110 DOMESTIC ANIMALS. 



tution and decreased value of the new Leicester slieep and 

 the short-horned beasts. It has therefore become a kind of 

 principle with the agriculturist to effect some change in his 

 stock every second or third year; and that change is most 

 conveniently effected by introducing a new bull or ram. These 

 should be as nearly as possible of the same sort, coming from 

 a similar pasturage and climate, but possessing no relationship, 

 or at most a very distant one, to the stock to which he is in- 

 troduced." These remarks apply to all descriptions of live- 

 stock. In cattle, as well as in the human species, defects of 

 organization and permanent derangements of function obtain, 

 and are handed down when the relationship is close. 



III. CEOSSING. 



It is by judicious crossing of breeds that some of our best 

 varieties of domestic animals have been obtained. A cross 

 between a superior and an inferior breed results in a progeny 

 superior to the latter, and, for a particular use, climate, or 

 locality, often better than the former. Thus the cross between 

 the English thorough-bred horse and the inferior mare of the 

 common breed of New England gave us the Morgan breed, 

 which for all the common purposes for which a horse is used 

 is superior to the thorough-bred animal himself. 



In breeding from stock with qualifications of different descrip- 

 tions and in different degrees, the breeder will decide what are 

 indispensable or desirable qualities, and will cross with animals 

 with a view to establish them. His proceeding will be of the 

 "give-and-take" kind.' lie will, if necessary, submit to the in- 

 troduction of a trifling defect in order that he may profit by a 

 great excellence ; and between excellences perhaps somewhat 

 incompatible he will decide which is the greatest, and give it 

 the preference. 



The following account of the way in which the new French 

 breed of sheep, La Chamois, was originated, throws light upon 

 an important principle in breeding; namely, that the influence 

 of the male upon the offspring will be the stronger the purer 



