116 



GOOD FROM CROSSING. 



Chap. XVII. 



being separated during a few generations and exposed to different 

 conditions of life. 



That evil directly follows from any 



degree 



of close inter- 

 breeding has been denied by many persons ; but rarely bv anv 



practical breeder ; and never, as far as I know, by one who has 

 largely bred animals which propagate their kind quicklv. 



physiologists attribute the evil exclusively to the 

 and consequent increase of morbid tendencies common to both 

 parents : that, this is an active source of mischief there can be 

 no doubt. It is unfortunately too notorious that men and 

 various domestic animals endowed with a wretched constitu- 

 tion, and with a strong hereditary disposition to disease, if not 

 actually ill, are fully capable of procreating their kind. Close 



interbreeding, on the other hand, 



; and this 

 augmentation of 



indicates something quite distinct 



morbid tendencies common to both parents. The evidence 



immediately to be given convinces me that it is a great law of 



nature, that all organic beings profit from an occasional cross 

 with individuals not closely related to them in blood ; and 

 that, on the other hand, long-continued close interbreeding is 

 injurious. 



Various general considerations have had much influence in 



leading me to this conclusion ; but the reader will probably rely 

 more on special facts and opinions. The authority of experi- 

 enced observers, even when they do not advance the grounds of 

 their belief, is of some little value. Now almost all men who 

 have bred many kinds of animals and have written on the 

 subject, such as Sir J. Sebright, Andrew Knight, &c., 2 have 



expressed the strongest conviction on the impossibility of long- 



continued close interbreeding. Those who have compiled works 

 on agriculture, and have associated much with breeders, such as 

 the sagacious Youatt, Low, &c, have strongly declared their 

 opinion to the same effect. Prosper Lucas, trusting largely 

 to French authorities, has come to a similar conclusion. The 

 distinguished German agriculturist 



ermann von Nathusius, 



who has written the most able 



on this subject w 



hich 



I have met with, concurs ; and as I shall have to quote from 



2 For Andrew Knight, see A. Walker, on ' Intermarriage,' 1838, p. 227. Sir J- 

 Sebright's Treatise lias just been quoted. 



. 







