When a horse is afraid of anything, it snorts—it clears its nose so as to scent better, and does not stop being afraid until it has smelled the object well.
A dog frequently follows its master’s track, but when it sees him, it does not recognize him and begins to bark, until it smells him and finds out that that which has looked so terrible is its master.
Oxen see other oxen stricken down, and hear them roar in the slaughterhouse, but still do not understand what is going on. But an ox or a cow need only find a spot where there is ox blood, and smell it, and it will understand and will roar and strike with its feet, and cannot be driven off the spot.
An old man’s wife had fallen ill; he went himself to milk the cow. The cow snorted—she discovered that it was not her mistress, and would not give him any milk. The mistress told her husband to put on her fur coat and kerchief—and the cow gave milk; but the old man threw open the coat, and the cow scented him, and stopped giving milk.
When hounds follow an animal’s trail, they never run on the track itself, but to one side, about twenty paces from it. When an inexperienced hunter wants to show the dog the scent, and sticks its nose on the track, it will always jump to one side. The track itself smells so strong to the dog that it cannot make out on the track whether the animal has run ahead or backward. It runs to one side, and then only discovers in what direction the scent grows stronger, and so follows the animal. The dog does precisely what we do when somebody speaks very loud in our ears; we step a distance away, and only then do we make out what is being said. Or, if anything we are looking at is too close, we step back and only then make it out.
Dogs recognize each other and make signs to each other by means of their scent.