THE PELVIS 111 
(Diameter transversa) is measured at the greatest width, 7. e., just above the psoas 
tubercle. 
The posterior aperture or outlet of the pelvis (Apertura pelvis caudalis) is 
much smaller and is very incomplete in the skeleton. It is bounded dorsally by the 
Fic. 89.—Petvic Bones or Station; Front View. 
C, Conjugate, D.t., transverse diameter of pelvic inlet. 
Fic. 90—Petyvic Bones oF Mare; Front View. 
C, Conjugate, D.t., transverse, diameter of pelvic inlet. 
third coccygeal vertebra and ventrally by the ischial arch; in the fresh state it is 
completed laterally by the sacro-sciatic ligament and the semimembranosus muscle. 
The axis of the pelvis is an imaginary line drawn through the centers of the 
inlet, cavity, and outlet. 
Sexual Differences.—Marked differences exist in the size and form of the pel- 
vis in the two sexes. The average conjugate diameter is about 9! inches (ca. 23 to 
