212 SPECIAL ANATOMY OF THE SKELETON 



The anterior portion is subdivided by a prominent vertical ridge, passing from 

 base to apex, into two parts; the outer one gives origin to the Adductor magnus; 

 the inner, to the great sacrosciatic ligament. The upper portion is subdivided 

 into two facets by an oblique ridge which runs downward and outward; from the 

 upper and outer facet arises the Semimembranosus; from the lower and inner, 

 the Biceps and Semitendinosus. 



The ramus or inferior ramus or ascending ramus of the ischium (ramus inferior 

 ossis isckii) is the thin, flattened part of the ischium which ascends from the 

 tuberosity upward and inward, and joins the descending ramus of the os pubis, 

 their point of junction being indicated in the adult by a rough line. The outer 

 surface of the ramus is rough, for the origin of the Obturator externus muscle, 

 and also some fibres of the Adductor magnus; 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 presents two ridges and an intervening 

 space. The ridges are continuous with similar ones on the descending ramus 

 of the os pubis; to the outer one is attached the deep layer of the superficial perineal 

 fascia, and to the inner, the superficial layer of the triangular ligament of the 

 perineum. If these two ridges are traced downward, they will be found to join with 

 each other just behind the point of origin of the Transversus perinei muscle; 

 here the two layers of fascia are continuous behind the posterior border of the 

 muscle. To the intervening space, just in front of the point of junction of the 

 ridges, is attached the Transversus perinaei muscle, and in front of this arises a 

 portion of the crus penis vel clitoridis and the Erector penis vel clitoridis muscle. 

 Its outer border is thin and sharp, and forms part of the inner margin of the 

 obturator foramen. 



The Pubis (os pubis) forms the anterior part of the os innominatum, and, with the 

 bone of the opposite side, forms the front boundary of the true pelvic cavity. It is 

 divisible into a body, a superior or ascending and an inferior or descending ramus. 



The body (corpus ossis pubis) is the broad portion of bone formed by the junction 

 of the two rami. It is somewhat quadrilateral in shape, and presents for examina- 

 tion two surfaces and three borders. The anterior surface is rough, directed 

 downward and outward, and serves for the attachment of various muscles. From 

 the upper and inner angle, immediately below the upper border, arises the Adduc- 

 tor longus; lower down, from without inward, arise the Obturator externus, the 

 Adductor brevis, and the upper part of the Gracilis. The posterior surface, 

 convex from above downward, concave from side to side, is smooth, and forms 

 part of the anterior wall of the pelvis. It gives origin to the Levator ani, Obturator 

 internus, a few muscle fibres prolonged from the bladder, and the puboprostatic 

 ligaments. At the outer part of the upper border is a prominent tubercle, which 

 projects forward and is called the spine (tuberculum pubicum); to it is attached 

 Poupart's ligament. Passing upward and outward from this is a prominent 

 ridge, forming part of the iliopectineal line (linea arcuata). It marks the brim of 

 the true pelvis; to it are attached a portion of the conjoined tendon of the Internal 

 oblique and Transversalis muscles, Gimbernat's ligament, and the triangular 

 fascia of the abdomen. Internal to the spine the upper border is called the crest, 

 which extends from this process to the inner extremity of the bone. It affords 

 attachment to the conjoined tendon of the Internal oblique and Transversalis, 

 and to the Rectus abdominis and Pyramidalis muscles. The point of junction 

 of the crest with the inner border of the bone (symphysis) is called the angle; 

 to it, as well as to the symphysis, is attached the internal pillar of the external 

 abdominal ring. The internal border is articular; 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 a thin layer of cartilage, 

 placed between it and the central fibrocartilage. The outer border presents a 



