594 



AVES BIRDS. 



Fig. 268. 



genera, such as the Ostrich, the Emeu, &c. where the wings are 

 not available for flying, the keel is entirely wanting, and the sternum 

 forms merely a kind of osseous shield, covering comparatively a very 

 small portion of the breast. 



(660.) Whoever considers the position of the hip-joint in the fea- 

 thered tribes, and reflects how far it is necessarily removed behind the 

 centre of gravity when the bird walks, carrying its body in a horizon- 

 tal position, will at once 

 perceive that the pelvic 

 portion of the spine, 

 having to sustain the 

 whole weight of the 

 trunk under the most 

 unfavourable circum- 

 stances, and at the same 

 time to give origin to 

 the strong and massive 

 muscles wielding the 

 thigh, must be consoli- 

 dated and strengthened 

 in every possible man- 

 ner; and that even the 

 slight degree of move- 

 ment permitted in the 

 dorsal region would here be inadmissible. The lumbar and the sacral 

 vertebrae, and the entire pelvis, are therefore at an early period 

 solidly united together by anchylosis into one bone, and the num- 

 ber of the vertebrae composing this part of the skeleton is only 

 distinguishable from the situation of the intervertebral foramina 

 through which the spinal nerves are given off. In very young 

 birds the pelvis is evidently formed by the three elements that 

 usually enter into its composition ; and the ilium, the ischium, and 

 ihepubes, as well as the ischiadic notch and obturator foramen, 

 will all be at once recognised by the anatomist, occupying their 

 usual relative positions ; although he will not fail to notice one re- 

 markable circumstance, namely, that except in one instance, the 

 Ostrich, the ossa pubis do not meet in front, so that there is no 

 pubic arch or symphysis. 



(661.) The anterior extremity of a bird, although an instrument 

 of flight, is found, when stripped of those feathers and long quills 

 that form the extensive surface presented by this member during 



