44 WALTER HEAPE. 



the same is probably true for the Greenland musk ox 

 (Lydekker, 1898) ; while the walrus, which goes nearly 

 twelve months with young, uurses her calf or provides it 

 with food for two years (Bell, 1874), and duriug that time 

 anoestrum appears to persist. 



Similar evidence of variation is to be found in the human 

 female. Among the Esquimaux in high latitudes children 

 are nursed from four to six years, and women bear children 

 about every four years (Cook, 1894). It is not uncommon to 

 hear of women of various tribes purposely prolonging the 

 nui-sing period in order to avoid too frequent breeding. The 

 Waganda women nurse their children until two years of age, 

 and live apart from their husbands from the time of con- 

 ception until the child is weaned (Felkin, 1885). The 

 Andaman Island native women nurse their children as long as 

 they can (Man, 1882). On the other hand, it is recorded 

 that among the North-west Central Queensland natives 

 nursing may go on for three, four, or five years, and a mother 

 is frequently seen with two children of different ages at the 

 breast (Roth, 1897). Among more civilised women menstrua- 

 tion is frequently in abeyance during the nursing period, 

 nevertheless many women menstruate while lactation is still 

 possible. Such a possibility is not confined to women among 

 menstruating animals. I have seen a monkey, Macacus 

 cynoraolgus, in the gardens of the Zoological Society at 

 Calcutta, which menstruated regularly while still suckling a 

 young one. 



The whole question of lactation and its relation to sexual 

 phenomena, more especially gestation, is of great interest, 

 all the more perhaps when it is remembered that virgin 

 bitches frequently secrete milk in sufficient quantities to 

 interfere with their work (foxhounds), while mules have 

 been known to nurse successfully the foal of a mare ; but for 

 our present purpose sufficient has been said, and in conclusion 

 it may be argued that when nursing encroaches upon the 

 sexual season, the recurrence of the latter depends upon the 

 vigour of the mother and her powers of recuperation. 



