206 • Notes, iii. 6—^. 



8. In saying that in most animals-the heart lies above the lungs,, A. means, I imagine, 

 that -in birds and reptiles the lung extends far down below the site of the heart ; which 

 is in fact the case, if we allow, as A, did, that the air-sacs form "part of the bird's lung. 

 Cf. Note lo. . ■ 



9. Their "heat is great, and therefore they require a large lung to temper it. 



10. A.'s account suits very well to the lungs of amphibians and reptiles, but as regards 

 birds can only be explained by admitting that the true lungs, owing to. their comparatively 

 small size and their being confined to the back of the thorax, had escaped his notice, and* 

 that he took the much larger air-sacs for them, or at any rate included these in the lupg. 

 A. thought that a bladder-like Fung was an inferior organ, because.it had but a small 

 amount of blood. It is an inferior organ, because of the small surface for the exposure 

 of blood to the air. ' . 



11. "Birds with talons may be said, speakirig generally, never to drink at all. Other 

 birds drink, but sparingly" {H. A. viii. i8, 3). As to reptiles, cf. iii. 8, Note 4. 



12. The real reason why a reptile or amphibian can remain under water for a long 

 time is that its tissues produce, for equal weights, less carbonic acid in a given time than 

 those of _other animals, so that there, is less rapid need fof respiration (cf. Bert. Lemons mr 

 la Resp.). As to such birds, as the duck, etc., it is the large amount of blood in 

 their body, which, f9rming a store of oxygen, enables them to remain so long without 

 breathing. 



13. A. always regards birds as cold animals, though their great heat is readily percep- 

 tible to touch, and cannot have been unknown to htm. It is, however, in vital heat, not 

 in ordinary heat, that he Jiolds them deficient. Cf. introd. p. xxxi. 



14. A. seems to have had some strange notion that a fan cools a body not merely by 

 bringing a continuous current of cold air into contact with it, but directly by its own 

 motion, that is independently of the air. " Every hot body," he say's, " is cooled by the 

 motions of bodies external to itself" (D. P. iii. 4, 30). 80 he supposes fiere that 

 when an animal is under water, its lung will continue -in motion, and that, though no air 

 is admitted, yet the motion will itself produce a certain amount of cooling in the neigh- 

 bouring parts. See also De Resp. 9, 6. " • . 



15. Cf. ii. 9, 9. 



16. " Erect " seems to be used here, not in its ordinary sense of standing on the hind 

 legs, but as having the body removed from the ground, so as to apply to "quadrupeds as 

 well as to men. ' . • 



17. Alluding to the viper, • . . 



18. Plato thought that the lung in all animals was bloodless (cf. Joweifs Tr. ii. 564). 

 A. holds that the lung of mammals is the Organ which of all is most richly supplied with 



. blood, but that the lung of ovipara is " bladder-like and contains but little blood." He 

 alludes elsewhere (ZT. A. i. 17, 7) to Plato's erroneous statement, without naming him. 

 ■ (Ch. 7.) 1. It seems to have been the universal opinion of the ancients that the 

 spleen was the left homologue of the liver. In modem times the more general view is 

 that of Miifler, that there is no such relation between them, each being an azygos organ. 

 The ancient opinion is not, however, without its modern advocates. Dr. Doellinger for 

 instance (firundriss der Naturlehre des menschl. Organ. 1805) supported it ; and still 

 more recently Dr. Sylvester {The Discov. of the -Nature of the Spleen, 1870) has argued 

 with much ingenuity that *' the spleen is not a blood-gland in the mesial line of the body, 

 having no homologous relationship with the liver," but that "it is the left lateral homo- 



. logue of a portion of the liver, the letter being a combination of a sanguiferous gland and 

 a biliary apparatus, " and the spleen the homologue of the form'er portion of it. 



