THE GENERAL ASPECTS OF ANIMAL BREEDING 451 
guide in the acquirement of that fund of practical knowledge necessary 
to successful breeding. By this time no doubt many of the facts of 
heredity which the student has learned must have suggested ideas of 
practical utility, but at the risk of stating some truths already obvious, 
a brief consideration may be given to some cardinal features which must 
be taken into account in considering the relation of genetics to animal 
breeding. These things must be known in order to make proper use of 
the principles of genetics in practical animal breeding; they are mentioned 
here in order that it may be properly understood that this text does not 
pretend to be a complete manual of animal breeding, but merely en- 
deavors to point out the fundamental relations existing between genetics, 
as a pure science, and animal breeding, the craft or art of improving 
animals and maintaining present standards of excellence. 
Foremost among the requisites of a successful animal breeder must 
be the intimate knowledge and experience that comes from actual personal 
contact with livestock. The success or failure of animal breeding opera- 
tions often depends on little things, which, if neglected, destroy eventu- 
ally all the results of the most carefully laid plans. The Bates-Duchess 
line of Shorthorns were at one time far famed for excellence of con- 
formation, but a neglected tendency to barrenness along with close 
breeding resulted eventually in the extinction of this superior line of 
Shorthorn cattle. The method of breeding employed in perfecting this 
famous family was by no means one which from its very nature from 
the beginning doomed the line to extinction; on the contrary, it is one 
which gives the greatest possible degree of success provided it is applied 
intelligently and with a full appreciation of its consequences for evil 
as well as for good. The intimate knowledge which a breeder has of 
his herd should include a knowledge of every individual init. He should 
know not only the good and bad points of the individuals but also how 
these points are related to those of their immediate ancestors. A breeder 
is on the highway to success when he is so well acquainted with the 
animals of his herd that he can tell from what immediate ancestor has 
come for instance a tendency to weakness of pastern, to a sluggish dis- 
position, or ugliness or unwillingness under strain, and similarly for the 
thousand and one things which must be taken into account consciously 
or unconsciously in all breeding operations. For minute differences as 
well as greater ones are heritable, even though as yet they have not 
been reduced to Mendelian formulation. It would be the height of 
folly for an animal breeder to call in a geneticist, however well trained, 
to map out his matings for him. The services of the geneticist can only 
be in giving the principles involved in breeding; the application must be 
left to the breeder himself, who must temper his theoretical knowledge 
with an abundant fund of practical detail. 
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