118 PELVIS. 



the symphysis pubis, expanded on each side, and encroached upon be- 

 hind by a projection of the upper part of the sacri m, which is named the 

 promontory. The cavity is somewhat encroached upon at each side by a 

 smooth quadrangular plane of bone, corresponding with the internal sur- 

 face of the acetabulum, and leading to the spine of the ischium. In front 

 are two fossae around the obturator foramina, for lodging the obturator 

 internus muscle, at each side. The inferior termination of the pelvis is 

 very irregular, and is termed the outlet. It is bounded in front by the 

 convergence of the rami of the iscnTum and pubes, which constitute the 

 arch of the pubes ; on each side by the tuberosity of the ischium, and by 

 two irregular fissures formed by the greater and lesser sacro-ischiatic 

 notches ; and behind by the lateral borders of the sacrum, and by the 

 coccyx. 



The pelvis is placed obliquely w r ith regard to the trunk of the body, so 

 that the inner surface of the ossa pubis is directed upwards, and would 

 support the superincumbent weight of the viscera. The base of the sacrum 

 rises nearly four inches above the level of the upper border of the sym- 

 physis pubis and the apex of the coccyx, somewhat more than half an 

 inch above its low r er border. If a line were carried through the central 

 axis of the inlet, it would impinge by one extremity against the umbilicus, 

 and by the other against the middle of the coccyx. The axis of the inlet 

 is therefore directed downwards and backwards^ while that of the outlet 

 points downwards and forwards, and corresponds with a line drawn from 

 the upper part of the sacrum, through the centre of the outlet. The axis 

 of the cavity represents a curve, wilich corresponds very nearly with the 

 curve of the sacrum, the extremities being indicated by the central points 

 of the inlet and outlet. A knowledge of the direction of these axes is 

 most important to the surgeon, as indicating the line in which instruments 

 should be used in operations upon the viscera of the pelvis, and the direc- 

 tion of force in the removal of calculi from the bladder ; and to the accou- 

 cheur, as explaining the course taken by the foetus during parturition. 



There are certain striking differences between the male and female pel- 

 vis. In the male the bones are thicker, stronger, and more solid, and the 

 cavity deeper and narrower. In the female the bones are lighter and 

 more delicate, the iliac fossae are large, and the ilia expanded ; the inlet, 

 the outlet, and the cavity, are large, and the acetabula farther removed 

 from each other ; the cavity is shallow, the tuberosities widely separated, 

 the obturator foramina triangular, and the span of the pubic arch greater. 

 The precise diameter of the inlet and outlet, and the depth of the cavity, 

 are important considerations to the accoucheur. 



The diameters of the inlet or brim are three : 1. Antero-posterior, sacro- 

 pubic or conjugate ; 2. transverse ; and 3. oblique. The antero-posterior 



of the sacrum. 4. The anterior surface of the sacrum, on which its transverse lines and 

 foramina are seen. 5. The tip of the coccyx. C, G. The iliac fossae, forming the lateral 

 boundaries of the false pelvis. 7. The anterior superior spinous process of the ilium; 

 left side.* 8. The anterior inferior spinous process. 9. The acetabulum. a. The notch 

 of the acetabulum. b. The body of the ischium. c. Its tuberosity. d. The spine of the 

 ischium seen through the obturator foramen, e. The os pubis. f. The symphysis pubis. 

 g. The arch of the pubes. h. The angle of the os pubis. i. The spine of the pubes ; the 

 prominent ridge between h and i is the crest of the pubes. k, k. The pectineal line of 

 the pubes. Z, 1. The ilio-pectineal line; m, m. the prolongation of this line to the pro- 

 montory of the sacrum The line represented by h, i, A;, k. /, I. and m,m. is the brim of 

 the true pelvis, n. The ilio-pectineal eminence, o. The smooth surface which supports 

 the femoral vessels, p, p. The great sacro-ischiatic notch. 



