xvil] GENERAL CHARACTERS. 2§5 



osseous pieces always coalesce into a single bone, called the 

 os innominatum. 



This is further completed by the addition of epiphyses ; 

 one for the upper extremity of the ilium (corresponding to 

 the supra-scapular epiphysis of the shoulder), others for the 

 most prominent parts of the lower or free borders of the 

 pubis and ischium (symphysis pubis and tuber ischii), and 

 also certain epiphysial ossifications developed in the car- 

 tilage, at the place of junction of the three main elements. 



There is never any secondary osseous bar in the pelvic 

 girdle corresponding to the clavicle of the upper extremity. 



The ilium of Mammals is essentially an elongated, three- 

 sided, or prismatic bone, though the relative size and posi- 

 tion of the various surfaces and angles may differ greatly 

 in different species. In the most characteristic form, one 

 of the surfaces is internal, or directed towards the ver- 

 tebral column, articulating by a flat irregular surface with the 

 lateral " pleuropophysial " ossifications of the sacral verte- 

 bras. This may be called the sacral sicrj ace (see Figs. 106 and 

 107, p. 287, and Fig. 108, ss, p. 295.) Another is directed 

 mainly forwards, and may be called anterior or iliac (is), as 

 it gives origin to the iliacus muscle. The third is posterior 

 or gluteal (gs), as it gives origin to the gluteal muscles. 



Of the borders one is external or acetabular (ab), as it 

 ends below at the margin of the acetabulum ; another is 

 antero-internal or pubic (pb), and the third is postero-internal 

 or ischial (ib), so called because they end below by joining 

 the pubis and the- ischium respectively. 



The innominate bone is always placed more or less 

 obliquely to the vertebral column, the upper or iliac end 

 inclining forwards, and the lower or ischio-pubic end turning 

 backwards, contrary to the usual direction of the scapular arch. 

 In order to give still greater stability and fixity to the pelvic 



in o] 



