6 THE HOUSE. 



is one of the most remarkable instances of specialisation, or 

 deviation from the usual type, in accordance with particular 

 conditions of life." 



The consideration of the varieties of the horse, which 

 have resulted from its long domestication, does not come 

 within the scope of the present work, except as far as the 

 different breeds influence the character of hybrids between 

 the horse and the other species, a subject that will be fully 

 considered in the concluding chapters on Mules and 

 Mule Breeding. 



