He selected his animals, therefore, with wisdom so that they might afford a differing test, each in its own way, and that one should not merely communicate its own excitement to the other.  He took a dog and a cat.

The cat he chose, now full grown, had lived with him since kittenhood, a kittenhood of perplexing sweetness and audacious mischief.  Wayward it was and fanciful, ever playing its own mysterious games in the corners of the room, jumping at invisible nothings, leaping sideways into the air and falling with tiny moccasined feet on to another part of the carpet, yet with an air of dignified earnestness which showed that the performance was necessary to its own well-being, and not done merely to impress a stupid human audience.  In the middle of elaborate washing it would look up, startled, as though to stare at the approach of some Invisible, cocking its little head sideways and putting out a velvet pad to inspect cautiously.  Then it would get absent-minded, and stare with equal intentness in another direction (just to confuse the onlookers), and suddenly go on furiously washing its body again, but in quite a new place.  Except for a white patch on its breast it was coal black.  And its name was—­Smoke.

“Smoke” described its temperament as well as its appearance.  Its movements, its individuality, its posing as a little furry mass of concealed mysteries, its elfin-like elusiveness, all combined to justify its name; and a subtle painter might have pictured it as a wisp of floating smoke, the fire below betraying itself at two points only—­the glowing eyes.

All its forces ran to intelligence—­secret intelligence, the wordless incalculable intuition of the Cat.  It was, indeed, the cat for the business in hand.

The selection of the dog was not so simple, for the doctor owned many; but after much deliberation he chose a collie, called Flame from his yellow coat.  True, it was a trifle old, and stiff in the joints, and even beginning to grow deaf, but, on the other hand, it was a very particular friend of Smoke’s, and had fathered it from kittenhood upwards so that a subtle understanding existed between them.  It was this that turned the balance in its favour, this and its courage.  Moreover, though good-tempered, it was a terrible fighter, and its anger when provoked by a righteous cause was a fury of fire, and irresistible.

It had come to him quite young, straight from the shepherd, with the air of the hills yet in its nostrils, and was then little more than skin and bones and teeth.  For a collie it was sturdily built, its nose blunter than most, its yellow hair stiff rather than silky, and it had full eyes, unlike the slit eyes of its breed.  Only its master could touch it, for it ignored strangers, and despised their partings—­when any dared to pat it.  There was something patriarchal about the old beast.  He was in earnest, and went through life with tremendous energy and big things in view, as though he had the reputation of his whole race to uphold.  And to watch him fighting against odds was to understand why he was terrible.