SECTION IX. 

 The Mammary Secretion. 



The milk is the secretion of the mammary glands of the females of 

 the mammalian group, and is poured out, as a rule, only in the last 

 stages of pregnancy and after the birth. Sometimes, especially in 

 goats, the secretion of milk is formed by the rudimentary glands of the 

 male. In many cases the mammary glands of newly-born infants of both 

 sexes also pour out a scanty secretion, which is, probably, closely similar 

 in composition to milk, although it has been but slightly investigated. 

 This secretion commences usually three or four days after the birth, 

 increases up to the eighth day, remains a few days stationary, and then 

 commences to decrease, and by the end of the first month has usually 

 entirely disappeared. 



The mammary glands of various animals of the mammalian type 

 also frequently pour out a secretion immediately after birth. These 

 facts, as well as the morphological characters of the mammary gland, 

 indicate that they are exceptionally developed sebaceous glands ; the 

 close similarity in composition of the milk and the secretion of the 

 sebaceous glands of the skin also supports this view. 



The following table represents the composition of this secretion 

 from the rudimentary mammary gland : — 



"Water, .... 

 Solids, 



Newly-Born Five-weeks 

 Infant. old Foal. 



. 95.705 93.10 

 4.295 6.90 



Casein, 

 Albumen, 

 Fat, 



Milk-sugar, 

 Inorganic salts, . 



0.557 0.50 

 0.490 1.02 

 1.456 (?) 

 . 0.956 3.67 

 0.826 0.44 



Before and shortly after delivery pregnant females secrete a fluid 

 from their mammary glands which differs considerably from that of the 

 later secretion. It is termed colostrum. 



Colostrum is an opaque, yellowish fluid, containing a large amount 

 of the so-called colostrum cells (true glandular cells in different stages 

 of fatty degeneration), few milk-globules, a large amount of albumen, 

 little or no casein, and but little fat, milk-sugar, and salts. On account 

 of its large percentage of albumen, it coagulates when heated, differing 

 in this respect from milk; in fact, colostrum when first secreted closely 



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