HUMAN FECUNDITY 108 



the recurrence of menstruation and not the condition of amenorrhoea 

 is the normal state during lactation, but that menstruation is 

 not so frequent in the later lactations as in the earlier ones. For- 

 dyce has reached similar conclusions, finding that menstruation 

 occurred during lactation in 40 per cent, of the cases in which 

 suckling was performed, while in 92 per cent, of the cases its 

 return was within nine months of parturition, and that menstrua- 

 tion during lactation was commoner with the earlier than with the 

 later lactations, showing that age is an important factor.' 1 



There is another question of importance. It may be asked 

 what influence age at marriage has upon fecundity. As far as the 

 age of the husband is concerned, there is scarcely any influence 

 at all. For any given age of wife the fecundity remains nearly 

 the same, whatever the age of the husband. The age of the wife, 

 however, is of importance, apart from the fact that delay in 

 marriage reduces the use made of the limited period of maturity. 

 For a woman is not equally fecund throughout the mature period. 

 The earlier years are the most fecund years, and therefore post- 

 ponement of marriage reduces the fecundity, other things being 

 equal, by more than the fraction of the mature period which is 

 passed in celibacy. According to Dunlop's observations on 

 marriage in Scotland ' the effect of one year's delay of marriage is 

 to reduce the average family by fully one-third of a child, or that 

 three years' delay may be expected to result in the family being 

 one child less. This result may be fairly correct in general, but 

 it cannot be strictly applied, for the crude observations show that 

 the effect of one year's delay is not constant through the fertile 

 period of the woman's life, but is greater for the younger and less 

 for the later years. Thus a year's delay when the woman is aged 

 from 20 to 25 averages 045 of a child, 0-37 when she is aged from 

 25 to 30, 0-32 when she is aged from 30 to 35, 0-29 when she is 

 aged from 35 to 40, and 0-19 when she is aged from 40 to 45.' 2 It 

 requires, it may be noticed, a delay of about forty years on the part 

 of the husband to decrease the number of children by one 

 child. 3 



v A further problem is the influence of sexual intercourse before 

 puberty upon fecundity. Exactly what influence early intercourse 

 has upon the generative organs and their functions is not clear. 



1 Marshall, loc. cit., p. 74. .See also Heape, loc. cit., p. 43, and Matthews Duncan, 

 Sterility in Women, p. 85. 2 Dunlop, J. M. S. 8. , vol. Ixxvi, p. 266. 8 Ibid., p 267. 



