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The Perfian and Arabian breeds of horfes brougftt 

 into Europe, are only changed by intercopulating 

 with other breeds. The Chinefe hogs may be con- 

 tinued for ages unchanged, if no crofs be permitted. 

 Thefe h£ts are notorious, and every other fa6t upon 

 this fubjeft tends to eftablifli the fame conclufion. 



4thly. Although the fame brepd of animals appears 

 not to be liable to be changed by climate or other 

 extraneous caufes, yet it is found by experience, that 

 individuals may be found among every breed of ani- 

 mals, which, from circumftances that have hitherso 

 eluded our obfervation, and which it therefore ex- 

 ceeds our power either to accelerate or retard, may 

 be met with, which are, in fome leffer circumftances, 

 different from others, though they ftill poffefs the 

 general characierifticks of the parent breed. And fo 

 ftrong is the propenfity of nature in all cafes to pro- 

 duce its own kind, that if the individuals poffeffing 

 thefe qualities, thus, as we would fay, accidentally pro- 

 duced, whether beneficial or hurtful, be felefted and 

 put to breed with others that poffefs qualities fome- 

 what of the fame fort, it is found that the defcendants 

 of thefe felefted animals will, in general, be poffeffed 

 of the diftinguifliing peculiarity for which they were 

 fele£led in an eminent degree; though among thefe 

 alfo fome individuals will be found to have lefs of 

 it than others. And if thefe leaft approved indivi- 

 duals be baniftied from the felefted ftock; and thofe, 

 both males and females, which poffefs the wifhed-for 



quality 



