432 ilE. ST. GEOKGE MIVAET ON THE 



Within the line of these ribs is to be seen a very large ventral arch, each side or 

 lateral half of which is bent at an angle into a dorsal and ventral division or limb, which, 

 when viewed preaxially, appears as follows : — 



The dorsal division, or limb, consists mainly of the pubic bone (j)}, which diverges from 

 its fellow of the opposite side at an angle of about 66°. The external margin of this 

 limb is, in the main, concave externally ; but the outline is interrupted by the more 

 distant jutting out of the posterior part (i) of the ischium. The internal margin of the 

 dorsal limb is convex, but with its outline interrupted, and the convexity exaggerated 

 by the projecting inwards (/') of the more anterior part of the ischium. 



The ventral division or limb is bent inwards cm the dorsal limb (of the same half of 

 the great ventral arch) at an angle of about 115°, and consists of the pubis, which ter- 

 minates ventrally by meeting its fellow in (si/) a ventral symphysis. 



The external margin of this ventral division is concave ; its internal margin is convex. 



Wlien the pelvis is viewed postaxially the same great ventral arch is seen to be con- 

 nected dorsally with a pentagonal mass, one angle of which is dorsad, and which has in 

 its midst the postaxial surface of the small twenty-second sacral vertebra, i. e. the forty- 

 seventh vertebra of the whole spinal column. 



The two dorsal sides of the pentagon meet at an angle of about 118°; and the margin 

 of each, from the point of junction outwards, is slightly concave, then more strongly 

 convex, then still more sharply concave, the sharp concavity being produced by the pro- 

 minence of the antitrochanteric process. Each of these dorsal sides is formed by an 

 ilium. 



From the tip of this last-mentioned process each lateral margin of the pentagon pro- 

 ceeds ventrad, forming with the adjacent dorsal side an angle of about 90°; its margin 

 is, for its greater part, gently concave, and is formed by the ischium ; it forms with the 

 ventral side of the pentagon an angle of about 120°. 



This ventral side of the pentagon is formed by the pubes, and is more or less 

 horizontal. 



When the pelvis is viewed laterally (fig. 71), the sacrum being horizontal, we have a 

 dorsal elongated mass (made up of the ilium and sacrum) something like the skull of a 

 bird, with the tip of the beak turned postaxially, from which two long bars of bone 

 (i & p) diverge ventrally and proceed postaxiad to join and end in a great recurved 

 process (s y). 



These bars proceed from beneath the acetabulum. 



The acetabulum is placed on the ventral side of the ilio-sacral mass, so that its postaxial 

 margin is on the preaxial side of the middle point of that elongated mass. 



Within the acetabulum are to be seen the four slender, dorsally and preaxially 

 extended diapophyses of the thirty-second, thirty-third, thirty-fourth, and thirty-fifth 

 vertebrae. 



The dorsal margin of the preacetabular part of the ilium forms the roof of the cranial 



