202 THE FLUIDS. 



creatic fluid is reabsorbed, and therefore disappears, by the time it 

 reaches the middle of the small intestine. Other agencies are there- 

 fore required to complete the processes these two fluids, have com- 

 menced, as the food passes lower down the canal ; and these are 

 apparently supplied by the intestinal fluid alone. It appears, 

 moreover, that while bile suspends and the pancreatic fluid impedes 

 the digestion of the albuminous compounds by the gastric juice, 

 they do not at all interfere with that by the intestinal fluid. 



SECTION II. 



THE GLANDULAR SECRETIONS. 



By the glandular secretions are meant those of the true or com- 

 pound racemose glands, and whose ducts are lined by a prolonga- 

 tion from a mucous membrane. They, of course, all contain some 

 admixture of mucus, and will be described in the following order: 



I. Milk. 



II. Semen. 

 III. Glandular secretions discharged into the alimentary 



canal (saliva, bile, &c.). 

 IY. Urine. 



Y. The lachrymal fluid. 



I. MILK. 



Human milk is white, slightly translucent, colorless, of a weak 

 sweetish taste, and of an alkaline reaction. Its specific gravity is 

 between 1030 and 1034. After standing at rest for a time, a yel- 

 low layer abounding in fat (the cream) forms on the surface, while 

 the fluid below becomes specifically heavier, and of a bluish tinge. 

 It is not coagulated by boiling, but forms on its surface a film of 

 coagulated caseine mixed with fat-globules. Eennet (i. e. the mu- 

 cous membrane of the calf's stomach) coagulates it, as has already 

 been explained in connection with the properties of caseine (p. 88). 

 Exposed to a temperature somewhat above the mean, an acid is 

 developed in it, and which precipitates the caseine, constituting the 

 acid fermentation or "souring" of the milk. 



The milk secreted for the first three or four days after parturition 

 has peculiar characters, and is called colostrum. This is a turbid, 

 yellowish fluid, resembling soap and water, viscid, and strongly 

 alkaline in reaction. It contains more solid constituents than nor- 

 mal milk, and passes more rapidly into the acid fermentation. This 



