B. IV.] THE HISTORY OF ANIMALS. 97 



places they cackle, in others whistle. Small birds do not utter 

 the same voice as their parents, if they are brought up away 

 from them, and have only heard other singing birds. For the 

 nightingale has been observed instructing her young, so 

 that the voice and speech are not naturally alike, but are 

 capable of formation. And men also have all the same voice, 

 however much they may differ in language. The elephant 

 utters a voice by breathing through its mouth, making no 

 use of its nose, as when a man breathes forth a sigh ; but 

 with its nose it makes a noise like the hoarse sound of a 

 trumpet. 



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 offish that remains any length 

 of time upon the ground ; fishermen frequently draw them 

 out hanging like globes around the bait. The following con- 

 siderations 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 



I 



