26 



OBSTETRICAL ANATOMY. 



and the distance between the lower face of the sacrum and the anterior 

 border of the pubis is much greater, the ilia and pubis being broader and 

 more concave. On the upper surface of the Mare's pelvis, the sacro-sciatic 

 notches are. very deep ; the inner border of the ilium forms a very concave 

 line, anc] the ischiatic spines are widely separated. The floor of the pelvis 

 is wide, and the bones composing it have a tendency to assume the same 

 horizontal direction. In the Horse, the ischiatic border does not describe 

 a regular curve ; it is composed of two nearly straight portions, which unite 

 where the neck of the ilium begins. The supra-cotyloid crests are not 

 much separated, and are turned outwards, and the two portions of the 

 floor of the canal are directed very obliquely downwards and inwards. In 

 the Mare, the ischial arch is wider than in the Horse, and forms a regular 

 curve in joining the tuber ischii ; while in the Horse, these tuberosities 

 are not nearly so wide apart, and the ischial arch forms a somewhat acute 

 angle, the margin of which is nearly straight. The obturator foramina 

 are also large and almost circular in the Mare, while they are small and 

 oval in the Horse ; the ischio-pubic symphysis is farther from the coty- 

 loid cavities in the former than in the latter. 



The sacrum is also broader and longer in the Mare, and in the majority 

 of animals it is more concave from before to behind. The first coccygeal 

 vertebrae are larger and more flexible, and carried at a greater elevation 

 than in the Horse. 



This difference of conformation in the pelvis of the Mare is adapted to 

 the passage of the foetus through the canal, and it causes the animal to 

 appear lower in the forehand than the Horse, in which the croup is not 

 so high. It is rare to find a Mare which has the croup so square as the 

 Stallion, the hind quarter of which is almost equal in depth, breadth, and 

 length. 



The width of the pelvis of the Mare, as before observed, produces a 

 rocking motion during progression, and this is all the more marked as the 

 animal has been frequently bred from ; for the same reason the speed is 

 not so great, and Mares which have had several foals are not well adapted 

 for the circus. 



The differences between the pelvis of the Mare and Horse are some- 

 times noticeable at birth ; but they are generally most apparent when the 

 adult period has been reached, and the body has acquired its definitive 

 form. In both sexes, the supero-inferior diameter of the inlet is greater 

 than the transverse in early life. 



Some idea of the difference in the dimensions of the pelvic cavity in 

 the Mare and Horse, may be obtained from the following measurements 

 of two animals about the same in size : 



The differences between the pelvis of the two sexes are, perhaps, not so 

 marked in the smaller domesticated animals until the female has brought 

 forth young several times. 



