No. 112.] 299 



The observation of many practical men might be cited to show 

 that these and and similar consequences often follow in-and-in 

 breeding. But are they the positive and necessary results of that 

 course? Does iu-and in breeding, per se. tend to degeneracy, oris 

 there a natural iaw to that effect ? 



The philosophy of the case appears to be this. Domestic ani- 

 mals are subject to certain diseases or defects, which are trans- 

 missible hereditarily. If two animals having an equal tendency 



to tlic Saine dcicOL ixiki uiiilea, the liability 01 tiife unSpring tO poS- 



sess the defect is doubly greater than if the tendency had only 

 existed in one of the parents. This consequence does not follow 

 merely because the animals are related, but because they have 

 similar defects. For example, ditferent families of cattle are 

 hereditarily prone to diseases of the lungs, and also of the liver 

 and other organs. Now if two animals are brought together 

 which are entirely unrelated, but each possessing an equally 

 strong tendency to the saaie diseases, there is no reason "why the 

 same result should not as certainly follow^ in the off>pring, as if 

 the parents had belonged to the same family. Eut it should be 

 rememberel that the constitutional tendencies of animals of the 

 same family are generally similar, and that the same defects in 

 animals of remote affinity are less frequent, so that in the ordi- 

 nary course of breeding, the danger of propagating defects is 

 greater with animals near akin, than with those more distant. 



Such seems to be a reasonable explanation of the consequences 

 "which sonutimes f>llow breeding irom domestic animals of near 

 affinities. It does not appear tiiat degeneracy is the inevitable 

 result ('f tliis course. In a state of nature, it is more than pro- 

 bable that animals of t!ic closest allinitits fre(piently interbreed 

 "witlK'Ut ail} injuri(»us result. In fact we are not without ex- 

 amples of afiimals having been bred in dnnu-stic state, directly 

 in-and-in, for many generations, waliour the hast deterioration. 

 Breeders of pigeon?? have n<itieed tliat the two hatched in the 

 same nest at the same time, are usually male arid teniale, and tliat 

 they generally pair and breed together. CI. Jaqu€S,of the Ten- 

 Hills P^lrm, near Boston, imported one pair of Bremen geese from 

 Germany, in 1822. It would be difficult to enumerate the num- 



