REPRODUCTION 581 



In a healthy woman, not suckling her child, ovulation and 

 menstruation recommence about six weeks after childbirth; a 

 nursing mother usually does not menstruate for ten or twelve 

 months; the infant should then be weaned. 



When an infant cannot be suckled by its mother or a wet-nurse 

 an important matter is to decide what is the best food to substi- 

 tute. Good cow's milk contains rather more fats than that of a 

 woman, and much more casein; the following table gives averages 

 in 1,000 parts of milk: 



Woman Cow 



Casein 28.0 54.0 



Butter 33.5 43.0 



Milk-sugar 44.5 42.5 



Inorganic matters 4.75 7.75 



The inorganic matters of human milk yield, on analysis, in 

 100 parts calcium carbonate, 6.9; calcium phosphate, 70.6; 

 sodium chlorid, 9.8; sodium sulphate, 7.4; other salts, 5.3. The 

 lime salts are of especial importance to the child, which has still 

 to build up nearly all its bony skeleton. 



When undiluted cow's milk is given to infants they rarely bear 

 it well; the too abundant casein is vomited in loose coagula. The 

 milk should therefore be diluted with half or, for very young 

 children, even two-thirds its bulk of water. This, however, brings 

 down the percentage of sugar and fat below the proper amount. 

 The sugar is commonly replaced by adding cane-sugar; but sugar 

 of milk is readily obtainable and is better for the purpose. If 

 used at all it should, however, be employed from the first; it 

 sweetens much less than cane-sugar, and infants used to the latter 

 often refuse milk in which milk-sugar is substituted. In order to 

 bring the percentage of fat up to normal it is usual to dilute, not 

 " whole milk" but "top milk." The latter, after the milk has 

 stood for a few hours, contains enough of the rising cream to 

 supply the needed fat. As the infant grows older less diluted 

 cow's milk may gradually be given; after the seventh or eighth 

 month no water need be added. 



It should not be necessary to emphasize the vital importance of 

 giving to infants only the purest milk obtainable. It is. unfor- 

 tunately true that the milk produced in the average dairy is not 



