128 



PELVIS. 



count of the wavy outline and oblique direc- 

 tion of the innominate bones. It is upon 

 these tuberosities only, consequently, that the 

 trunk rests in the sitting posture, and not 

 upon a tripod formed by them and the coccyx, 

 as has been erroneously supposed by some 

 older writers. The boundaries of the inferior 

 outlet, from the same cause, do not, like those 

 of the superior, lie all in one plane or level, 

 but are bent, as it were, at the ischial tuber- 

 osities, into two planes ; an anterior, termin- 

 ated by, and nenrlyin a line with, the symphysis 

 pubis, looking downwards and a little for- 

 wards ; and a posterior, terminated by and in- 

 cluding the coccyx, directed downwards and 

 backwards, parallel with the superior pelvic 

 plane, but varying with the extension of the 

 coccyx downw'ards. The plane of this outlet, 

 however, is usually considered to be marked 

 by a straight line joining the lower border of 

 the symphysis pubis and the tip of the coccyx ; 

 and its general direction to coincide with a 

 line drawn perpendicular to this plane down- 

 wards and backwards. 



Differences of the jie/vis in the sexes. Of 

 all the bones in the human skeleton, those of 

 the pelvis offer the most distinct characters 

 between the male and female sex. 



In the female (fig. 83.), the bones are 

 lighter, shorter, and broader, less evidently 

 marked by tuberosities and indentations re- 

 sulting from the attachments of the tendinous 

 structures, and have in a less degree the 

 peculiarities, before described, of the articu- 

 lations, as well as those resulting from their 

 peculiar mechanism. The iliac crest is less 

 arched, and presents less distinctly the .S'-like 

 curve, the iliac wings are thinner and more 

 expanded, and the internal iliac fossce larger, 

 mare shallow, and directed more anteriorly, 

 and the iliac ridge extending between the 

 cotyloid and sacro-iliac joints is less massy, 

 less suddenly arched, and longer. The ischia 

 do not converge so much towards the inferior 

 outlet, and with the tuberosities are less massy, 

 wider apart, and shorter, and the spines are 

 less marked, and directed less inwards, and 

 the transverse diameter of the inferior strait 

 is greater. The ascending branches and the 

 descending branches of the pubcs are thinner, 

 narrower, and more oblique, turn their inner 

 borders more forwards, and at the same time 

 afford a more rounded expansion to the 

 pubic arch, at the expense of the obturator 

 foramina, which are thereby rendered smaller 

 and more triangular in the female. The 

 symphysis of the puhis is not so deep, and the 

 fibro-cartilage is wider, thicker, and more 

 vertical in position ; the united angles are 

 more flattened posteriorly, and the horizontal 

 branch is longer, thinner, and directed more 

 transversely outwards, rendering the distance 

 between the symphysis and the cotyloid cavity, 

 and consequently the projection of the hips 

 greater, and an increased transverse diameter 

 of the brim. 



The sacrum is wider and less arched trans- 

 versely, and its promontory does not so much 

 overhang the pelvic cavity, and thus the su- 



perior outlet has less of the heart shape, 

 being in females more properly termed oval. 

 This difference of shape is also contributed 

 to by the less lateral obliquity of the superior 

 branch of the pubes. 



Whether the sacrum is less arched trans- 

 versely in the female, I endeavoured to 

 ascertain by observations taken from eighteen 

 subjects, of which half were male and 

 half female. A strip of lead ith of an 

 inch thick was made to assume the form 

 of the transverse curve of the sacrum, 

 by being pressed across the anterior surface 

 just below the promontory, and the breadth 

 from one sacro-iliac joint to the other care- 

 fully marked off. From this, a line was 

 drawn on paper, following the curvature re- 

 tained by the lead, the extremities of which 

 line were joined by a straight line, forming a 

 chord to the sacral arc. The distance of the 

 centre of this chord from the centre of the 

 sacral curve was then measured. In the nine 

 males, the height of the arch thus obtained 

 varied from six to nine lines ; in the nine 

 females, five to nine lines, the greatest num- 

 ber of the males being seven lines, and the 

 greatest number of the females being six lines. 

 In the single case of the female where the 

 measurement was nine lines, the subject was 

 old. When we consider, that in the great 

 majority of instances the breadth of the 

 sacrum measured along the curve was greater 

 by i to ^ an inch in the female, these results 

 will yield a still greater relative depth to the 

 transverse sacral curve of the male. 



Besides this transverse arch, the vertical 

 curvature of the sacrum is relatively much less 

 in the female. This is more apparent in the 

 direction of the three upper sacral pieces, 

 which are generally little curved, and often 

 almost plane in the female, while, in the male, 

 the curve is most apparent in the centre 

 and more uniformly distributed over the 

 whole sacral surface. Upon this point, how- 

 ever, much difference of opinion prevails 

 amongst anatomists ; Meckel and Ward agree- 

 ing with the opinion here enunciated, while 

 Cloquet and Cruveilhier maintain that the 

 curvature of the sacrum in the female is 

 deeper and more regular. The experiments 

 of Mr. Ward, however, correspond more 

 entirely with my own observations on this 

 point. Mr. Ward observes, in addition, that 

 the male sacrum often approaches the form 

 of the female, but the female rarely to that of 

 the male. In old women, however, I have often 

 seen a great vertical curvature of the sacrum. 



The coccyx is more moveable, more fre- 

 quently in several jointed pieces, less pro- 

 jected forwards, and less frequently ankylosed 

 to the sacrum in the female. 



The sacro-scialic notches in the female are 

 wider and not so deep as in the male ; the dis- 

 tance from the ischiadic spine and tuberosity 

 to the sacrum and coccyx being greater, and 

 the sacro-sciatic ligaments longer and more 

 slender. 



The peculiarities above mentioned give 

 to the female pelvis a wider, shallower, more 



