THE PELVIS AND THE VISCERA 127 



supporting the body weight is not to be doubted, despite 

 some apparent contradictions, and it is to be remarked 

 that in animals in which the body weight is not borne at 

 all upon the hind-limbs (as in the Bats, etc.) no portion 

 of the pelvic girdle meets in the mid-ventral line, and 

 consequently no symphysis is developed. 



FIG. 45. PURELY DIAGRAMMATIC REPRESENTATION OF THE 



PELVIS OF AN ORTHOGRADE MAMMAL. 

 Note the way in which the sacrum articulates with the ilia at the 



sacro-iliac joint, and the meeting of only a small area of the 



pubes at the pubic symphysis. 



The pelvis has now, in its altered relation to the hind- 

 limb, an entirely .different mechanical design. There is 

 a main weight-supporting arch behind, composed of the 

 ilia, with the sacrum as the keystone of this arch. A 

 subsidiary weight-suppoT^mg'afch~is~Heveloped in front, 

 and this is represented by the subpubic arch. The old 

 ventro-dorsal weight-supporting arch is superseded, and 

 now the cavity of the pelvis need no longer be moulded 



