inactive and require to be modified in some unknown way 

 before they become functionally active. The term activator is usually applied to inorganic 

 agents, the term kinase to organic agents. 

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