226 ZOOLOGICAL ACCEPTATION OF 



the effect will of course be measured by the intensity and 

 duration of the cause. 



The degree of domestication is very various. In some 

 cases the animals do not breed in servitude ; consequently 

 each individual must be reduced from the original wild state ; 

 here no variation occurs. The elephant affords an example. 

 The rein-deer is confined within narrow limits, as to tem- 

 perature; and, since it cannot be removed from these, it 

 varies little. 



There are degrees of domestication dependent probably on 

 original capabilities of education. The cat, which is only 

 partially enslaved, merely varies in the texture and colour of 

 its fur ', and inconsiderably in size : but the skeleton of any 

 tame eat differs from that of the wild in no essential point. 



The greatest differences are produced when man regu- 

 lates the sexual intercourse of animals : by selecting indivi- 

 duals to breed from, he can effect the most surprising 

 changes In form and qualities ; as the examples of the pig, 

 sheep, horse, cow and dog, will abundantly evince. The 

 deviation has become at last so great, that the original stock 

 from which the animals descended is doubtful. 



The herbivorous domestic animals, following us into all 

 climates, and governed by us in their food, labour, and ex- 

 ternal defence or protection, exhibit variations which, al- 

 though apparently very considerable, are chiefly superficial. 

 The size, the greater or less developement or entire want 

 of horns, the nature of the hairy covering, and such other 

 points, are the subjects of change. The skeleton, the form 

 and connexions of the bones, the teeth, are never altered. 

 The comparatively imperfect developement of the tusks in 

 the pig, and the consolidation of the toes, are the most 

 striking effects produced in this class of animals. 



" The strongest marks of human influence are seen in 

 the animals of which man has made the most complete 

 conquest ; — In the dog, who Is so perfectly devoted to us, 

 that he seems to have sacrificed to us his individual charac- 

 ter, interest, and feelings. Carried by man all over the 

 world, subjected to the action of the most powerful causes. 



