Notes, iv. 12. 245 



comparison ; the main stem of the toe answering to the ridge of the nose, the lobes on 

 either side to the flattened nostrils. 



9. The scapula in birds is a simple elongated bone, not flattened out into a plate or 

 blade, and so was not recognised by A. as a " blade-bone," just as he did not recognise 

 the astragalus unless it had the form suiting it for use as a " hucklebone." Cf. iv. 10, 

 Note 44. 



10. A. uses two sets of terms to describe the bandings of the limbs (i) Forwards and 

 backwards, {2) Inwards and outwards. A limb is said to be bent fonvards or backwards, 

 when its convexity is turned forwards or backwards ; e.g. the leg of a man is bent 

 forwards ; so is the fore-leg of a horse. But the hind-leg of a horse is bent backwards ; 

 the arm of a man is bent backwards with a slight inclination to the side. A limb is 

 bent inwards, when its concavity is turned in the direction in which the main bulk of 

 the body lies ; outwards when the concavity is turned away from this. Thus both the 

 fore and the hind legs of a horse are bent inwards. So also the leg of a bird is bent 

 inwards ; but the leg of a man is bent outwards. 



It must be remembered that A. knows nothing of the homologies of the various joints. 

 He simply takes the limbs as wholes, and compares the general direction of their main ^ 

 curvature in different animals. 



11. A. rightly says that no sanguineous animal has more than four organs of 

 locomotion, that is, more than four limbs. There are passages from which it might be 

 inferred that he imagined, less correctly, that they never have less than four (cf. iv. 13. 

 Note 6). But in the De Incessu (10, l) he expressly repudiates such a statement. 



12. That is not, as whales and fishes, in the water ; nor, as birds, in the air. 



13. A. had clearly neither dissected, nor seen the skeleton of, an ostrich. In all other 

 birds known to him the sternum is provided with a keel, which he compares ^De Incessu, 

 10, 9) to the sharp prow of a felucca, reminding one of the term " Carinatae " now given 

 to birds with a keeled sternum. 



14. The mass of muscles that move the wings is of course meant. It must be 

 remembered that A. knew nothing of muscular contraction (cf. iii. 4, Note 20). 



15. It might be supposed from this passage that A. imagined a bird to be developed 

 without an allantois and merely with an umbilical vesicle. But from other passages 

 (Z?. G. iii. 3, 4 ; D. G. iii. 2, 22 — 28 ; H. A. vi. 3, 8) it is plain that this was not the 

 case. He describes the foetal bird and reptile as differing from fishes in having two 

 umbilical appendages, one going to the membrane surrounding the yelk, and serving to 

 introduce the nutriment thence derived, the other (allantois) to the membranous expansion 

 which lines the inner surface of the shell. This latter appendage, he says, collapses as 

 the embryonic bird enlarges ; while the former with the yelk is drawn back into the 

 abdominal cavity, the walls of which unite together behind it. He had not observed 

 the umbilical vesicle of mammals, which is comparatively small, and shrivels up at an 

 early period of foetal life, and erroneously supposed their allantois to correspond to the 

 umbilical vesicle of birds and reptiles. This error was not corrected till 1667, when 

 Needhara discovered the umbilical vesicle of mammals, and recognized its correspondence 

 to that of birds. Neither had A. observed that Amphibia in this matter resemble fishes 

 and not reptiles, with which latter he grouped them. 



16. Cf. ii. 9, Note 9. 



17. Birds of prey are awkward movers on the ground or other flat surface, because of 

 their talons, and help themselves along by flapping their wings. But the statement made 

 here and elsewhere {H. A. ix, 32, 12) that they very seldom or never settle on rocks is 

 erroneous ; they often do so, and indeed rocks are the usual resting-place of many. 



