20 A TREATISE ON HORSE-BREEDING. 



very m-arked difference would occur in their 

 structure or habits. There is a tendency in all 

 animal life to adapt itself to the conditions 

 under which it must exist; but the change may 

 be so abrupt and complete as to overcome this 

 tendency; and, under such a condition, the race 

 would speedily become extinct, or gradually die 

 out with a few generations of sickly and en- 

 feebled descendants; but, under circumstances 

 less abrupt and unfavorable, a few might sur- 

 vive, being those individuals that, from some 

 peculiarity of organization, suffered least from' 

 the change. These animals, in their turn, would 

 reproduce the peculiarities of their race, modi- 

 fied to some extent by the new conditions 

 which environed them; and these again would 

 produce animals still better adapted to the 

 new order, until, in course of time, we should 

 have a race widely differing from the original 

 type, created or evolved by a survival of those 

 best fitted to exist under the new order of 

 things, and remoulded and refashioned by the 

 changed conditions of life. 



If we accept the commonly-received doctrine 

 of the origin of the human race that is, that 

 all mankind are descended from a common par- 

 entage we are driven to the conclusion that 

 all the differences which are so apparent in the 

 human family at the present day are the re- 

 sult of the operation of the law of adaptation 



