Chapter X.

1. Concerning the sleep and wakefulness of animals. It is quite manifest that all viviparous animals with feet both sleep and are awake; for all that have eyelids sleep with the eyes closed; and not only men appear to dream, but horses, oxen, sheep, goats, dogs, and all viviparous quadrupeds. Dogs show this by barking in their sleep. It is not clear whether oviparous animals dream, but it is quite plain that they sleep.

2. And so it is in aquatic animals, as fish, the malacia, the malacostraca, the carabi, and such like creatures. The sleep of all these animals is short: it is plain that they do sleep, though we can form no conclusion from their eyes, for they have no eyelids, but from their not being alarmed; for if fish are not tormented with lice, and what are called psylli, they may be captured without alarming them, so that they can be even taken with the hand. And if fish remain at rest during the night a great multitude of these creatures fall upon and devour them.

3. They are found in such numbers at the bottom of the sea as to devour any bait made of fish that remains any length of time upon the ground; fishermen frequently draw them out hanging like globes around the bait. The following considerations will serve still more to confirm our suppositions that fishes sleep; for it is often possible to fall upon the fish so stealthily as to take by the hand, or even strike them during this time; they are quite quiet, and exhibit no signs of motion except with their tails, which they move gently. It is evident, also, that they sleep, from their starting if anything moves while they are asleep, for they start as if they were waked out of sleep.

4. They are also taken by torchlight while asleep; those who are seeking for thynni surround them while asleep; it is evident that they can be captured from their stillness, and the half-open white (of their eyes). They sleep more by night than by day, so that they do not move when they are struck; they generally sleep holding by the ground, or the sand, or a stone, at the bottom, concealing themselves beneath a rock, or a portion of the shore. The flat fishes sleep in the sand; they are recognized by their form in the sand, and are taken by striking them with a spear with three points. The labrax, chrysophrys, cestreus, and such-like fish are often taken with the same kind of weapon while asleep in the day time, but if not taken then, none of them can be captured with such a spear.

5. The selache sleep so soundly that they may be taken with the hand; the dolphin, whale, and all that have a blow-hole, sleep with this organ above the surface of the sea, so that they can breathe, while gently moving their fins, and some persons have even heard the dolphin snore. The malacia sleep in the same manner as fish, and so do the malacostraca. It is evident from the following considerations that insects sleep; for they evidently remain at rest without motion; this is particularly plain in bees, for they remain quiet, and cease to hum during the night. This is also evident from those insects with which we are most familiar, for they not only remain quiet during the night because they cannot see distinctly, for all creatures with hard eyes have indistinct vision, but they seem no less quiet when the light of a lamp is set before them.

6. Man sleeps the most of all animals. Infants and young children do not dream at all, but dreaming begins in most at about four or five years old. There have been men and women who have never dreamt at all; sometimes such persons, when they have advanced in age, begin to dream; this has preceded a change in their body, either for death or infirmity. This, then, is the manner of sensation, sleep and wakefulness.