96 '////: BONES. 



Tho inferior region is nearly horizontal. Formed by the pubes and isc-lii:i, 

 it presents from before to behind: 1, In the middle, the iBchio-jiuhic 

 syniphysis ; 2, On each side the subpnbic groove, the oval foramina, and 

 the inferior face of the ischia ; 3, Quito externally, the cotyloid cavities, by 

 which the pelvis rests on the posterior limbs. 



The lateral regions are oblique from above to below and within to 

 without, and wider in front than behind. They exhibit : 1, Tho spine of 

 the ilium and the two anterior spiuous processes; 2, The external iliac 

 fossa; 3, The ischiatic arch; 4, The supercotyloid crest or ischiatic spine, 

 which presents outwardly the surface of insertion for the internal or deep 

 gluteus muscles ; 5, The lesser ischiatic notch ; 6, The ischiatic tuberosity. 



Internal surface. Tho internal surface of the Horse's pelvis cannot bo 

 divided into two portions as in Man, because the inner aspect of the iliac bones 

 is not hollowed out to form an anterior cavity. 



The pelvis of Solipeds is, therefore, a simple conoid cavity, in which are dis- 

 tinguished four regions or faces, and two apertures called the inlet and outlet. 



The anterior opening or inlet is nearly circular, especially in the Mare, 

 and a little oblique downwards and backwards. It is limited above by tho 

 inferior face of the base of the sacrum ; inferiorly, by tho anterior border of 

 the pubis ; and on the sides by a portion of the inner face of the iliac bones, 

 and also the internal aspect of the pectineal crests. 



The inlet presents four diameters : a vertical, horizontal, and two 

 oblique. The first extends from tho inferior face of tho sacrum to tho 

 anterior border of the pubic symphysis ; its mean length is 8 inches. 

 The second is measured from one pectineal crest or eminence to another ; 

 tho mean of this is 8 ^ inches. The two last diameters are estimated from 

 the inferior face of the sacro-iliac articulation of one side to the ilio-pectinoal 

 eminence of the other ; this is on an average 8^ inches. These measurements 

 irrefutably demonstrate that the inlet is not elliptical in the vertical direction. 



The posterior aperture or outlet, situated at the posterior end of the pelvic 

 cavity, gives exit to the rectum and genital organs. As the pelvis of tho 

 horse is horizontal, the outlet should be considered as limited, we think, by 

 the inferior face of the summit of the sacrum, the superior face of the ischia, 

 the supercotyloid crest or ischiatic spine, and the internal face of tho 

 sacro-ischiatic ligaments. At the outlet only two diameters are recognised : 

 a vertical and a horizontal. The vertical measures on an average 6 r 7 ff inches ; 

 it extends from the inferior face of the sacrum to the superior face of tho 

 ischial symphysis. The horizontal diameter, comprised between the two 

 supercotyloid crests, is 7 T 7 ^ inches. 



Tho superior region of tho pelvic cavity is a little concave from before 

 to behind ; it has for base the sacrum, which presents on each side of tho 

 median lino tho subsacrul foramina. This part is also called the sacral 

 plane or roof of the pelvis. 



The inferior region, or ischio-pubic plane, is formed by the pubis and 

 the ischia. It is concave from side to side ; its anterior border is nearly 

 straight, and its posterior border is scooped out by a wide notch to form tho 

 arch of the iscliium. 



It has been remarked by M. Gobaux, that the portion of this piano corre- 

 sponding to tho pubis presents numerous varieties. Tho superior face of the 

 pubis may be convex in its anterior moiety and concave in its posterior ; or 

 it may bo concave before and convex behind, the concavity being separated 

 from the convexity by a transverse ridge. This ridge is sometimes represented 

 by a scries of small conical eminences ; at other times this upper face is 



