first discharged through them and then the food passes in through

the mouth; they have no windpipe and hence can take no harm from

liquid lodging in this organ, only from its entering the stomach.

For these reasons the expulsion of water and the seizing of their food

is rapid, and their teeth are sharp and in almost all cases arranged

in a saw-like fashion, for they are debarred from chewing their food.



18



Among water-animals the cetaceans may give rise to some

perplexity, though they too can be rationally explained.

Examples of such animals are dolphins and whales, and all others

that have a blowhole. They have no feet, yet possess a lung though

admitting the sea-water. The reason for possessing a lung is that

which we have now stated [refrigeration]; the admission of water is

not for the purpose of refrigeration. That is effected by respiration,

for they have a lung. Hence they sleep with their head out of the

water, and dolphins, at any rate, snore. Further, if they are

entangled in nets they soon die of suffocation owing to lack of

respiration, and hence they can be seen to come to the surface owing

to the necessity of breathing. But, since they have to feed in the

water, they must admit it, and it is in order to discharge this that

they all have a blow-hole; after admitting the water they expel it

through the blow-hole as the fishes do through the gills. The position

of the blow-hole is an indication of this, for it leads to none of the

organs which are charged with blood; but it lies before the brain

and thence discharges water.

It is for the very same reason that molluscs and crustaceans admit

water-I mean such animals as Carabi and Carcini. For none of these

is refrigeration a necessity, for in every case they have little

heat and are bloodless, and hence are sufficiently cooled by the

surrounding water. But in feeding they admit water, and hence must