612 GENETICS IN RELATION TO AGRICULTURE 



cattle. Here questions of the regularity of breeding, of the type of 

 cow best suited for the production of young, of the ability of cows to 

 provide sufficient nourishment for their offspring, of adaptability to 

 the conditions of climate and to the other environmental features of 

 the locality in which they are produced, and many other considerations 

 enter in. Finally we have the ideal breed type to consider: the animal 

 must possess those characters which distinguish Shorthorns as a breed 

 from other beef breeds such as Aberdeen Angus, Galloway, or Hereford 

 cattle; and very likely it will be necessary in order for it to meet with 

 favor that it display those particular characteristics of the Shorthorn 

 breed which mark it as belonging to some favorite family or strain. 

 We have seen how difficult it is to deal with Mendelian experiments 

 involving differences in five or six definite, allelomorphic pairs of factors ; 

 how much more difficult must it be to deal with all the variable considera- 

 tions which enter into the discussion of the method of constructing an 

 ideal beef- type of Shorthorn cattle. And yet even in the face of all 

 these requirements the results of intelligent, systematic breeding opera- 

 tions are surprising in excellence and uniformity of product. When we 

 consider this fact we can only become more strongly convinced of the 

 definite, knowable operation of the laws of heredity. 



But these factors which enter into the determination of ideal types 

 are largely considerations outside the pale of genetics proper. These are 

 the matters which must be added to a knowledge of genetics in order to 

 complete the equipment which would be at the command of the animal 

 breeder. To this knowledge, also, must be added information bearing 

 on the technique of managing breeding herds in order to realize the full 

 returns which it should be possible to secure. This information will 

 include a large and varied range of topics such as the methods of feeding 

 breeding stock and of developing young stock, the determination of the 

 proper number and use of service animals, methods of coping with disease 

 of various kinds; a knowledge of methods and appliances by which the 

 greatest possible use may be made of particularly excellent animals, such 

 as by artificial insemination, and a thousand and one items to recount 

 which would only make this discussion more tedious and uninteresting. 

 But these elements are none the less essential to the equipment of the 

 successful animal breeder. 



So we come to the end of our account of genetic principles in animal 

 breeding, realizing very keenly the limitations in our knowledge, and 

 the inadequacy of the principles of genetics alone and unsupported to 

 serve as a working equipment for the practical animal breeder. But we 

 take a deal of courage and satisfaction out of the fact that a consideration 

 of those principles has a proper and important part to play in animal 

 breeding, first by the emphasis which it lays upon heredity as a factor 



