188 CYCLOPEDIA OF LIVE STOCK AND COMPLETE STOCK DOCTOR. 



The predisposition most to be guarded against in horses, is hereditary 

 disability in the bone, sinew, viscera, and especially in the sight. Defec- 

 tive sight leads to shying, fright and consequent un manageability, and is 

 therefore dangerous in the extreme, 



VII. Atavism or Breeding Back. 



In breeding, if an abnormal characteristic appears in any of the young, 

 and this is found to be valuable, it should be sedulously preserved and 

 fostered. What is called breeding back or throwing back, may occur after 

 the lapse of many years. The occasional appearance of horns in Galloway 

 cattle is a case in point. Mr. Darwin mentions the occurrence in two of a 

 litter of Essex pigs, of marks of a Berkshire cross, that had lain dormant 

 for twenty-eight years. The reproduction of a peculiarity of an ancestor, 

 near or remote, whether of form, color, mental trait or predisposition to 

 disease, is termed atavism. It is a valuable trait when good qualities are 

 thrown, and they are likely to be, if the good qualities are inherent. It 

 is to be guarded against, if the qualities transmitted are bad. Hence we 

 have laid it down as a rule : Breed to none but the best. 

 VIII. Variation and Development. 



Variation is among the rarest of the occurrences that the breeder ever 

 encounters. It is in fact not susceptible of proof that distinct and well- 

 marked variation of a race is possible. Its occurrence is probably due to 

 the throwing l)ack to some long dormant quality of a remote ancestor. 

 Wild animals do not change ; among them one is like the others. If 

 transported, they may be dwarfed in size, and acquire a more abundant cov- 

 ering of hair, while their stomachs and other organs may become modi- 

 fied to suit the changed conditions in a rigorous climate, or, with warmth 

 and abundant food they may be increased in size and general develop- 

 ment. But this is not what we understand by variation, which is not 

 some sudden change in the species. Variation is rather the departure of 

 the individual from the well-known traits of his species or family, and is due, 

 as already stated, to avatism or breeding back to some ancient ancestor, and 

 to some remote cross or mingling of blood. Species may acquire certain 

 traits by development, but the process is gradual, and when once attained 

 the traits may be perpetuated. This development is most gradual in 

 horses, somewhat quicker in cattle, yet faster in sheep, and still more so in 

 swine. Horses breed but once a year, mature the most slowly of all farm 

 animals, and rarely produce more than one young at a birth. Cattle 

 mature faster, breed younger and frequently produce twins. Sheep ma- 

 ture still faster, and often produce two or more at a birth, while swine 

 mature rapidly, breed young, and produce many at a birth. 



