v 





116 os PUBIS. 



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 lower circumference of the obturator foramen. The 

 ramus of the ischium is continuous with the ramus of the pubis, and is 



slightly everted 



fTii r\ Tk 



The Os PUBIS is divided into a horizontal portion or body (horizonta 

 ramus of Albinus), and a descending portion or ramus ; it presents fo 

 examination an external and internal surface, a superior and inferior bor 

 der, and symphysis. 



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

 minent at its outer extremity, where it forms part of the acetabulum. 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 pecti- 

 neal 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 promi- 

 nence, the ilio-pectineal eminence, w r hich divides the surface for the femoral 

 vessels, from another depression which overhangs the acetabulum, and 

 lodges the psoas and iliacus muscles. The ilio-pectineal eminence more- 

 over marks the junction of the pubes with the ilium. The inferior bordei 

 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 bound- 

 ary of the obturator foramen. The symphysis is the inner extremity of 

 the body of the bone ; it is oval and rough, for the attachment of a liga- 

 mentous structure analogous to the intervertebral substance. 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 con- 

 siderably everted, to afford attachment to the crus penis. 



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

 ated at the point of union between the ilium, ischium, and pubes ; a little 

 less than two-fifths being formed by the ilium, a little more than two-fifths 

 by the ischium, and the remaining fifth by the pubes. It is bounded by 

 a deep rim or lip, w r hich is broad and strong above, where most resistance 

 is required, and marked in front by a deep notch, which is arched over 

 in the fresh subject by a strong ligament, and transmits the nutrient ves- 

 sels into the joint. At the bottom of the cup and communicating with the 

 notch, is a deep and circular pit (fundus acetabuli) which lodges a mass 

 of fat, and gives attachment to the broad extremity of the ligamentum teres. 



The obturator or thyroid foramen is a large oval interval between the 

 ischium and pubes, bounded by a narrow rough margin, to which a liga- 

 mentous membrane is attached. The upper part of the foramen is increased 

 in depth by the groove in the under surface of the os pubis which lodges 

 the obturator vessels and nerve. 



Development. By eight centres ; three principal, one for the ilium, one 

 tor the ischium, and one for the pubes ; and five secondary, one, the 

 Y-shaped piece for the interval between the primitive pieces in the aceta- 

 bulum, one for the crest of the ilium, one (not constant) for the anterior 

 and inferior spinous process of the ilium, one for the tuberosity of the 

 .schiura, and one (not constant) for the angle of the os pubis. Ossification 



