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A MANUAL OF VETERINARY PHYSIOLOGY 



about 3 pounds (1-4 kilogrammes) of solids, it represents a pro- 

 duction of solid matter during the milking year equal to that of 

 the animal's body weight. The daily loss of material during 

 lactation is made up as follows : 



Protein 

 Fat . 

 Lactose 

 Salts . 



0*85 pound (0*40 kilogramme) 

 i'25 pounds (0*56 „ 



0*85 pound (0*40 ,, 



012 „ (005 



It is evident that a generous diet is necessary, not only in order 

 to meet this loss, but to provide the needful energy for the great 

 metabolic activity occurring during secretion, and to nourish 

 the foetus. 



In the following table an analysis is given of the milk of 

 different animals : 



It will be observed that the milk of the cow, sheep, and dog, 

 is remarkable for the high percentage of fat it contains. The 

 caseinogen of mare's milk is much less than that found in the 

 cow, and more like that of the human. The milk of the dog is 

 rich in caseinogen, fat, and calcium, but poor in lactose. 



Proteins. — Under the influence of rennin, caseirogen becomes 

 insoluble, and the milk is coagulated, resulting in a clot and 

 whey. The clot or insoluble casein is now termed tyrein. Neither 

 the albumin nor the caseinogen in milk is precipitated by boiling ; 

 on the other hand, colostrum is precipitated by heating, and 

 this is due to the fact that it contains globulin. The albumin 

 of milk offers some peculiarities as compared with ordinary 

 serum-albumin, and has been termed lactalbumin. 



The Fats in milk are olein, stearin, and palmitin, and the 

 proportion of these differs in various animals. The fat is con- 

 tained within fat globules, and these form in milk a true emulsion, 

 each globule being separated by a layer of milk plasma. On 

 standing, the globules rise to the surface of the fluid and form 

 cream. By the process of churning, the emulsion is destroyed, 

 and the fat is obtained as butter. Butter consists of 68 per 



