Kraemer: Effects of Inbreeding 



233 



tendency to albinism. From experi- 

 ments with rabbits it was decided that 

 soHd-colored animals with golden-brown 

 hair, showing occasional spots of white, 

 began to turn entirely white after the 

 fourth generation. Cornevin therefore 

 suddenly jumped to the conclusion that 

 the effects of inbreeding differed with 

 different animals, and that one could not 

 dogmatically assert, for all species, that 

 it was wholly harmless. He does not 

 specifically state whether he was select- 

 ing the strongest animals to breed from, 

 but his indorsement of inbreeding gives 

 us good reason to believe that he was 

 anxious, in his experiments, to keep the 

 two factors carefully separated. He 

 wanted to observe the results of in- 

 breeding in itself — par elle menie — and 

 not to throw additional light on the 

 well-known fact that an increased ten- 

 dency to degeneracy may take place 

 through the union of two tendencies to 

 weakness and blemishes, when consan- 

 guineous matings are made. 



MANY DIFFERENCES OF OPINION. 



It is, accordingly, a mistake to think 

 that only among us Germans is there 

 such a diversity of opinion on the sub- 

 ject of inbreeding, and it is equally 

 exaggeration to think that it is we alone 

 who are so doctrinaire in these matters. 

 In all civilized countries, the views on 

 inbreeding and hybridization used to be 

 based on the haps and mishaps of 

 experiments and actual breeding. We 

 have indeed carried on the controversy 

 about pedigree-breeding and individual 

 potency with the greatest keenness, and 

 in the side-issues of this controversy 

 inbreeding of course occupies a promi- 

 nent place. But the heart of the ques- 

 tion, whether inbreeding, in and by 

 itself, results in evil, is warmly debated 

 not only among us, but everywhere else. 

 If our old theories about blooded stock 

 were one-sided on that point, if they 

 did not sufficiently distinguish between 

 pure breeding and inbreeding, we can 

 also reproach the individual-potency 

 theory nowadays with very often being 

 too general and disregarding the various 

 aspects of the question, when it argues 

 its conception of "crossing." 



Buffon had published precepts that 



were — speaking as a breeder — simply 

 crazy, but he did not lack followers. 

 Hartmann, for example, supports him. 

 "Never," he says, "must one give to a 

 stallion mares of the same breed, nor 

 must he permit the mating of two 

 animals from the same stud. It cannot 

 be too strongly recommended that one 

 should endeavor as much as possible to 

 cross his breeds of horses." Such views 

 won the day, and they created a real 

 danger. When experienced breeders, 

 such as Wollstein, Ammon, Justinus, 

 Mentzel, von Weckherlin, and others 

 took a unanimous stand in sharp opposi- 

 tion, they performed a great service. 

 But the too wide application of their 

 own doctrines had a doubtful side. 

 Though one might apply their prin- 

 ciples, in an extensive practice of in- 

 breeding, and secure satisfactory results, 

 yet the laws underlying the whole ques- 

 tion were not properly made clear, and 

 the theorizers on pedigree-breeding did 

 not even then get a full view" of certain 

 items which we now think must be 

 considered in the technical application 

 of the principles of inbreeding, if success 

 is to be had or failure to be avoided. He 

 who started in to practice the principles 

 they laid down, often had to pay the 

 consequences. And although von Weck- 

 herlin, thinking that the prejudice 

 against inbreeding arose solely as the 

 result of experience with sheep, ques- 

 tions whether these consequences are 

 appreciable, the resiiltant careless prac- 

 tice of inbreeding was unfortunate. 



IT WORKS BOTH W'AYS. 



Computations can indeed be made, 

 that the practice led to fineness of wool, 

 but the disease — the actual failure of 

 many breeders — can also be traced very 

 easily to the same practice. The wide- 

 spread creation of definite herd-types 

 through line-breeding has led to many 

 damaging results in the sheep industry, 

 and on general princip.es we ought to 

 anticipate in all other branches of live 

 stock breeding, that the building up of 

 herds characterized by certain very 

 definite traits would have a tendency to 

 limit variation and thereby to destroy 

 the prerequisite of evolutionary pro- 

 gress. Such a feeling has naturally 



