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.”! 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 “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. 
