THE POSTERIOR LIMBS. 



97 



disposed as a smooth inclined plane, directed backwards and upwards, and 

 a kind of rim surmounts the anterior contour of the oval foramen. 



With regard to the lateral regions, they are formed by a small portion 

 of the inner face of the ilia, and in great part by the sacro- sciatic ligaments. 



2. DIFFERENCES IN THE PELVIS OF THE SEXES. The pelvis of the Mare 

 exceeds that of the Horse in all its dimensions, but the difference is most 

 marked in the transverse diameters. 



The anterior inlet forms a vast circumference when compared with that of 

 the male ; the pectineal crests are widely apart, and the distance separating the 

 anterior border of the pubis from the lower face of the sacrum is considerable. 



If the pelvis be viewed in its superior plane, it is found that in the 

 Mare the ischiatic notches are very deep ; that the internal border of the 

 ilium forms a regularly curved and very concave line ; and that the supracoty- 

 loid crests, or ischiatic spines, are widely separated from each other. It is 

 also noticed that the floor of the pelvis is wide, and that the bones com- 

 posing it tend towards the same horizontal plane. 



In the male, the ischiatic border is only represented by a very curved 

 line ; this line is composed of two almost straight portions, which join at 

 an obtuse angle at the origin of the neck of the ilium ; the supracotyloid 

 crests are relatively near each other, and bent towards the longitudinal axis ; 

 while the two moieties of the pelvic floor are directed very obliquely down- 

 wards and inwards. 



In the Mare, the ischial arch is larger than in the male, and forms a 

 regular curve uniting the two tuberosities of the same name. In the Horse, 

 the two ischiatic tuberosities are but little apart from each other, and the 

 ischial arch forms a somewhat acute angle whose borders are nearly straight. 



Lastly, when the pelvis is examined in its inferior plane, in addition to 

 the features already indicated in the ischiatic arch, it is found that in the 

 Mare the obturator foramina are large and nearly circular, while in the 

 Horse they are elliptical ; the cotyloid cavities are also further removed from 

 the ischio-pubic symphysis in the female than the male. 



The sacrum of the Mare has appeared to us, in some individuals, to be a 

 little more arched from before to behind than that of the Horse ; but this 

 character is not constant. 



The following figures relating to the capacity of the pelvis in the Mare 

 and Horse confirm what has just been enunciated. 



