THE BREEDING OF ANIMALS, IN GENERAL 83 



HEREDITY 



For our purpose, we will define heredity as the transmission 

 or passing down of characters from parents to offspring. We 

 have already noted two great forces underlying our breeding 

 operations ; like tending to beget like, which has to do with 

 heredity; the other the great run of variation through which 

 improvement is sought in our farm animals. On heredity all 

 successful breeding operations depend. We have just noted the 

 kinds of variation, as well as the causes that lead to their 

 appearance, and now come to the question whether and to what 

 extent such variations are hereditary or transmissible to the 

 offspring. 



The extent to which these variations are transmitted is a 

 very important matter, because variations that are not re- 

 tained are of no importance in breeding, though they may be 

 of much consequence to the individual possessing them. If 

 they are transmitted, they influence the race for good or bad, 

 depending on whether desirable or undesirable. Practical men 

 work on the supposition that these variations or so-called 

 modified characters are transmitted. All recognize the neces- 

 sity of the highest development of the individual for the specific 

 purpose for which it is intended. If one is to breed the 

 best kind of beef animals, he must unite animals of the best beef 

 strains. If one is to breed the highest class of trotting horses, 

 he must unite horses that can trot fast. If one is to 

 produce cows yielding a high milk flow, he must unite animals 

 with high records of performance. Working breeders are uni- 

 versally of this opinion. All of our improved breeds of ani- 

 mals are comparatively recent. It is difficult to see how we 

 could have secured such development in so short a time, unless 

 it came through the inheritance of modified characters. 



Inheritance of disease. — In all of the early writings on hered- 

 ity, there is much discussion on the heredity of disease, and 



