303 PRINCIPLES OP BREEDING. 



only four toes. The fifth toe was inherited from a five-toed 

 variety introduced into Britain by the Romans. 



There are hundreds of illustrations along this line which 

 might be cited. Scientists no longer doubt the possibility 

 of diseases being inherited. This is a point of vital import- 

 ance to the breeder of live stock. When hereditary disease 

 makes its appearance at the time of birth it is called con- 

 genital. Where considerable time elapses before it appears 

 it is designated as a case of predisposition or a tendency to 

 disease. There are certain diseases which are transmitted 

 with greater uniformity than others, yet a predisposition to 

 almost every known form of disease is almost likely to become 

 hereditary. In this connection we will not attempt to de- 

 scribe or enumerate all the diseases which are hereditary, but 

 to notice only those which illustrate the laws of hereditary 

 transmission or that are of peculiar importance to the 

 breeders. 



Scrofula and its allies cover a large and very important 

 class of troubles which are more or less hereditary. In this 

 connection much of the trouble is due to constitutional defect 

 as indicated by a narrow, slack chest, indicating lack of vigor 

 and stamina. This is especially true in tuberculosis, which 

 is one of the most common and destructive troubles to cattle. 



Bone spavin, curbs, ring bone, navicular disease and other 

 similar troubles of the bones and joints are in most instances 

 of a hereditary nature. These troubles are very seldom 

 present at birth. They usually make their appearance before 

 the animal is six years old, or as soon as the parts in question 

 are subjected to a strain of rather severe nature, such as 

 any horse is likely to receive at hard work. 



Barrenness in animals belongs to this class and is very 

 likely to be inherited. These illustrations are but a few of 

 the large number which might be cited, still they show the 

 varied influences of this law in its relation to animal breeding. 



By the law of prepotency is meant the superior influence 

 which one particular breed of animals has over another 

 breed, or the one particular parent has over another parent 

 in transmitting its characteristics to the offspring. This is an 

 important law in the improvement of our animals. It rarely 

 happens that we find an equal mingling in the offspring of 

 the natures of both parents. For some reason or other the 

 offspring generally possesses more of the characteristics of 

 one parent than of the other. In many respects this is a 



