"In order to face the constant danger of hurt and even of destruction, his predatory and protective faculties were unduly developed. He became quicker of movement than the other dogs, swifter of foot, craftier, deadlier, more lithe, more lean with ironlike muscle and sinew, more enduring, more cruel, more ferocious, and more intelligent. He had to become all these things, else he would not have held his own nor survived the hostile environment in which he found himself."

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