604 PRACTICAL PROBLEMS 



excellence rapidly and with extreme certainty. Such a sire is 

 almost surely prepotent over the dams, whatever they may be, 

 and the mathematics of mating shows that if the practice is 

 continued for six generations, but one and a half per cent of the 

 original unimproved blood will remain, as is shown in the table 

 at the bottom of page 602. 



By this we see that the unimproved blood soon becomes insig- 

 nificant and rapidly disappears. This is why it is that in the 

 early days of a breed the sixth or seventh cross is declared 

 eligible to record. 



It should be noted that if any one of these generations be 

 bred with itself (grades with grades) no progress is made. Thus 

 individuals of the second generation are one fourth unim- 

 proved, and, bred to a generation of their own kind, they will 

 still remain one fourth unimproved. By the same principle, 

 half bloods bred to half bloods will produce half bloods indefi- 

 nitely. The effects of grading cease the moment we discontinue 

 the pure-bred sire. 



Abuse of grading. The chief drawback in grading is that it is 

 likely not to be followed up. The breeder is almost certain to 

 choose some promising half or three-quarter blood for a sire 

 because he " looks as good" as a pure bred, and then by the 

 law of ancestral heredity all improvement stops except the little 

 that can be accomplished by the slow process of selection. 



Advantages of grading. For economic purposes grades may be 

 equal to pure breds, biit they are wortJiless for breeding purposes ; 

 this is the plain conclusion of what is well known of the prin- 

 ciples of breeding. Grading is cheap. By the use of a single 

 individual it secures at once something more than half of the 

 total excellence of the breed, and if followed up it will secure in 

 time, through sires alone, practically all of it. 



This is the system of breeding to be recommended to the 

 great mass of stockmen, and if it could be generally adopted 

 and followed iip it would add millions to American agriculture. 

 Every stockman knows that the great bulk of the best cattle in 

 the markets are high-grade Shorthorns and Herefords. The 

 accompanying figures surely show that the less-known Angus 

 and its close relative, the Galloway, arc equally successful for 



