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THE INNOMINATE BONE. 211 
origin for the quadratus femoris muscle; in front and below, the adductor magnus 
muscle is attached to it. 
The inner surface of the body and superior ramus of the ischium form in part 
the wall of the true pelvis. Smooth and slightly concave from before backwards, 
and nearly plane from above downwards, it is widest opposite the level of the ischial 
spine. Below this its posterior edge is rounded and forms a groove leading to the 
small sciatic notch, along and over which the tendon of the obturator internus 
passes. To part of this surface the fibres of the obturator internus are attached, 
whilst the inner aspect of the spine supplies points of origin for the coccygeus and 
levator ani muscles, as well as furnishing an attachment to the “ white line” of the 
pelvic fascia. The inner surface of the inferior ramus of the ischium is smooth, 
and so rounded that its inferior edge tends to be everted. To this, as well as to its 
margin, is attached the crus penis, together with the ischio-cavernosus, obturator 
internus, transversus perinei, and compressor urethre muscles. In the female, 
structures in correspondence with these are also found. 
The fore-part of the innominate bone is formed by the pubis; it is by means of 
the union of this bone with its fellow of the opposite side that the pelvic girdle is 
completed in front. 
The pubis (os pubis) consists of two rami—a superior, ascending, or horizontal 
(ramus superior oss. pubis) and an inferior or descending (ramus inferior oss. pubis). 
The broad part of the bone formed by the fusion of these two rami is the body. 
The body is sometimes described as that part of the bone which enters into the 
formation of the acetabulum, but the English nomenclature has here been followed. 
The body of the pubis has two surfaces. Of these the inner or posterior is 
smooth, and forms the fore-part of the wall of the true pelvis; hereto are attached 
the levator ani muscle and puboprostatic hgaments. The anterior or external 
surface is rougher, and furnishes origins for the gracilis, adductor longus, adductor 
brevis, and some of the fibres of the ‘obturator externus muscles. The. inner border 
is provided with an elongated oval cartilage-covered surface by means of 
which it is united to its fellow of the opposite side, the joint being called 
the symphysis pubis. The wpper border, thick and rounded, projects somewhat, so 
as to overhang the anterior surface. It is called the crest. Internally this forms 
with the inner border or symphysis the angle, whilst externally it terminates in a 
pointed process, the spine (tuberculum pubicum). From the crest arise the rectus 
abdominis and pyramidalis muscles, and to the spine is attached the inner end of 
Poupart’s ligament. Passing upwards and outwards from the outer side of the 
body towards the acetabulum, of which it forms about the anterior fifth, is the 
superior ramus (ramus superior). This has three surfaces: an antero-superior, an 
antero-inferior, and an internal or posterior. The antero-swperior surface is 
triangular in form. Its apex corresponds to the pubic spine; its anterior inferior 
border to the obturator crest (crista obturatoria), leading from the spine to the 
upper border of the cotyloid notch; whilst its sharp postero-superior border trends 
upwards and outwards from the spine, and is continuous with the iliac portion of 
the iho-pectineal line just internal to the ilio-pectineal eminence, forming as it 
passes along the superior ramus the pubic portion of that same line (pecten oss. 
pubis). On this line, just within the ilio-pectineal eminence, there is often a short 
sharp crest which marks the insertion of the psoas parvus. The base of the 
triangle corresponds to the ilio-pectineal eminence above, and the upper margin of 
the cotyloid notch below. Slghtly hollow from side to side, and convex from 
before backwards, this surface provides an origin for, and is in part overlain by, the 
pectineus muscle. The internal or posterior surface of the superior ramus is smooth, 
concave from side to side, and slightly rounded from above downwards; by its 
sharp inferior curved border it completes the thyroid foramen, as seen from behind. 
The antero-inferior surface forms the roof of the broad obturator groove (sulcus 
obturatorius) which passes obliquely downwards and forwards between the lower 
margin of the antero-superior surface in front and the inferior sharp border of the 
internal surface behind. The inferior or descending ramus of the pubis (ramus 
inferior) passes downwards and outwards from the lower part of the body. 
