OS INNOMINATUM. 153 



distinct impressions. Two of these, seen at the front part of the tuberosity, are 

 rough, elongated, and separated from each other by a prominent ridge ; the outer 

 one gives attachment to the Adductor magnus, the inner one to the great sacro- 

 sciatic ligament. Two, situated at the back part, are smooth, larger in size, and 

 separated by an oblique ridge ; from the upper and outer arises the Semi-mem- 

 branosus ; from the lower and inner, the Biceps and Semi-tendinosus. The upper- 

 most part of the tuberosity gives attachment to the Gemellus inferior. 



The ramus is the thin flattened part of the ischium, which ascends from the 

 tuberosity upwards and inwards, and joins the ramus of the pubes, their point of 

 junction being indicated in the adult by a rough eminence. Its outer surface is 

 rough for the attachment of the Obturator externus muscle. Its inner surface 

 forms part of the anterior wall of the pelvis. Its inner border is thick, rough, 

 slightly everted, forms part of the outlet of the pelvis, and serves for the attach- 

 ment of the crus penis. Its outer border is thin and sharp, and forms part of the 

 inner margin of the obturator foramen. 



The Pubes forms the anterior part of the os innominatum ; it is divisible into a 

 horizontal ramus or body, and a perpendicular ramus. 



The body or horizontal ramus presents for examination two extremities, an outer 

 and an inner, and four surfaces. The outer extremity, the thickest part of the bone, 

 forms one-fifth of the cavity of the acetabulum ; it presents, above, a rough emi- 

 nence, the ilio-pectineal, which serves to indicate the point of junction of the 

 ilium and pubes. The inner extremity is the symphysis ; it is oval, covered by 

 eight or nine transverse ridges, or a series of nipple-like processes arranged in 

 rows, separated by grooves ; they serve for the attachment of the interarticular 

 fibro-cartilage, placed between it and the opposite bone. The upper surface, 

 triangular in form, wider externally than internally, is bounded behind by a sharp 

 ridge, the pectineal line, or linea ilio-pectinea, which, running outwards, marks the 

 brirn of the true pelvis. The surface of bone in front of the pubic portion of the 

 linea iliq-pectinea serves for the attachment of the Pectineus muscle. This ridge 

 terminates internally at a tubercle, which projects forwards, and is called the spine 

 of the pubes. The portion of bone included between the spine and inner extre- 

 mity of the pubes is called the crest ; it serves for the attachment of the Rectus, 

 Pyramidalis, and conjoined tendon of the Internal oblique and Transversalis. 

 The point of junction of the crest with the symphysis is called the angle of the pubes. 

 The inferior surface presents, externally, a broad arid deep oblique groove, for 

 the passage of the obturator vessels and nerve ; and, internally, a sharp margin, 

 which forms part of the circumference of the obturator foramen. Its external 

 surface, flat and compressed, serves for the attachment of muscles. Its internal 

 surface, convex from above downwards, concave from side to side, is smooth and 

 forms part of the anterior wall of the pelvis. 



The descending ramus of the pubes passes outwards and downwards, becoming 

 thinner and narrower as it descends, and joins with the ramus of the ischium. Its 

 external surface is rough, for the attachment of muscles. Its inner surface is 

 smooth. Its -inner border is thick, rough, and everted, especially in females. In 

 the male, it serves for the attachment of the crus penis. Its outer border forms 

 part of the circumference of the obturator foramen. 



The cotyloid cavity, or acetabulum, is a deep, cup-shaped, hemispherical depres- 

 sion, formed, internally, by the pubes; above, by the ilium; behind and below, 

 by the ischium ; 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 prominent uneven rim, which is thick and strong above, and serves 

 for the attachment of a fibre-cartilaginous structure, which contracts its orifice, 

 and deepens the surface for articulation. It presents on its inner side a deep 

 notch, the cotyloid notch, which transmits the nutrient vessels into the interior of 

 the joint, and is continuous with a circular depression at the bottom of the cavity; 

 this depression is perforated by numerous apertures, lodges a mass of fat, and its 

 margins serve for the attachment of the ligamentum teres. The notch is con- 



