COLOSTRUM 301 



liquid secreted, after parturition, is so different from ordinary milk that 

 it has been called by another name. It is then known as colostrum, the 

 peculiar properties of which will be considered under a distinct head. 

 As the secretion of milk becomes established, the liquid, from the first 

 to the fifteenth day, gradually becomes diminished in density and in its 

 proportion of water and of sugar, while there is a progressive increase 

 in the proportion of most of the other constituents butter, casein 

 and the inorganic salts. The milk, therefore, so far as one can judge 

 from its composition, as it increases in quantity during the first few 

 days of lactation, is constantly increasing in nutritive properties. The 

 differences in the composition of the milk, taken from month to month 

 during the entire period of lactation, are not so distinctly marked. It 

 is difficult, indeed, to indicate any constant variations of sufficient im- 

 portance to lead to the view that the milk varies much in its nutritive 

 properties at different times during the ordinary period of lactation. 

 The differences between the milk of primiparae and multiparae are 

 slight and unimportant. As a rule, however, the milk of primiparae 

 approaches more nearly the normal standard. 



In normal lactation there is no marked and constant difference in 

 composition between milk that has been secreted in great abundance 

 and milk produced in comparatively small quantity ; and the difference 

 between the liquid first drawn from the breast and that taken when the 

 ducts are nearly empty, which is observed in the milk of the cow., has 

 not been noted in human milk. 



COLOSTRUM 



Near the end of utero-gestation, during a period which varies con- 

 siderably in different women and has not been accurately determined, 

 a small quantity of a thickish stringy liquid frequently may be drawn 

 from the mammary glands. This bears little resemblance to perfectly- 

 formed milk. It is small in quantity and usually is more abundant in 

 multiparae than in primiparae. This liquid, as well as that secreted for 

 the first few days after delivery, is called colostrum. It is yellowish, 

 semiopaque, of a distinctly alkaline reaction and is somewhat mucilagi- 

 nous in consistence. Its specific gravity is considerably above that of the 

 ordinary milk, being between 1040 and 1060. As lactation progresses, 

 the character of the secretion rapidly changes, until the liquid becomes 

 filled with true milk-globules and assumes the characters of ordinary 

 milk. 



The opacity of the colostrum is due to the presence of a number of 

 different corpuscular elements. Milk-globules, variable in size and 

 number, are to be found in the secretion from the first. These, how- 



