326 THE INTESTINAL JUICE. 



As, therefore, the largest part of the biliary acids is returned to the blood, 

 it is clear that animals from which all the bile is lost through a biliary fistula, 

 without their licking it up, lose considerably in weight. This is due partly to 

 the impaired digestion of fat, in part to the direct loss of the biliary acids. If 

 dogs are nevertheless to maintain the same weight, they must consume almost 

 double their former nourishment. Under such conditions, carbohydrates are 

 especially serviceable as a substitute for fat in the diet. If their digestive ap- 

 paratus is in other respects intact, the animals may, by reason of their voracity, 

 even gain in weight. Under such circumstances, however, it is the muscles 

 almost alone and not the fat that is increased. 



The fact that bile is secreted during fetal life, while none of the 

 other digestive fluids are produced, indicates that the bile is in part a 

 product of retrogressive tissue-metamorphosis, and is intended for the 

 constant elimination of certain excrementitious matters. 



The cholic acid, which is absorbed through the intestinal wall, is finally 

 burned up in the body into carbon dioxid and water. The glycin gives rise to 

 the production of urea, as well as hippuric acid, as, after the ingestion of that 

 substance, the amount of urea is greatly increased. The fate of the taurin is 

 not known. Considerable amounts administered to human beings by the stomach 

 appear 'again in the urine principally as taurocarbamic acid, together with a small 

 amount of unchanged taurin. When injected subcutaneously into a rabbit, it 

 almost all appears in the urine. 



THE INTESTINAL JUICE. 



The human intestine is ten times as long as the length of the body from the 

 vertex to the anus. In this it resembles that of fructivorous apes. It is relatively 

 longer than that of omnivora. Its minimum length is 507 cm.; its maximum 

 length, 1149 cm. Its capacity is relatively greatest in children, in whom also 

 it is relatively longer. The intestine is somewhat longer in males than in females. 



The intestinal juice is the digestive fluid secreted by the numerous 

 glands of the intestinal mucous membrane. The largest amount is fur- 

 nished by Lieberkuhn's glands; the duodenum receives, besides, the 

 scanty secretion of the compound alveolar grands of Brunner. 



B runner's glands, which occur singly in human beings, but in the sheep 

 constitute a continuous layer in the duodenum, are present, in part, at the 

 pylorus. Their cylindrical cells have a middle, darker zone'; the flat nucleus 

 lies near the base of the cell, with a diplosome nearer its free surface. During 

 the state of hunger, the cells are turbid and small, and, like the pyloric glands 

 of the stomach, they contain fatty granules, while during digestive activity 

 they are large and clear. The glands contain nerve-filaments from Meissner's 

 plexus in the mucous membrane. 



The Secretion of Brunner' s Glands. The usually granular contents 

 of the secretory cells consist, in addition to albuminous materials, of 

 mucin and ferment-substances of unknown nature. It is not improbable 

 that these glands are related to the pancreas, and perhaps are even to be 

 regarded as detached portions of the pancreas. Their activity seems to 

 favor this view. An aqueous extract (i) dissolves albumin slowly 

 and feebly, at the temperature of the body. (2) It possesses diastatic 

 activity. The secretion appears to have no effect on fats. 



It should be especially emphasized that, as on account of the small size 

 of the glands they must be viewed individually, \vith a magnifying glass, from 

 the under surface of the intestinal mucous membrane, digestive experiments 

 are exceedingly difficult. 



Lieberkuhn's crypts or glands are simple tubular glands, resembling the finger 

 of a glove, that lie close to one another in the intestinal mucous membrane, 

 and in greatest number in that of the large intestine (on account of the absence 

 of villi). They possess a membrana propria, constituted of most delicate fibrils, 



