OSSA INNOMINATA. 99 



ligamentous fibres, fastening the ilium to the sacrum; but pos- 

 terior to it is the surface of origin to the multifidus spinae, and 

 the sacro-lumbalis muscles. 



Os Pubis, (Pubis.) This bone constitutes the fore part of 

 the innominatum, and is much the smallest of the three. It is 

 composed by a body and two large branches from it, one run- 

 ning downwards to join the ischium, and the other backwards 

 and upwards to join the ilium. 



The body of the pubes is joined to its fellow on the opposite 

 side by a flat surface, called the symphysis, which is eighteen 

 or twenty lines in its long diameter. The superior part of the 

 body also presents a flat surface, called its horizontal portion, 

 which is bounded outwardly by the spinous process about an 

 inch from the symphysis. The horizontal portion and the sym- 

 physis form a right angle. From the exterior face of the spine 

 two ridges proceed outwardly; the posterior is the crista; it is 

 sharp, elevated, and makes the anterior half of the linea ilio- 

 pectinea; the anterior ridge is lower down, increases in its 

 elevation as it goes along, is rounded, and runs nearly horizon- 

 tally to terminate in the anterior upper margin of the acetabu- 

 lum. Between the two ridges is a superficial triangular con- 

 cavity occupied by the origin of the pectineus muscle; the base 

 of the triangle is bounded by the protuberance formed at the 

 junction of the pubes and ilium, and it is exactly over this 

 part that the femoral vessels pass; its apex is the spine or spi- 

 nous process of the pubes. The extremity of the upper branch 

 of the pubes is triangular, and much enlarged where it contri- 

 butes to the acetabulum. 



The inferior branch of the pubes, technically called its 

 ramus, is a flattened process about an inch in length, and, as 

 mentioned, descends to join the ischium. Its exterior is plain, 

 and has no mark deserving of attention ; but the internal face, 

 near the anterior margin, is concave for attaching the crus of 

 the penis or of the clitoris. 



The body of the pubes in front is concave, and gives origin 

 to the adductor longus and brevis muscles; behind, it is only 

 sufficiently concave to participate in the general concavity of 

 the pelvis. 



