When horses are injured, are they improved or deteriorated?

The latter.

Deteriorated, that is to say, in the good qualities of horses, not of dogs?

Yes, of horses.

And dogs are deteriorated in the good qualities of dogs, and not of horses?

Of course.

And will not men who are injured be deteriorated in that which is the proper virtue of man?

Certainly.

And that human virtue is justice?

To be sure.