4IO FEEDING FARM ANIMALS 



only in milk. Milk sugar has not been met with else- 

 where in the animal organism. The ash of milk contains 

 from three to five times as much potash as soda, while the 

 ash of blood contains from three to five times as much 

 soda as potash. Milk, therefore, cannot be a secretion, in 

 the ordinary use of the term. Moreover, milk contains 

 within itself all the essential constituents for sustaining 

 animal life and in due balance which is not true of blood. 



Milk is secreted in the mammary glands. It is formed 

 in the milk glands and from the cells of the same. That 

 its formation shall be possible, it is essential that the ani- 

 mal which has not heretofore produced it shall become 

 pregnant. When conception takes place, the cells begin 

 to enlarge and to fill with fat globules. New cells also 

 are formed, a process which increases until the birth period, 

 at which time it becomes very rapid. The secretions first 

 formed are those also first drawn from the udder, and 

 form the colostrum of milk (see p. 411). In three or four 

 days, this is followed by the true milk. After a period in 

 lactation, the glands decrease in size, and the milk flow is 

 reduced, hence the necessity for recurring periods of 

 pregnancy to secure corresponding periods of abundant 

 milk production. 



Milk elaboration does not proceed at a uniform rate 

 between milkings. It is most rapid by far while the milk 

 is being withdrawn. It is greatly accelerated by the manip- 

 ulation of the udder in the act of milking, and is also much 

 influenced by the nervous condition of the cow. The char- 

 acter of the manipulation exerts an important influence 

 as well as the fact of the same, as is shown from the in- 

 crease or decrease which frequently results from a change 

 of milkers. The results from nervous influence are shown 

 in the marked difference in quantity and to some extent in 

 the quality of milk withdrawn by those whose work is 

 gentle and kind, as compared with the same withdrawn 

 by milkers harsh and rough. 



That the quantity and quality of the milk are not 

 dependent entirely on the food, is evidenced in the great 



