OS PUBIS. 91 



notch of large size, the great sacro-ischiatic, and below the spine the 

 lesser sacro-ischiatic notch ; the former being converted into a foramen 

 by the lesser sacro-ischiatic ligament, gives passage to the pyriformis 

 muscle, the gluteal vessels and nerve, pudic vessels and nerve, and 

 ischiatic vessels and nerves ; and the lesser, completed by the great 

 sacro-ischiatic ligament, to the obturator internus muscle, and to the 

 internal pudic vessels and nerve. The inferior border is thick and 

 broad, and is called the tuberosity. The surface of the tuberosity is 

 divided into three facets ; one anterior, which is rough for the origin 

 of the semi-membranosus ; and two posterior, which are smooth, and 

 separated by a slight ridge for the semi-tendinosus and biceps muscle. 

 The inner margin of the tuberosity is bounded by a sharp ridge, 

 which gives attachment to a prolongation of the great sacro-is- 

 chiatic ligament, and the outer margin by a prominent ridge, from 

 which the quadratus femoris muscle arises. The superior border of 

 the ischium is thin, and forms the lo,wer circumference of the obtura- 

 tor foramen. The ramus of the ischium is continuous with the ramus 

 of the pubis, and is slightly everted. 



The os PUBIS is divided into a horizontal portion or body (hori- 

 zontal ramus of Albinus), and a descending portion or ramus ; it pre- 

 sents for examination an external and internal surface, a superior and 

 inferior border, and symphysis. 



The external surface is rough, for the attachment of muscles ; and 

 prominent at its outer extremity, where it forms part of the acetabu- 

 lum. The internal surface is smooth, and enters into the formation 

 of the cavity of the pelvis. The superior border is marked by a 

 rough ridge, the crest ; the inner termination of the crest is the angle ; 

 and the outer end, the spine or tubercle. Running outwards from the 

 spine is a sharp ridge, the pectineal line, or linea ilio-pectinea, which 

 marks the brim of the true pelvis. In front of the pectineal line is 

 a smooth depression, which supports the femoral artery and vein, and 

 a little more externally an elevated prominence, the ilio-pectineal 

 eminence, which divides the surface for the femoral vessels, from an- 

 other depression which overhangs the acetabulum, and lodges the 

 psoas and iliacus muscles. The ilio-pectineal eminence moreover 

 marks the junction of the pubes with the ilium. The inferior border 

 is broad and deeply grooved, for the passage of the obturator vessels 

 and nerve ; and sharp upon the side of the ramus, to form part of the 

 boundary of the obturator foramen. The symphysis is the inner ex- 

 tremity of the body of the bone ; it is oval and rough, for the attach- 

 ment of a ligamentous structure analogous to the intervertebral sub- 

 stance. The ramus of the pubes descends obliquely outwards, and is 

 continuous with the ramus of the ischium. The inner border of the 

 ramus forms with the corresponding bone the arch of the pubes, and 

 at its inferior part is considerably everted, to afford attachment to the 

 crus penis. 



The acetabulum (cavitas cotyloidea) is a deep cup-shaped cavity, 

 situated at the point of union between the ilium, ischium, and pubes ; 



