In this sense he may be said to have made for himself useful breeds.
The great power of this principle of selection is not hypothetical.
It is certain that several of our eminent breeders have, even within a single lifetime, modified to a large extent their breeds of cattle and sheep.
In order fully to realise what they have done it is almost necessary to read several of the many treatises devoted to this subject, and to inspect the animals.
Breeders habitually speak of an animal's organisation as something plastic, which they can model almost as they please.