610 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



resembles blood-serum, with the addition of colostrum corpuscles. 

 Gradually, however, the colostrum secretion passes into a milk secretion, 

 albumen and colostrum corpuscles become reduced in amount, fat, casein, 

 sugar, and milk-globules increase. The specific gravity of colostrum 

 varies from 1040 to 1060, being higher immediately after delivery and 

 falling as it gives place to a true milk secretion. Thus, according to 

 Quevenne, the specific gravity of colostrum of the cow on the first day 

 after calving is 1060; on the second, 1053; on the third, 1035; on the 

 fourth, 1040 ; on the fifth, 1027. The reaction of colostrum is ordinarily 

 alkaline and becomes acid on standing. Immediately after calving the 

 colostrum of the cow contains 8.5 per cent, albumen, after one day 6.4 

 per cent., after three clays 3.4 per cent., after seven days 1.9 per cent., 

 and after twenty-one days 0.6 per cent. On an average, colostrum may 

 be said to have the following composition : — 



Water, . ... 78.7 per cent. 



Casein, ... . 7.3 " 



Albumen, . . . . 7.5 " 



Fats, . ... 4.0 " 



Sugar, . ... . 1.5 " 



Salts. . . 1.0 " 



The so-called uterine milk is a white or rose-colored, creamy, alkaline 

 fluid, with specific gravity of 1030 to 1040, and is obtained by compres- 

 sion of the placental cotyledons of ruminant animals. It rapidly 

 becomes acid and undergoes spontaneous coagulation. It contains fatty 

 particles, free nuclei, and epithelial cells. The following table represents 

 its composition in the cow : — 



Water, . . . 87.91 per cent. 



Solids, . . . . 12.09 " 



Fats, . . . 1.23 



Albumen cells, . . . 10.40 " 



Albuminates, . . . 0.16 " 



Ash, .... . 0.37 



1. The Physical and Chemical Properties of Milk. — Milk is an 

 opaque fluid, with a sweetish taste and an opalescent bluish tint, in thin 

 layers, and a characteristic odor due to the volatile substances derived 

 from the secretions of the cutaneous glands. 



Milk is not a homogeneous fluid, but is an emulsion, which consists 

 of the so-called milk-globules suspended in milk-plasma, the latter con- 

 sisting of a solution of albumen, sugar, and salts. Examined under the 

 microscope the milk-globules appear as highly refractive drops of oil 

 floating in the clear fluid (Figs. 258 and 259). 



The size of these globules varies from 0.01 to 0.03 millimeter. 



In colostrum the corpuscles are much larger than in milk, and are 

 capable of amoeboid movements. The milk-corpuscles consist almost 



