1846.] Principles of Breeding. 115 



of one of the first pair, and one-fourth of the other. The next 

 O^eneration, bred in the same way, would be seven-eighths of the 

 parent, the next fifteen-sixteenths, and so on ; the blood of one of 

 the original ancestors increasing and the other diminishing in this 

 ratio with each generation. This and similar courses of breeding 

 have been aptly denominated " breeding my" and the term " close 

 breeding''^ is also more or less applicable, according to the nearness 

 of relationship existing between animals coupled together, or ac- 

 cording to the extent to which breeding in is carried. 



Having settled what is to be understood by the term " in-and- 

 in," we will proceed to consijler the expediency of that course of 

 breeding. And it may be observed in the first place, that al- 

 though many distinguished breeders have advocated and followed, 

 more or less, breeding in, or close breeding, very few, if any, 

 have recommended in-and-in breeding, as here defined* The 

 effects of the course when carried on for several generations, can 

 not perhaps be better described than in the language of Sebright, 

 in the essay above referred to. " I have," says he, " tried many 

 experiments by breeding in-and-in, upon dogs, fowls, and pigeons; 

 the dogs became from strong spaniels, weak and diminutive lap- 

 dogs; the fowls became long in the legs, small in the body, and 

 bad feeders. * * * Indeed I have no doubt but that by this 

 practice being continued, animals would, in course of time, de- 

 generate to such a degree as to become incapable of breeding at 

 all." 



It is a maxim in physics that an effect is not produced without 

 a cause. Hence it is natural to ask a reason for the ill effects al- 

 leged to be produced by in-and-in breeding. We will endeavor 

 to give one, which, though not entirely original, is in some re- 

 spects different from any we have seen offered. 



It is admitted that different families of animals have certain 

 hereditary tendencies. The proneness to particular diseases in 

 families of the huma,n race, is evidence of this. Now it is plain 

 that where two animals of the same blood and the same heredi- 

 tary tendencies, are coupled together, there would be a greater 

 liability in the progeny to exhibit any defect or disease which 

 belonged to the family, than there would be if only one of the 

 parents had this constitutional tendency. Hence we see the de- 

 fects of parents augmented in the progeny. 



This we believe to be the true cause of the degeneracy which 

 ensues from in-and-in breeding. But let us not be misunderstood. 

 It is not merely the nearness of relationship which produces these 



* It is proper to remark that breeding in when carried to a certain extent, 

 may be expected to produce re?.ults similar to those of breeding: in-and in, 

 that is, the consequences of the former will resemble those of the latter sys- 

 tem, in proportion as the blood of the animals bred together becomes simiJar. 



