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.
The scent is more delicate still in insects. A bee flies directly to the flower that it wants to reach; a worm crawls to its leaf; a bedbug, a flea, a mosquito scents a man a hundred thousand of its steps away.
If the particles which separate from a substance and enter our noses are small, how small must be those particles that reach the organ of smell of the insects!
TOUCH AND SIGHT
Twist the forefinger over the middle finger and touch a small ball with them, so that it may roll between the two fingers, and shut your eyes. You will think that there are two balls. Open your eyes,—and you will see that it is one ball. The fingers have deceived you, but the eyes correct you.
Look (best of all sidewise) at a good, clean mirror,—you will think that it is a window or a door, and that there is something behind it. Touch it with a finger,—and you will see that it is a mirror. The eyes have deceived you, but the fingers correct you.