282 PHYSIOLOGY AT THE FARM. 



also in their extremities, where the milk is secreted, the epi- 

 thelium presents the form of cells. The duct is strengthened 

 and rendered elastic by fibrous and elastic yellow tissue placed 

 externally to the mucous membrane. Near the external ter- 

 minal portion the same tissue becomes more and more de- 

 veloped, restricting the opening, so that no milk can escape 

 from the teat unless by suction, or by -pressure from above. 

 It is owing apparently to a defect in the development of the 

 fibrous tissue at the end of the teat that some cows lose the 

 milk as soon as the reservoirs and ducts become full. The 

 popular idea that the udder of a cow consists of four quarters, 

 each of which is independent of the others, is correct, as re- 

 presenting what was stated above namely, that there are 

 usually four glands in the mamma of the cow, to each of 

 which corresponds a teat, and also a reservoir for the milk 

 immediately above its upper extremity. 



Woman's milk is generally of a more bluish-white colour 

 than that of the cow or other animal, and is likewise sweeter 

 in flavour. Its reaction is strongly alkaline, and it has less 

 tendency to become acid than other kinds of milk. Its specific 

 gravity ranges between 1.030 and 1.034, and the proportion of 

 solid constituents varies from 11 to 13 per cent, while among 

 these there are on an average 3.5 per cent of caseine and 4 to 

 6 of sugar. The caseine in woman's milk is not so completely 

 precipitated by acids and by rennet as in the case of cows' 

 milk; the coagulum, moreover, is somewhat gelatinous, and not 

 so dense and solid, and is therefore more easily dissolved in 

 the child's stomach. The butter of woman's milk is supposed 

 to have a larger proportion of oleine than that of cows' milk. 



Cows' milk is nearly pure white, or verging somewhat to a 

 yellowish-white colour. Its specific gravity ranges between 

 1.026 and 1.035. The proportion of solid constituents varies 

 between 12.9 and 16 per cent. The caseine is in larger pro- 



