HUMAN FECUNDITY 89 



intercourse. When studying the possibihty of increasing the 

 fecundity of domestic species, attention can, as pointed out by 

 Marshall in the case of sheep,i be limited to the female. Taking 

 a broad view of the matter, it is clear that there has been no change 

 in fecundity due to any change in male reproductive power. 



There are, nevertheless, two points concerning the male which 

 we may notice before we pass to the consideration of the female. 

 First, with regard to the problem as to changes in fecundity during 

 the course of history, we shall bring forward evidence to show that 

 good conditions favour an increase in the reproductive power of 

 the mammahan female. There is reason to think that good 

 conditions have a similar effect on males. Thus among some 

 mammalian species in a state of nature there is a special ' rutting 

 season ' for the male, and it is not infrequently found that 

 in captivity the males of such species will rut all the year 

 round.2 We shall also bring forward evidence to show that with 

 improvements in conditions, sexual excitement is more easily 

 aroused and that there has been an increase in the development 

 of the generative organs, and we may note here that these observa- 

 tions apply to the male as well as to the female. As, however, any 

 increase in male reproductive capacity can have had no general 

 influence upon fecundity, we may, so far as the question of any 

 general increase or decrease in fecundity is concerned, neglect the 

 male and confine our attention to the female. 



Secondly, with respect to the influence of certain factors at 

 particular times, it is in nearly all cases the female and not the 

 male which is affected. But it may be observed that sterile 

 marriages are in part due to male sterility. Mayer estimates that 

 this is so in a third of such marriages.^ Kelly gives the result of 

 an investigation into 110 cases, of which 59 per cent, are attributed 

 to the male.^ Male sterility is due either to inborn or acquired 

 conditions. So far as sterihty due to the former is concerned, 

 there do not appear to be any grounds for thinking that it has to 

 any important extent varied from one epoch to another. So far, 

 however, as sterihty due to disease is concerned, there have been 

 in all probabihty certain changes. Gonorrhoea is perhaps the 

 most important of those diseases which bring about sterility. Of 



' Marshall, Phil. Trans. B, cxcvi, 1904, p. 77. ^ Heape, Q. J. M. 8., vol. xliv, 



p. 12. 3 Mayer, Vher Sterilitdf, p. 401. * Kelly, Medical Gynecology, 



p. 354. See also Matthews Duncan, Sterility in Women, p. 3. 



