THE PELVIS 



177 



The average measurements of the diameters of the minor pelvis in the three planes are 

 given below: — 



Inlet.. 

 Cavity 

 Outlet . 



Conjugate or 

 Antero-posterior. 

 4i inches (10.6 cm.) 

 4f " (11.8 cm.) 

 3f " (9.0 cm.) 



Oblique. 

 inches (12.5 cm.) 

 " (13.0 cm.) 

 (11.2 cm.) 



Transverse. 

 inches (13.0 cm.) 

 (11.8 cm.) 

 " (10.6 cm.) 



Fig. 213. — Male Pelvis. (Lateral view.) 



Fig. 214. — Female Pelvis. (Lateral view.) 



There is, however, a difference between the sexes, the diameters of the male pelvis in 

 general averaging slightly less, and those of the female slightly greater than the figures above 

 given. 



Differences according to sex. — -There is a marked difference in the size and form of the 

 male and female pelvis, the pecularities of the latter being necessary to qualify it for its func- 

 tions in parturition. The various points of divergence may be tabulated as follows: — 



Male. 

 Bones heavier and rougher. 

 Ilia less vertical. 

 Iliac fossae deeper. 

 Major pehas relatively wider. 

 Minor pelvis deeper. 



" " narrower. 

 Superior aperture more heart-shaped. 

 Symphysis deeper. 

 Tuberosities of ischia infiexed. 

 Pubic angle narrow and pointed. 

 Margins of ischio-pubic rami more everted. 

 Obturator foramen oval. 

 Sacrum narrower and more curved. 

 Capacity of minor pelvis less. 



Female. 

 Bones more slender. 

 Ilia more vertical. 

 Iliac foss£e shallower. 

 Major pelvis relatively narrower. 

 Minor pelvis shallower. 



" " wider. 

 Superior aperture more oval. 

 Symphj^sis shallower. 

 Tuberosities of ischia everted. 

 Pubic arch wider and more rounded. 

 Margins of ischio-pubic rami less everted. 

 Obturator foramen triangular. 

 Sacrum wider and less curved. 

 Capacity of minor pelvis greater. 



The sexual characters of the pelvis as shown by A. Thomson are manifest as early as the 

 fourth month of foetal life. 



Quite recently attention has been drawn by D. Derry to some special points in which the 

 OS coxae differ in the two sexes, and two figures are shown here in which one of these points is 

 clearly brought out. It will be seen that the great sciatic notch is larger in the female, and 

 that the sacrum projects less forward at i+s apex. Moreover the facies auricularis is smaller 

 whilst below and in front of this surface, the sulcus 'preauricular is, a depression for the attach- 

 ment of the ligamenta sacroiliaca anteriora, is usually more pronounced. 



In comparison with the pelves of lower animals, which, speaking generally, are elongated 

 and narrow, the human pelvis is characterised by its breadth, shallowness, and great capacity. 

 Differences are also to be recognised in the form of the pelvis in the various races of mankind, the 

 most important being the relation of the antero-posterior to the transverse diameter, measured 



at the inlet. This is expressed by the pelvic index = ^— = — r. : 



transverse diameter 



In the average European male the index is about 80; in the lower races of mankind, 90 to 95. 



Pelves with an index below 90 are platypellic, from 90 to 95 are mesatipellic, and above 95 



dolichopellic. (Sir William Turner.) 



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