THE OTBElfAIi SKELETON, 1 73 



It does this by affording attachment to a bony girdle — called 

 the " pelvis " — from which the lower limbs are suspended. 



The sacrum of a bird, being so extensive, includes more 

 vertebrsB than does the pelvis of any beast or reptile, and we 

 may distinguish three parts in it : — 



(1) A part made up of vertebrae which' may be taken to 

 represent vertebrae of the trunk, which have been absorbed by 

 it. The vertebrae which form this part may be called lumbo- 

 sacral *. 



(2) A part which may be taken to be especially sacral, or the 

 " sacrum " par excellence. Its vertebrae are the true sacral 

 ones. (Fig. 149, 8, 9, & lo.) 



Fig. 149. 



J"- 

 Ventral Aspect of Sacrum of Young Ostrich. 



\-12, Centra ; d-d?, diapophyBes of corresponding rertebrse ; p'^-p^", para- 

 pophyses of corresponding vertebrae ; dp, conjoined dia- and para- 

 pophyses of the vertebra marked 11, 



(3) A part made up of vertebrae which may be taken to 

 represent vertebrae of the tail, which have been absorbed ' into 

 the sacrum. The vertebrae of this region are termed uro-sacral. 



The number of vertebrae thus anchylosed together varies 

 from a dozen or eleven to thirteen, which is about the average, 

 up to twenty. 



The whole sacrum is an elongated structure somewhat spindle- 

 shaped, and is compressed between those bones of the pelvis 



* So called because these vertebras seem to answer to those vertebrae of 

 man and other mammals vphioh are termed " lumbar," and are the vertebrje 

 ■which come between their dorsal vertebrse and their sacrum. 



