PELVIS. 



115 



projection called the anterior inferior spinous pro- 

 cess (d), the two being separated by a smoothly 

 edged notch (). Below the inferior spine is 

 another indentation, wider and less deeply 

 marked, and forming part of the overhanging 

 edge of the cavity for the thigh bone, and 

 in which a muscle lies. To this succeeds be- 

 low, another rounded, less strongly marked 

 prominence, in which the ilium and pubes 

 are united, called the ilio-pcctineal eminence 

 (e). From this point commences the ob- 

 lique or inward direction of this border, 

 which is for about two inches smooth and 

 rounded for a muscle to glide over, and then 

 presents a fourth well marked, acute, forward 

 projection called the spine of the pubis (/), 

 which is continued by a rough strongly marked 

 ridge, the crest of the pubi* (/, g), to the ter- 

 mination of this border in an abrupt right 

 angle, the angle of the pubis (g). All these 

 eminences result from the implantation of the 

 tendons of muscles of the leg or abdomen. 



The inferior border, composed partly by the 

 pubis, but principally by the ischium, here 

 commences. It is arranged first in a rough, 

 indented, plane, oval, and vertical surface, 

 which in the living bone is united by fibro- 

 cartilage to innominate bone of the opposite 

 side, and forms the symphysis of the pubis ; 

 avfityvfit, to grow together (h). The posterior 

 border of this articular surface is often raised 

 into a ridge, projecting backwards, especially 

 in old persons. Cruveilhier mentions one, 

 observed in a woman who had borne many 

 children, where this was a perfect crest. Be- 

 low this point the border assumes a direction 

 tending first downwards and outwards, and 

 then, somewhat sharply, curving upwards and 

 backwards. Just below the symphysis it pre- 

 sents a sharp, rough, irregular ridge, with a 

 considerable outward eversion, affording attach- 

 ment to strong fasciae and muscles of the leg 

 and perineum, and to the root of the penis. 

 At the most depending part it gradually widens 

 into a very rough, large, elongated, and rounded 

 tuberosity, 3 inches long by 1^ broad at its 

 posterior extremity, the tuberosity of the ischium 

 (). This tuberosity has a general inclination 

 outward ; and along its inner margin, which 

 projects lower than the outer, is a raised ridge 

 for the attachment, of the great sciatic liga- 

 ment. Upon it are implanted the large pos- 

 terior leg muscles, and in the sedentary posi- 

 tion the trunk is supported by it. Hence the 

 name of this portion of bone (from irr^fiv 

 KaQn/ttrog quod sustineat sedentes), and also 

 its German appellation (Sitzbein or Sitz- 

 stiick). 



The posterior border commences above this 

 tuberosity. Its direction is first vertical, and 

 then irregularly horizontal. It is formed by 

 the ischium and ilium. Above the tuberosity 

 of the ischium is a rounded groove, in the 

 fresh state covered by cartilage, and called the 

 small sciatic or obturator notch (k), over which 

 a muscle glides. Then occurs a sharp pro- 

 minent process, turned considerably inwards, 

 giving attachment to a strong ligament and 

 some muscles, and called the spine of the ischium 



(/). Above this the border is thin, rounded' 

 and vertical, becoming gradually much thicker 

 and finally curving sharply backwards and 

 downwards. It thus forms a large notch, the 

 great sciatic, formed principally by the ilium (?). 

 To this succeeds a tapering, elongated, and 

 depending prominence called the posterior in- 

 ferior spinous jjrocess of the ilium (n\ serving 

 for the attachment of ligaments. The border 

 then presents an insignificant rounded notch, 

 with a thin edge; and finally terminates in 

 the superior border at the postovor superior 

 iliac spine, already described. 



Fig. 76. 



External view of the innominate bone. 



The external or femoral surface of the os 

 innominatum {fig. 76.) at its upper or iliac 

 portion is directed outwards, backwards, and 

 slightly downwards ; at its central part out- 

 wards ; while its pubic and ischiatic or lower 

 part is directed forwards, downwards, and out- 

 wards. The iliac portion is broad and fan- 

 shaped above, whence this upper portion is 

 called the ala or wing of the ilium. It is convex 

 at its anterior, and concave at its posterior por- 

 tion, following the/curve of the crest before 

 mentioned. The concavity is termed by many 

 writers the external iliac fossa. The convexity 

 is increased by a ridge of thick bone, which 

 passes vertically downwards from the thick- 

 ened portion of the crest to the cavity for the 

 thigh bone. At the posterior part of this 

 surface, close to the termination of the crest, 

 is an elongated rough impression of a some- 

 what triangular shape, having its base at the 

 superior and inferior posterior spines, and 

 tapering off gradually along the crest for about 

 three inches, which marks the origin of a 

 great muscle thegluteus maximus.and which 

 may be called the glutcal impression ( I ). In the 

 middle of this surface is a slightly marked 



I 2? 



