I2O 



Anatomy of Skeleton 



lower are the crest of the Ilium and the Ischio-pubic ramus respectively ; the anterior 

 margin is on the whole a concave line, allowing exit for muscles, etc., below Poupart's 

 ligament, and presents, from above downwards, anterior superior spine, notch, anterior 

 inferior spine, notch, Ilio-pectineal eminence, upper surface of superior ramus of 

 pubis : posterior margin is more irregular and shows posterior superior spine, notch, 

 posterior inferior spine, great sciatic notch, Ischial spine, lesser sciatic notch and 

 tuberosity of Ischium. 



Looked at from the inner side (Fig. 98) the same parts can be recognised in the 

 margins, but three distinct main surfaces are apparent. The first of these is in the 

 upper and back part and looks directly inward : it has an articular area shaped like 

 an ear and hence termed the auricular surface : above and behind this a rough liga- 

 mentous area for the strong posterior sacro-iliac ligaments, and above and behind this 

 again is a muscular area, which really occupies the expanded posterior part of the crest, 

 for the Erector spinaa muscle. A strong bony buttress runs obliquely downwards 

 and forwards from the auricular region to the pubis, called the Ilio-pectineal line, 

 and forming the bony brim of the true pelvis in this region : this divides the bone into 



the remaining two surfaces, an upper one, 

 which is abdominal and formed by the venter 

 ilii and part of the pubis, and a lower pelvic 

 part, consisting of Ischium with a large pro- 

 portion of pubis and a very small amount of 

 Ilium. The ventral surface of the Ilium is 

 slightly concave, looking upwards and forwards 

 and inwards, and forming the bony Iliac fossa 

 giving origin to and covered by Iliacus. The 

 wall of the true pelvis, or lower portion of the 

 bone, is concave from before backwards, and is 

 mainly covered by Obturator internus, which 

 also arises from it : above this muscle, how- 

 ever, is a deep groove leading to the top of the 

 obturator foramen, and below it, on the inner 

 side of the tuberosity of the Ischium, is a rough 



falciform ridge for the attachment of the falciform process of the great sciatic ligament. S*^ 1 

 The Ischio-pubic ramus is seen, from this aspect, to have its lower part everted, afford- 

 ing an area for attachment of the crus penis or clitoridis. 



The Ilio-pectineal line, traced on to the upper ramus of the pubis, presents secon- 

 dary ridges, and the main part of these, made by Gimbernat's ligament, turns forward 

 to run into the spine of the pubis : other parts are directed internal to this, as will be 

 described later. 



The Levator ani arises from the back of the body of the pubis, from the inner side 

 of the ischial spine, and from the fascia covering the Obturator internus between these 

 points. It follows, therefore, that below a line drawn between these bony points the 

 Ischio-pubic portion is in relation with and gives attachment to structures in the 

 perineal and Ischio-rectal regions, while above this line its relations are with structures 

 in the pelvic cavity. 



It is convenient now, before proceeding to a more detailed examination of these 

 bones, to consider the general structure of the pelvis. For this purpose the complete 

 skeleton may be used, but it is advisable to have in addition an articulated pelvis 

 with the ligaments in situ. 



FIG. 97. Pubic part of right bone from the 

 front. 





