in-and-in

They were also closely bred in-and-in, seldom or never departing from a particular flock to procure a fresh cross.

Many, perhaps, will see an additional cause in teleological considerations, aiming at the avoidance of in-and-in breeding.

The system of breeding in-and-in proves, in fact, as destructive to flocks, as marriages of near relations to the human kind.

I never knew a more in-and-in-bred seaman, who, when one resource failed, invariably set about the next best visible expedient.

In the latter case breeding in-and-in is usually found to result in decided and rapid deterioration.