376 SECRETION. 



in its proportion of water and of sugar, while there is a progressive increase in the pro- 

 portion of most of the other constituents, viz., butter, caseine, and the inorganic salts. 

 The milk, therefore, as far as we can judge from its composition, as it increases in 

 quantity during the first few days of lactation, is constantly increasing in its 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 importance 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 noted between the milk of primiparas and multipart were very slight and 

 unimportant. As a rule, however, the milk of primiparse approaches more nearly the 

 normal standard. 



The menstrual periods, when they occur during lactation, have been found by most 

 observers to modify considerably the composition and properties of the milk ; and it is 

 well known to practical physicians that the secretion is then liable to produce serious 

 disturbances of the digestive system of the child, although frequently these effects are not 

 observed. The changes in the composition of the milk which commonly occur during 

 menstruation are, great increase in the quantity of caseine, increase in the proportion of 

 butter and the inorganic salts, and a slight diminution in the proportion of sugar. The 

 common impression that the milk is unfit for the nourishment of the child if pregnancy 

 occur during lactation is undoubtedly well-founded, although analyses of the milk of 

 pregnant women have never been made upon an extended scale. 



In normal lactation, there is no marked and constant difference in composition between 

 milk that has been secreted in great abundance and milk which is produced in compara- 

 tively small quantity ; nor do we observe that difference between the milk first drawn 

 from the breast and that taken when the ducts are nearly empty, which is observed in 

 the milk of the cow. 



The influence of alimentation and the taking of liquids upon lactation relates chiefly to 

 the quantity of milk and has already been considered. 



In treating of the influences which modify the secretion of milk, we have already 

 alluded to the effects of violent mental emotions upon the production and the composition 

 of this fluid. The very remarkable case of profound alteration of the milk by violent 

 grief, detailed by Vernois and Becquerel, is the only one in which the secretion in this 

 condition has been carefully analyzed. The changes thus produced in its composition 

 have already been referred to, the most marked difference being observed in the propor- 

 tion of butter, which became reduced from 23*79 to 5'14 parts per 1,000. 



Colostrum. 



Near the end of utero- gestation, during a period which varies considerably in different 

 women and has not been accurately determined, a small quantity of a thickish, stringy 

 fluid may frequently be drawn from the mammary glands. This bears little resemblance 

 to perfectly-formed milk. It is small in quantity and is usually more abundant in multi- 

 part than in primiparso. This fluid, with that secreted for the first few days after 

 delivery, is called colostrum. It is yellowish, semiopaque, of a distinctly alkaline reaction, 

 and is somewhat mucilaginous in its consistence. Its specific gravity is considerably above 

 that of the ordinary milk, being from 1040 to 1060. As lactation progresses, the charac- 

 ter of the secretion rapidly changes, until it becomes loaded 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 cor- 

 puscular elements. Milk-globules, very variable in size and number, are to be found in 

 the secretion from the first. These, however, do not exist in sufficient quantity to render 

 the fluid very opaque, and they are frequently aggregated in rounded and irregular 

 masses, held together, apparently, by some glutinous matter. Peculiar corpuscles, first 



