88 OSTEOLOGY. 



is oval in outline, its long diameter being directed downwards, 

 backwards, and inwards. It is formed entirely by the pubis and 

 ischium, and possesses smooth margins, and thick, excej^t where 

 they are formed by the pubis. 



The inlet, or briTn of the pelvis, is bounded superiorly by 

 the sacral promontory, laterally by the ilio-pectineal line, and 

 inferiorly by the crest and symphysis of the pubis. The aper- 

 ture thus defined inclines downwards and backwards, being 

 somewhat ovoid in form. The diameters of the inlet vary 

 according to the age and sex of the animal ; in the adult male, 

 the verticle or sacro-pubic diameter is a little less than the 

 transverse. 



The outlet, or 'posterior aperture, is somewhat triangular in 

 form, and is bounded above, at its apex, by the first coccygeal 

 bone, laterally by the sacro-sciatic ligaments, and inferiorly, by 

 the ischia and ischiatic spines. Its vertical diameter, from the 

 last sacral or first coccygeal segment, to the ischiatic symphysis, 

 is less than the transverse, taken between the ischiatic spines. 

 The length, taken from the middle of the lateral part of the inlet 

 to the ischiatic tuberosity, is usually about equal to the transverse 

 diameter of the inlet. 



FEMALE PELVIS. 



The size and proportions of the pelvis differ considerably with 

 the sex of the animal. Bearing in mind that we have referred 

 hitherto to the pelvis of the adult male, the differences in that 

 of the female may be thus summarised : — The whole structure 

 is larger. The transverse diameters above named, in fact, the 

 transverse measurements generally, are very large, the former 

 exceeding the vertical diameters by a much larger difference 

 than is found in the male. The internal border of the ilium is 

 more hollowed out, and smoother. The ischial arch is large, and 

 it presents a concave border, tending but slightly to form an 

 angle at the symphysis. The cotyloid cavities are wider apart 

 than in the male, while the obturator foramina are larger and 

 more circular in form. 



PELVIC LIMB. 



The bones of the pelvic or hind extremity are the femur, patella, 

 tibia, and fibula; the bones of the tarsus — viz., the astragalus, 

 OS calcis, cuboid and three cuneiform bones ; one large and two 

 small metatarsals ; three phalanges and three sesamoids. See p. 65. 



