THE OS lyyOMIXATUM. 377 



veiling space, just in front of the point of junction of the ridges, is attached the 

 Transversus perinaei muscle, and in front of this 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 Os Pubis forms the anterior part of the os innominatum, and, with the bone 

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

 divisible into a body, a horizontal ramus. and a descending ramus. 



The body is somewhat quadrilateral in shape, and presents for examination two 

 surfaces and four borders. The anterior surface is rough, directed forward, down- 

 ward, and outward. To the upper and inner angle, immediately below the crest, 

 is attached the Adductor longus : lower down, from without inward, are attached 

 the Obturator externus. the Adductor brevis. and the upper part of the Gracilis. 

 The p<:>*t:-rt"i- *uf*\i.<~-> .-. convex from above downward, concave from side to side, is 

 smooth, and forms part of the anterior wall of the pelvis. It gives attachment 

 to the Levator ani. Obturator internus, a few muscular fibres prolonged from the 

 bladder, and the pubo-prostatic ligaments. On the outer end of the upper border, 

 at about its junction with the horizontal ramus, there is a prominent tubercle called 

 the sp!i/>- : to it is attached the outer pillar of the external abdominal ring and 

 Poupart's ligament. Passing outward from the spine is a prominent ridge, pubic 

 portion <,f tlie itto-pcctmeal ///#-. which marks the brim of the true pelvis: to it is 

 attached a portion of the conjoined tendon of the Internal oblique and Transver- 

 sal is muscles. Gimbernat's ligament, and the triangular ligament of the abdomen. 

 Internal to the spine is the upper border or crest, which extends to the inner bor- 

 der of the bone. It affords attachment anteriorly to the conjoined tendon of the 

 Internal oblique and Transversalis, and posteriorly to the Rectus and Pyramidalis 

 muscles. The point of junction of the crest with the inner border of the bone is 

 called the angle : to it. as well as to the symphysis, is attached the internal pillar 

 of the external abdominal ring. The inner border, together with that of the bone 

 of the opposite side, forms 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 a thin layer of cartilage placed 

 between it and the central fibre-cartilage. The outer border is sharp and forms 

 part of the circumference of the obturator foramen. The lower border is united 

 to the descending ramus. 



The horizontal ramus extends from the body to the point of junction of the os 

 pubis with the ilium, and forms the upper part of the circumference of the obturator 

 foramen. It presents for examination a superior, inferior, and posterior surface, and 

 an outer extremity. The *n/ //</ ani-fn ? presents a continuation of the pubic portion 

 of the ilio-pectineal line, already mentioned as commencing at the spine of the bone. 

 In front of this ridge the surface of bone is triangular in form, wider externally than 

 internally, smooth, and affords attachment to the Pectineus muscle. The surface 

 is bounded externally by a rough eminence, the iUo-pectineal, which serves to 

 indicate the point of junction of the ilium and pubes, and gives attachment to 

 the Psoas parvus when this muscle is present. The inferior surface forms the 

 upper boundary of the obturator foramen, and presents externally a broad and 

 deep oblique groove, for the passage of the obturator vessels and nerve; and 

 internally a sharp margin which forms part -f the circumference of the obturator 

 foramen, and to which the obturator membrane is attached. The posterior surface 

 forms part of the anterior boundary of the true pelvis. It is smooth, convex from 

 above downward, and affords attachment to the upper fibres of the obturator 

 internus. The outer extremity, the thickest part of the ramus, forms one-fifth of 

 the cavity of the acetabulum. 



The descending ramus of the os pubis is thin and flattened. It passes outward 

 and downward, becoming narrower as it descends, and joins with the ramus of the 

 ischium. Its <:n~it<-rlr .>irf<ice is rough, for the attachment of muscles the Gracilis 

 along its inner border ; a portion of the Obturator externus where it enters into 

 the formation of the foramen of that name ; and between these two muscles the 



