THE PEL VIS 217 



pectineal line. The cavity is shallow in front, measuring at the symphysis an 

 inch and a half in depth, three inches and a half in the middle, and four 

 inches and a half posteriorly. From this description it will be seen that the cavity 

 of the pelvis is a short, curved canal, considerably deeper on its posterior than 

 on its anterior wall. This cavity contains, in the recent subject, the rectum, 

 bladder, and some of the organs of generation. The rectum is placed at the back 

 of the pelvis, and corresponds to the curve of the sacrococcygeal segment of the 

 vertebral column; the bladder in front, behind the symphysis pubis. In the female 

 the uterus and vagina occupy the interval between these viscera. 



The lower circumference is very irregular; the space enclosed by it is called 

 the outlet (apertura pelvis inferior). It is bounded by three prominent emi- 

 nences one posterior, formed by the point of the coccyx; and one on each side, 

 the tuberosities of the ischia. These eminences are separated by three notches; 

 one in front, the pubic arch (arcus pubis}, formed by the convergence of the rami 

 of the ischia and pubic bones on each side. The other notches, one on each side, 

 are formed by the sacrum and coccyx behind, the ischium in front, and the ilium 

 above; they are called the sacrosciatic notches; in the natural state they are converted 

 into foramina by the lesser and greater sacrosciatic ligaments. In the recent 

 state, when the ligaments are in situ, the outlet of the pelvis is lozenge-shaped, 

 bounded in front by the subpubic ligament and the rami of the os pubis and ischium; 

 on each side by the tuberosities of the ischia; and behind by the great sacrosciatic 

 ligaments and the tip of the coccyx. 



The diameters of the outlet of the pelvis are two, antero-posterior and trans- 

 verse. The antero-posterior diameter extends from the tip of the coccyx to the 

 lower part of the symphysis pubis; its average measurement is three and three- 

 quarter inches in the male and four and one-half inches in the female. The 

 antero-posterior diameter varies with the length of the coccyx, and is capable 

 of increase or diminution on account of the mobility of that bone. During labor 

 the coccyx may be bent back so that the conjugate is increased one inch, or even 

 one and one-fourth inches. The transverse diameter extends from the posterior 

 part of one ischiatic tuberosity to the same point on the opposite side; the average 

 measurement is three and one-half inches in the male and four and three-fourths 

 in the female. 1 



Position of the Pelvis. In the erect posture the pelvis is placed obliquely with 

 regard to the trunk of the body; the bony ring, which forms the brim of the true 

 pelvis, is placed so as to form an angle of about 60 to 65 degrees with the ground 

 on which we stand (inclinatio pelvis]. The pelvic surface of the symphysis 

 pubis looks upward and backward, the concavity of the sacrum and coccyx down- 

 ward and forward, the base of the sacrum in well-formed female bodies being 

 nearly four inches above the upper border of the symphysis pubis, and the apex 

 of the coccyx a little more than half an inch above its lower border. In conse- 

 quence of the obliquity of the pelvis the line of gravity of the head, which passes 

 through the middle of the odontoid process of the axis and through the points 

 of junction of the curves of the vertebral column to the sacrovertebral angle, 

 descends toward the front of the cavity, so that it bisects a line drawn transversely 

 through the middle of the heads of the thigh bones. And thus the centre of gravity 

 of the head is placed immediately over the heads of the thigh bones on which the 

 trunk is supported. 



i The measurements of the pelvis given above are, I believe, fairly accurate, but different measurements are 

 given by various authors, no doubt due in a great measure to differences in the physique and stature of the 

 population from whom the measurements have been taken. The accompanying chart has been formulated to 

 show the measurements of the pelvis which are adopted by many obstetricians. [EDITOR.] 



DIAMETERS or THE TRUE PELVIS IN WOMAN. 



Antero-posterior. Oblique. Transverse. 



Of inlet . . 48/5 inches (118 mm.) 5 inches (127 mm.) 5'/4 inches (135 mm.) 



Of outlet . . 4>/ 2 inches (115 mm.) 4 3 4 inches (120 mm.) 



