CHAPTER VII. 



VARIATION. 



OUR domestic animals, in common with other spe- 

 cies, are endowed with a flexibility or plasticity of the 

 organization that enables them to adapt themselves to 

 the conditions in which they are placed. As a result 

 of a favorable change in the conditions to which ani- 

 mals are subjected, important modifications of the 

 system are obtained, that we recognize as improve- 

 ments in form and quality; while deterioration and 

 loss of valuable characters follow when the prevailing 

 conditions of life are unfavorable to the full and 

 healthy development of the organization. 



From the fact that variations are more readily pro- 

 duced in domesticated varieties than in wild species, 

 it would appear that the change of conditions involved 

 in the process of domestication has not only produced 

 a wide range of variations in the characteristics of 

 animals, but developed an increased plasticity of the 

 organization that renders them more susceptible to the 

 influence of modifying causes. . 



The distinguishing characteristics of the various 

 breeds of animals have been produced, in the main, 

 by the modifying influences that prevail in the locali- 

 ties in which they have originated. 



