318 PRINCIPLES OF STOCK-BREEDING. 



and single males, as Mr. Tegetmeier informs me, can 

 always be purchased cheaper than females." * 



As in fowls and pigeons, the sexes are not readily 

 distinguished at an early age. Any excess in the 

 death-rate of either sex would, as in the cases already 

 referred to, have an influence on the results obtained. 



Mr. Darwin has also collected data that render it 

 highly probable that the males, at birth, predominate 

 among birds, fishes, and insects.* 



The influence of wars, famines, and epidemics, 

 upon the birth-rate of communities is well marked 

 in the statistics of population; but the direction in 

 which the influence is exerted is not always the same, 

 and in some instances is entirely unexpected. In the 

 case of wars and of severe famines the birth-rate is 

 diminished; while in famines of moderate severity, 

 and in epidemics, the birth-rate is frequently increased. 



When the birth-rate is diminished by war or fam- 

 ine for a given period, there is as a rule a decided in- 

 crease in the period following that may more than 

 compensate for the previous diminution. 



Doubleday, in his "True Law of Population," 

 says : " There are numerous instances where the oc- 

 currence of misfortune and consequent privations have 

 given families to those who were childless in their 

 prosperity ; and, as elucidating the same law, we may 

 adduce another fact, well known to medical persons, 

 which is, the extraordinary tendencies to propagation 

 evinced by both sexes when semi-convalescent, after en- 

 feebling and attenuating epidemics, such as fevers, 



1 " Descent of Man," vol. i., p. 29fr. 

 a Ibid., pp. 296-307. 



