94 TEE BONES. 



Angles. The external, also named the cotyloid angle, is the thickest of the 



three. To it chiefly belongs the rugged depressed surface that constitutes 

 the bottom of the cotyloid cavity. The internal unites with the analogous 

 angle of the opposite pubis. The posterior is consolidated at an early period 

 with the antero-internal angle of the ischium, to inclose, inwardly, the oval 

 foramen. 



ISCHIUM. This is the mean, in volume, of the three pieces of the coxa. 

 Situated behind the pubis and ilium, it is flattened above and below, and of 

 a quadrilateral form. It offers for study : two faces, four borders, and four 

 angles. 



Faces. The superior is smooth and nearly plane, and forms part of the 

 floor of the pelvic cavity. It has a small nutritious foramen directed out- 

 wards. The inferior presents some rugosities clustered particularly about 



the symphysis. 



Fig. 60. 



PELVIS; LATERAL VIEW. 



1, Crest of the ilium ; 2, Angle of the croup ; 3, Shaft of the ilium ; 4, Cotyloid 

 cavity, or acetabulum ; 6, Ischial spine. 



Borders. The anterior, thick and concave, circumscribes the oval foramen 

 posteriorly. The posterior, straight and directed obliquely forwards and 

 inwards, forms, with the analogous border of the opposite bone, a large 

 notch named the iscniatic arch. It exhibits, throughout its extent, a rugged 

 depressed lip (the spine), arising from the side of the inferior face. The ex- 

 ternal, thick and concave, constitutes the lesser ischiatic notch. The internal 

 is joined to the ischium of the other side to constitute a portion of the pelvic 

 symphysis. 



Angles. The antero-external or cotyloidean is the most voluminous of the 

 four, and affords for study : 1, An excavated diarthrodial facet, making part 

 of the cotyloid cavity ; 2, The posterior extremity of the super-cotyloidean 

 crest, limited by a small transverse fissure which separates it from the 

 external border of the bone. The antero-internal angle is consolidated with 

 the posterior angle of the pubis. The poster o- external angle forms the 

 ischiatic tuberosity. This is a large prismatic process which looks upwards, 

 and is prolonged by a salient ridge, elongated from before to behind, with 

 its sharp border turned outwards and downwards. The postero-internal angle 



