PARTS OF ANIMALS, III. vi. 



animals have a large lung, which contains blood ; 

 others a small one and spongy. In the Vivipara it is 

 large and has much blood in it because these creatures 

 have a hot nature : in the Ovipara it is dry and small, 

 but it can expand to a great size when inflated : 

 examples of these are : among land -animals, the 

 oviparous quadrupeds like the lizards, tortoises, and 

 all such creatures, and in addition to these the 

 tribe of winged things, the birds. All these have a 

 spongy lung, which, like froth, runs together and 

 contracts from a large volume into a small one. So 

 it counts as small ; and also it is membranous. As a 

 result, all these creatures are not much subject to 

 thirst, and di'ink but little ; and also they can bear to 

 remain a long time under the water : this is because 

 their heat is scanty and can therefore be sufficiently 

 cooled over a long period by the mere motion of the 

 lung, which is void and air-like. 



(Consequently, one may add, in general these 

 creatures are smaller in size than the majority of 

 animals, as gro\\i:h is promoted by heat, and a plenti- 

 ful supply of blood is a sign that heat is present. 

 Furthermore, heat tends to make the body upright," 

 which explains Λvhy man is the most upright among 

 the animals and the Vivipara the most upright among 

 the quadrupeds. And there are no viviparous 

 creatures, either with or without feet, so fond of 

 creeping into holes as the 0\'ipara are.) 



The lung, then, is present for the sake of the 

 breathing : this is its function ahvays. Sometimes, 

 to serve the purpose of a particular group, it is blood- 

 less, and such as has been described above. There 

 is no common name which is applied to all animals 

 that have lungs. But there ought to be : because 



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