INBREEDING. 95 



who continued to follow in-and-in breeding for 

 a long period of years. Were it necessary in- 

 stances drawn from the early history of most 

 of our improved breeds could be cited showing 

 the predominant influence of one or two early 

 bulls on the race history. 



Nor has it been otherwise in the history of 

 improvement in other animals. Some of the 

 more fastidious breeders of the Thoroughbred 

 race horse insist that every animal must trace 

 in every line to an oriental source. As only 

 comparatively few Arabs and Barbs were ever 

 imported into England such pedigrees when 

 fully extended would exhibit a great converg- 

 ence as the further end was reached. Such a 

 diagram would be very remarkable, as the 

 theory on which the Thoroughbred has been 

 all but universally bred is one of avoiding 

 anything approaching close breeding, so that 

 a rapid expansion of blood-lines followed the 

 earlier and necessary close breeding. In many 

 varieties of Bantam fowls in-and-in breeding 

 has always been resorted to; indeed, it has been 

 found almost impossible to maintain the very 

 small size of these fowls where they are not 

 constantly closely interbred. The same is true 

 of many varieties of a toy" pigeons, the tiny 

 size being maintained by the most constant 

 return to a single line of blood mating brother 

 and sister, and similar cases of incestuous 

 crosses. 



