Of salt, man can perceive one part in 640 through his sense of taste; of quinine, one part in 152.000. Likewise, his optic nerve becomes conscious of a change of color when one part in 1,000,000 of methyl violet is added to colorless water. The delicacy of a man's olfactory nerve surpasses that of his optic nerve, as his optic nerve is more sensitive than the nerves of taste. One grain of musk will go on and on for days and weeks and even years permeating a whole room and writing the image of its odor upon the brain of man without apparent diminution.

Yet man's nose is as irresponsive to the scents that stir the trained dog to action as a hippopotamus is irresponsive to a dissertation on the fourth dimension. To what astonishing delicacy, therefore, must a dog's olfactory nerve attain to enable him to detect such infinitesimal emanations!

One cannot too highly extol the work of the hunting dog. As a recent writer says, "We all applaud the stiff antics of the high-school-trained horse and wax enthusiastic over the tricks of the lion-tamer's tawny pupil, but not one in fifty of us steps to reflect that the bird-dog displays an intelligence far beyond these. He ranges over the country as free as the winter wind, but always under perfect control. No bit guides him, yet he turns to the right or the left at the wave of a hand. No snapping whip compels obedience, but he obeys the call of a whistle promptly and cheerfully".