PELVIS. 



129 



open, and less massy appearance than that 

 of the male, and give rise to a still more im- 

 portant distinction derived from the measure- 

 ments from one point to another, and from 

 the relative diameters of the cavity and out- 

 lets of the pelvis. Another distinction will 

 be presently found in the relative angles which 

 the sacrum and whole pelvis form with the 

 axis of the spinal column, and this again will 

 influence the relative direction of the axes of 

 the cavity and outlets. 



Fig. 83. 



Anterior view of the female pelvis, with lines of 

 m eas urement. 



a b, conjugate diameter of brim; c d, diagonal 

 ditto ; ef, transverse ditto ; g h, transverse diameter 

 of inferior outlet. 



Tlie measurements of the pelvis. The most 

 evident distinctions between the adult pelves 

 of the sexes are derived from their com- 

 parative dimensions, and result from the im- 

 portant bearing they have upon the me- 

 chanism of parturition in the female. For 

 this purpose, an average is taken from the 

 measurements of many well-formed pelves, 

 and one with the average results is adopted 

 as the standard pelvis. 



The measurements referring to the width 

 of the pelvis are commonly spoken of as the 

 diameters of the pelvis. They are taken at 

 the brim, in the cavity, and at the inferior 

 outlet, and are usually an anterior-posterior 

 or conjugate, two diagonal or oblique, and a 

 transverse. 



At the brim of the pelvis, the antero-pos- 

 terior or conjugate diameter is the distance 

 between the upper part of the posterior sur- 

 face of the symphysis pubis and the pro- 

 montory of the sacrum (a, b, jig. 83.); the 

 oblique, between the point of the brim nearest 

 the pectineal eminence and the sacro-iliac 

 joint of the opposite side (c, d) ; and the 

 transverse diameter is the distance between 

 the ilia at a point halfway between the sacro- 

 iliac joint and pectineal eminence (e,f). 



In the cavity, the antero-posterior diameter 

 extends between the centre of the pubic sym- 

 physis, and the body of the third piece of the 

 sacrum; while the oblique and transverse 

 correspond to those of the upper outlet, 

 on the same plane. 



At the inferior strait, the antero-posterior 

 extends from the lower extremity of the 

 Supp. 



symphysis pubis to the tip of the coccyx ; 

 and the transverse, from the middle of the 

 inner border of one ischiadic tuberosity to the 

 other (g, //). An oblique diameter at the 

 inferior outlet is not one commonly given by 

 writers, although possessed of some import- 

 ance in certain cases of deformity. In the table 

 on the next page, there is the average of six 

 measurements taken on the recent subject, 

 before the shrinking of the ligaments, from 

 the centre or junction of the ischio-pubic 

 rami to the centre of the great sciatic liga- 

 ment opposite. The antero-posterior diameter 

 of this strait is capable of much increase by 

 the mobility of the coccyx, which will also 

 affect, in some measure, the oblique diameters, 

 in an opposite degree, from the stretching of 

 the great sciatic ligaments, a point which I 

 think has scarcely been sufficiently noticed 

 by accoucheurs. 



Besides these, the distances between many 

 other points may be of great importance to 

 the accoucheur. Such are those pointed 

 out by Naegele, to be presently noticed ; the 

 distances between the spines of the ischia, 

 so much greater in the female ; and another, 

 which I have not hitherto seen definitively 

 given, viz. the distance between the lower 

 edge of the symphysis pubis and the sacral 

 promontory, a measurement of considerable 

 importance in the use of pelvimeters, to 

 ascertain the conjugate diameter of the brim. 

 This may be called the lower or inclined 

 conjugate diameter, and it will be found to 

 be, in most instances, half an inch more than 

 the direct or superior conjugate diameter, 

 being, in fact, the longest side of a triangle, 

 having the conjugate diameter, and the breadth 

 of the pubic symphysis for the other sides. 

 The measurement of the circumference of the 

 brim of the pelvis, and the proportion con- 

 tributed to it by the sacrum, ilia and pubes 

 respectively, announce a manifest difference 

 between the pelves of the two sexes. 



In glancing over the appended table, it will 

 be seen that the male pelvis exceeds the female 

 in most of its vertical dimensions, while the 

 female pelvis is larger in the horizontal di- 

 ameters. The depth of the true pelvis, 

 however, measured at the sacro-coccygeal 

 column, is greater in the female, on account 

 of the greater size of the sacrum in that sex, 

 and also because of the less total vertical 

 curvature. The depth from the pectineal 

 eminence to the lowest point of the ischiadic 

 tuberosities laterally, and at the pubic sjm- 

 physis anteriorly, show, on the contrary, a 

 great superiority in the male ; as also does 

 the total depth of the whole pelvis, from the 

 highest point of the ilium to the most de- 

 pending part of the ischium, while the width 

 between the iliac spines and crests are much 

 greater in the female. The horizontal dia- 

 meters of the pelvis may be said to depend 

 upon the ilio-pubic element^ while the depth 

 or vertical measurement depends solely on 

 the ilio-ischion clement, so that, in the female, 

 the former may be considered to prevail, and 

 in the male, the latter element. This is re- 



