Kraemer: Effects of Inbreeding 



229 



degeneracy is also of great interest. One 

 reads so much on this question without 

 getting a distinct impression, that a real 

 proof for the degenerative effects of 

 inbreeding seems to be obscured by the 

 very form in which it is presented. 

 Darwin went into the question of deer 

 at some length, and he finally comes to 

 the general conclusion that continued 

 interbreeding here, too, leads to harm. 



"As some of our British parks are 

 ancient," he says, "it occurred to me 

 that there must have been long-con- 

 tinued close interbreeding with the 

 fallow deer (Cervus dama) kept in them; 

 but on inquiry I find that it is a com- 

 mon practice to infuse new blood by 

 procuring bucks from other parks. Mr. 

 Shirley, who has carefully studied the 

 management of deer, admits that in 

 some parks there has been no admixture 

 of foreign blood from a time beyond 

 the memory of man. But he concludes 

 'that in the end the constant breeding 

 in-and-in is sure to tell to the disadvan- 

 tage of the whole herd, though it may 

 take a very long time to prove it ; more- 

 over, when we find, as is constantly the 

 case, that the introduction of fresh 

 blood has been of the very greatest use 

 to deer, both by improving their size 

 and appearance, and particularly by 

 being of service in removing the taint 

 of "rickback" if not of other diseases, 

 to which deer are sometimes subject 

 when the blood has not been changed, 

 there can, I think, be no doubt but that 

 a judicious cross with a good stock is of 

 the greatest consequence, and is indeed 

 essential, sooner or later, to the pros- 

 perity of every well-ordered park.' " 



In referring to the longhorns of 

 Bakewell, Darwin also takes the view 

 adopted by Youatt. Continued in- 

 breeding led in this case to a weakness of 

 constitution not compatible with good 

 management, and reproduction became 

 uncertain. At the very commencement, 

 however, Darwin naturally mentions 

 the Shorthorns, among which the most 

 extended use of inbreeding was notori- 

 oush^ made. So, says Darwin, "the 

 famous bull Favourite (who was himself 

 the offspring of a half-brother and sister 

 from Foljambe) was matched with his 

 own daughter, granddaughter and great- 



granddaughter, so that the produce of 

 this last union, or the great-great- 

 granddaughter, had 15-16ths or 93.75% 

 of the blood of Favourite in her veins. 

 This cow was matched with the bull 

 Wellington, having 62.5% of Favourite 

 blood in his veins, and produced 

 Clarissa ; Clarissa was matched with the 

 bull Lancaster, having 68.75% of the 

 same blood, and she yielded valuable 

 offspring." 



RESULTS WITH SHORTHORNS. 



The numerous examples from Short- 

 horn herds show that consanguineous 

 breeding of a very wide extent may be 

 practiced without leading to the extinc- 

 tion of a herd. They do not show, how- 

 ever, that continuous inbreeding is in 

 general uninjurious. Darwin himself 

 well shows that even Collins practiced 

 crossing. And while Bates, that success- 

 ful breeder, practiced close inbreeding 

 for 13 years, and had, as Darwin re- 

 marks, "the most exalted idea of the 

 value of his herd," yet during the next 

 17 years he was obliged three times to 

 introduce new blood into it. Bates 

 himself said, according to Darwin's 

 account, "that to breed in-and-in from 

 a bad stock was ruin and devastation; 

 yet that the practice may safely be 

 followed within certain limits when the 

 parents so related are descended from 

 first-rate animals." 



With sheep also, according to Darwin, 

 inbreeding has been much practiced. 

 Messrs. Brown are said never to have 

 introduced new blood into their 

 Leicesters during 50 years, and we have 

 of course no right to question the truth 

 of the breeders' statements in such 

 instances. Mr. Barford, in the course 

 of a half century, had come to the con- 

 clusion that inbreeding did no harm, if 

 practiced on animals quite sound in 

 constitution, but on the other hand he 

 does not claim to have practiced breed- 

 ing in the closest degrees of affinity. 

 He adds, however, that most great 

 breeders of sheep have protested against 

 continued close interbreeding. Jonas 

 Webb is said to have kept five separate 

 families, to work on, in order to retain 

 the requisite distance of relationshJ]j 

 between the sexes. 



