620 THE PHYSIOLOGY OF REPRODUCTION 



of India this percentage is still higher. ^ Among cattle the 

 average loss from sterihty and abortion (together with mortahty 

 of calves) is estimated by Heape ^ to be at least fifteen per cent., 

 while it is shown in the report (already referred to) issued by 

 the Royal Agricultural Society on fertiUty in EngUsh sheep for 

 the year 1899, that the proportion of sterile ewes was 4-71 per cent, 

 out of a total number of 96,520, and this percentage does not 

 include the ewes which aborted (see p. 612). In view of these 

 facts, it is obvious, as Heape has pointed out, that any means by 

 which sterility in domestic animals can be checked and their 

 capacity to bear young increased, must be possessed ofi great 

 commercial value. 



The Bieth-Rate in Man , 



It is now more than a century ago since Malthus ^ advanced 

 his famous proposition that wiiereas population tends to in- 

 crease in geometrical ratio, the means of subsistence increase 

 only in arithmetical proportion. As a consequence of the 

 acceptance of that doctrine, the political economists of the 

 early Victorian period tended to see in over-population the 

 most fruitful source of pauperism, disease, and crime, and the 

 cause of increasing congestion in the future. That Malthus' 

 predictions have not been verified is a matter of common 

 knowledge, and the problem before the modern economist is not 

 how to place a check on population generally, but rather how 

 to secure that future generations shall be sufficiently recruited 

 from that section of the population which is industrially capable. 



There is abundant evidence that in most civihsed countries 

 at the present time the birth-rate (that is, the proportion of 

 the children born to the population) is tending to decrease, 

 while in some countries the actual population is diminishing. 

 This decline in the birth-rate has been made the subject of 



has been drawn to the urgent need for practical proposals on the subject with 

 a view to maintaining the horse supply of the country and arresting a state 

 of things which, if it continues, must be a source of danger. 



1 Ewart, he. cit. ^ Heape, loc. cit. 



' Malthus, An Essay on the Principles of Population, 7th edition, 

 London, 1872. 



