188 FUNCTIONS OF NUTRITION. 



This substance is often considerably more abundant in the portal blood 

 than in that taken from the general venous system. It resembles the 

 biliary matters in consistency, and dissolves, like them, with great 

 readiness in water ; but in no instance have we obtained from it a 

 characteristic reaction with Pettenkofer's test. This is not because the 

 reaction is masked by other ingredients of the blood ; for if, at the 

 same time, bile be added to blood taken from the abdominal vena cava, 

 in the proportion of one drop of bile to seven or eight cubic centimetres 

 of blood, and the two specimens treated alike, the ether-precipitate may 

 be considerably more abundant in the case of the portal blood ; and yet 

 that from the blood of the vena cava, dissolved in water, will give Pet- 

 tenkofer's reaction perfectly, while that of the portal blood will yield 

 no such reaction. 



The bile, accordingly, is a secretion which has not yet accomplished 

 its function when secreted and poured into the intestine. Although its 

 most abundant discharge coincides with the beginning of digestion, it 

 does not seem to aid the operation of the digestive fluids, but rather to 

 be itself acted on by them, and converted into other forms of combina- 

 tion. The intestine is, therefore, for the biliary ingredients, a place of 

 passage, where they undergo an intermediate transformation between 

 their production in the liver and their final disappearance in other parts. 

 It is still unknown what new substances are produced by these changes ; 

 but they seem to be essential for general nutrition, which cannot be long 

 maintained if the biliary matters are permanently withdrawn from the 

 system. 



Intestinal Juice. 



The secretory apparatus of the small intestine consists of two sets 

 of glandular organs; .first, Brunner's glands, which are lobulated 

 glandules, confined to the upper part of the duodenum, for a distance 

 of several centimetres from the pylorus ; and, secondly, the follicles of 

 Lieberkuhn, which are simple tubular glandules, occupying the sub- 

 stance of the mucous membrane for the whole length of the small in- 

 testine. 



FIG. 30. 



-Of 



,/ // ' 



e 



LONGITUDINAL SECTION OF WALL OF DUODENUM IN THE DOG ; showing the submucous layer of 

 Brunner's Glands. a. Mucous membrane. 6. Layer of submucous connective tissue, in which the 

 glands are situated, c. Muscular coat. d. Peritoneal coat. e. Brunner's glands, with their ducts 

 opening on the free surface of the mucous membrane. (Bernard.) 



Brunner's glands, or the duodenal glandules, are situated in the sub- 

 mucous layer of connective tissue in the duodenum. They are spheri- 

 cal, or, when thickly set, irregularly polygonal in shape from mutual 

 pressure, and from ^ to 1 millimetre in diameter. 



In structure, they resemble the lobulated glandules of the mouth, 



