134 



PELVIS. 



In twenty-five males, 



Nine were from 11 6 to 112, five from 115 

 to 117, nine from 120 to 125, and two only 

 130. 



In twenty-five females, 

 Nine were from 120 to 125, eight from 

 128 to 130, five from 133 to 140, two were 

 145, and one, an aged subject, 118 only. 



Fig. 84, 



Diagram (slightly altered from Naegele) of a well- 

 formed female pelvis, showing the angles of inclina- 

 tion and axes. 



From these we may deduce 117 as the 

 average sacro-vertebral angle in the male, and 

 130 as the same angle in the female. This 

 remarkable average difference of 13 shows 

 the much greater suddenness of the altera- 

 tion of direction in the spinal column at its 

 sacral extremity in the male subject, and is 

 much greater than the difference of 5 to 6 

 in the pelvic inclination of the sexes com- 

 pared in the tables of Weber and Naegele. 

 But, in order more clearly to ascertain it the 

 pelvic inclination invariably depended upon 

 the variations of the sacro-vertebral angle, I 

 compared the sacro-vertebral and pelvi- verte- 

 bral angles in nine male and nine female sub- 

 jects. In the former, I found the difference 

 between these angles to vary from 5 to 35, 

 and, in the latter, to vary from 5 to 25. In 

 one instance only, in a male, the sucro-verte- 

 bral was as large as the pelvi-vertebral angle. 

 From these observations, which were very 

 carefully taken, it would seem that the total 



pelvic inclination does not exactly depend upon 

 the sacro-vertebral angle ; and that, in males, 

 where the average pelvic obliquity is a little 

 greater, the average sacro-vertebral angle is 

 much and disproportionately less. These results 

 contradict, also, the assumption somewhat 

 indefinitely stated by Blumenbach and others, 

 on the authority of Bonaccioli, of Ferrara, 

 that the sacrum inclines more backward, and 

 that the sacro-vertebral angle is more promi- 

 nent in the female than in the male. 



If the long diameter of the pubic symphysis 

 be continued in its direction downwards and 

 backwards, it will, in a well-formed female 

 pelvis, cut the transverse vertical plane of the 

 spine, also prolonged, at an angle of 50 to 55 

 (^.84.a &&), which will be found to be about 

 the complementary or opposite angle to the 

 sacro-vertebral angle in the female. This 

 shows the general parallelism of the anterior 

 or pubic wall of the pelvis, with the upper 

 part of the posterior or sacral wall, although, 

 on account of the rapid thinning of the latter 

 as it descends, its pelvic surface seems to 

 diverge from the pubis. Naegele found the 

 anterior pelvic wall to be often at right angles 

 to the plane of the inlet, but the posterior 

 generally somewhat more than a right angle. 

 The great obliquity of the symphysis pubis to 

 the transverse vertical plane of the vertebrae is 

 one of the great characteristics of the human 

 pelvis, as will be seen hereafter in the consider- 

 ation of the comparative anatomy of the pelvis. 

 The angle formed by the symphysis pubis with 

 the horizon is given by Cuvier from 75 to 95. 

 This is much too large ; from 35 to 40 

 is the true angle of the symphysis with the 

 horizon in the human subject. 



Ilio-lschlal angle. While the pubis in the 

 human subject is continued in the same right 

 line with the mean direction of the ilium, 

 which coincides with the cotylo-sacral rib of 

 that bone, the ischium is inclined backwards^ 

 forming an angle of 1 10 to 115 with the same 

 rib of bone (see^g. .? 12. 1. a c d, page 73.), so 

 that, while the pubes are directed transversely 

 with regard to the pelvic cavity, the ischia are 

 directed vertically along, and forming the sides 

 of the cavity. This arrangement will also be 

 found to be an important characteristic of the 

 human pelvis, when compared with those of 

 the inferior mammalia, in which the reverse 

 of this arrangement will be found to prevail, 

 viz., the continuation of the ischia in the line 

 of the ilia, and the formation of an Mo-pubic 

 angle. 



Angle of IschiO'publc arch. The angle at 

 which the ischio-pubic rami tend toward each 

 other, has been placed by Watt at 60 to 80 

 in the male, and 90 in the female ; and by 

 Scemmerring at 75 for the male, and 95 for 

 the female (see Jigs. 83, 80.). 



AXES OF THE PELVIS. The term axis is 

 applied anatomically to the line of direction of 

 any surface or plane, and, as it implies a right 

 line, drawn at right angles to that surface 

 or plane, it can only be applied with propriety 

 to the outlets of the pelvis. As applied by 

 some authors to the line which indicates 



