ANATOMY. 9 
facet for articulation with the sacrum. The anterior 
border or crest is concave; the external has a medullary 
foramen and vascular grooves; the internal forms the 
great sciatic notch. The external angle or point of 
the hip has four tuberosities for muscular attachment. 
The internal, or antero-internal angle is a rough 
tuberosity curving upwards and backwards, forming, 
with the corresponding portion of the opposite ilium, 
the summit of the croup. The posterior or cotyloid 
angle offers a facet for the cotyloid cavity, the supra- 
cotyloid crest, the ilio-pectineal eminence, and some 
muscular imprints. 
The zschtum is the most posterior of the three 
bones. It is flat and irregularly quadrilateral in shape, 
and is composed of a solid portion (the body) anda 
narrow part (the neck). It is divided into two faces, 
four borders, and four angles. The upper face is 
smooth, and forms the floor of the pelvic cavity; the 
inferior face is roughened for the attachment of 
muscles, and presents the ischial crest. The anterior 
border forms the obturator foramen, the external the 
small sciatic notch; the posterior forms the ischial 
arch, while the internal is articular. The antero- 
external or cotyloid angle presents a diarthrodial facet, 
and the posterior extremity of the supra-cotyloid crest ; 
the antero-internal angle is articulated with the pubis ; 
the postero-external forms the ischial tuberosity ; and 
the postero-internal articulates with that of the 
opposite side. 
The pubis is the smallest of the three bones, and is 
situated between the ilium and ischium. It is divided 
