SYSTEMATIC IMPROVEMENT OF ANIMALS 179 



Longhorns of middle England, with which they came into com- 

 petition in the show ring. All this was a hundred years ago, but 

 the two strains or " breeds" are becoming more, rather than less, 

 distinct because each is being selected to its own type, thus still 

 further emphasizing its distinctive characters. No good stock- 

 man would now think of mixing them, so that everything keeps 

 them apart, while nothing brings them together. Under con- 

 ditions such as these the breeds become more distinct and their 

 characters more fixed year by year. 



In a similar way southwest England developed the Devons ; 

 southeast England the Norfolk and Suffolk, now known as the 

 Red Polled ; and Scotland developed the Ayrshire, Galloway, 

 and Aberdeen Angus. 



Horses, sheep, and swine, dogs, cats, and even pigeons, — in- 

 deed, all other domesticated animals, — have, in much the same 

 way, developed a variety of favorite strains which in time come to 

 be recognized as breeds, and the individuals of such distinct strains 

 are spoken of as " pure breds." 1 Thus arose the so-called pure 

 breeds, whose purity of blood is seen to be relative rather than 

 absolute, for all of them when traced far enough back M run into 

 the woods," that is, merge into the common stock of the region 

 out of which they arose by methods here but briefly outlined. 



Pedigree registers. It is manifest that the early breeders ex- 

 perienced much difficulty in determining purity of blood and in 

 avoiding the use of individuals of mixed or impure blood lines, 

 nor is it difficult to understand the necessity of some recognized 

 record as the ultimate authority. The number of animals that any 

 breeder might personally know to be pure would be exceedingly 

 limited. Again, the purer the blood the more the animal is worth, 

 other things equal ; and the temptation for unprincipled stockmen 

 to claim purity of blood for mixed animals is clearly extreme. 



1 The word " thoroughbred " is sometimes erroneously used to designate 

 such animals. This term is the breed name of the English running horse and 

 should never be used as synonymous with pure bred. Thus we can have a 

 pure-bred cow, but a thoroughbred is a horse, and a running horse at that. 



