THE PELVIS. 



H7; 



recent state 'by the great sacro-sciatic ligaments, which therefore assist in bounding 

 the outlet of the pelvis. 



Position of the pelvis. In the erect attitude of the body, with the heels 

 in contact and the toes directed outwards, the pelvis is so inclined that the plane of 



Fig. 129. MEDIAN SECTION OF A FEMALE PELVIS. 

 (Reduced from Nagele. ) $ 



1, symphysis pubis ; 2, promontory of the 

 sacrum ; 3, coccyx ; 4, anterior superior spine 

 of ilium ; 5, tuberosity of ischium ; 6, spine of 

 iscbium (the thyroid foramen is not represented so 

 pointed below as it generally is in females). The 

 vertical and horizontal lines in the lower part of 

 the figure will assist the eye in judging of the 

 degree of inclination of the pelvis, as illustrated 

 by the next figure. 



the brim of the true pelvis forms an angle 

 with the horizontal, which varies in differ- 

 ent individuals from 50 to 60. The base 

 of the sacrum is then about 3|- inches above 

 the upper margin of the symphysis pubis, 

 and the tip of the coccyx from half an 

 inch to an inch above the apex of the sub- 

 pubic arch. The inclination of the pelvis 

 varies with the position of the lower limbs, and the angle is generally somewhat 

 greater in the female than in the male. 1 The pelvic surface of the sacrum, near its 

 base, looks much more downwards than forwards, hence the sacrum, appears at first 

 sight to occupy the position of the keystone of an arch ; but being in reality broader 



Fig. 130. SKETCH OF PART OF THE PRECEDING 



FiaURE, SHOWING THE INCLINATION OP THE 

 BRIM OF THE PELVIS AND ITS AXIS IN THE 

 ERECT POSTURE. ^ 



a, b, line of inclination of the brim of the true 

 pelvis ; e, f, a line inclining backwards and up- 

 wards, touching the lower edge of the symphysis 

 pubis and point of the coccyx ; c. d, axis of the 

 brim at right angles to the plane of the brim ; 

 d, h, g, curved axis of the cavity and outlet. 



at its pelvic than on its dorsal aspect, it is a 

 keystone inverted, or having its broad end 

 lowest, and is supported in its place chiefly 

 by ligaments, but also to a slight extent 

 by the inward projection of the anterior 

 margin of the iliac articular surface.' The 

 line of pressure of the weight of the body 

 on the sacrum is directed downwards to- 

 wards the symphysis pubis, and the resistance of the head of the thigh-bone on each 

 side is directed upwards and inwards. 



The axis of the pelvis is the name given to a line drawn at right angles to 

 the planes of the brim, cavity and outlet, through their central points. The 



1 Nfigele, "Das weibliche Becken," &c., 1825 ; Wood, art. "Pelvis," in Cyclop, of Anat. and 

 Phys. ; G. H. Meyer, Arch. f. Anat., &c., 1861; Fiirst, "Die Maass- und Neigungs-Verhaltnisse des 

 Beckens," 1875. 



