OSTEOLOGY. 85 



its whole length to a reflection inwards of the sacro-sciatic 

 ligament, which covers the origin of obturator internus 

 from the superior part of the margins of the foramen of 

 the same name, separating it from the pelvic viscera. The 

 posterior 2)rocess of the ischium is triangular and tuberous - 

 at its extremity, which extends outwards and backwards,, 

 and is termed the tuberosity of the ischium. It presents 

 a .small rough ridge, extending forwards along its outer ■ 

 margin to the neck, from which ischio-femoralis arises. - 

 To the posterior tuberous part triceps abductor femoris, 

 biceps rotator tibialis, ischio tibialis and erector penis are 

 attached. The inner margin of this process slopes inwards 

 towards its fellow, which it joins at an oblique angle at the 

 symphysis. This is the ischial arch, and round it the urethra 

 passes from the pelvis into the penis. In so doing it is bound ■ 

 down by a small ligament and by the crura, which, being 

 attached on either side,converge to form corpus cavernosum. 



OS PUBIS consists of three sides and three angles ; its 

 inner margin lies in contact with its fellow, and thus forms 

 symphysis pubis, continuous with and analogous to sym- 

 physis ischii. The posterior angle is united to the antero- 

 internal process of the ischium, and from it the outer 

 margin forms an arch running forwards and outwards^ 

 which, after completing the obturator foramen, terminates 

 in the junction with os ischium and os ilium, forming the 

 acetabulum. The anterior margin, forming the brim of the 

 floor of the pelvis, is at first smooth, centrally presents a 

 rough prominence, pectineal! tubercle, to which pectineus 

 is attached, and inwardly these two pectinean tubercles are 

 connected by a dense fibrous band, which affords attach- 

 ment to the abdominal muscles anteriorly, and posteriorly 

 is partly continuous with the connecting ligament of the 

 symphysis, while the rest of it passes through a groove, 

 which occupies the under surface of os pubis, extending 

 outwards to the pubic notch of the acetabulum. Sym- 

 physis pubis superiorly forms a smooth concave surface for 

 the bladder to rest upon, and externally to this the inward 

 reflection of the sacro-sciatic ligament is attached. To the' 

 under surface of the whole symphysis the common tendon 

 of the graciles is attached centrally, and on either side a 

 biceps adductor femoris. 



The FEMUR is a long, round bone, extending from the 

 hip to the stifle. It is the largest bone in the body, and 



