PELVIS. 



157 



are not united in a crest. The ilia approach 

 in shape to those of the Tapir, being in a less 

 marked degree T-shaped ; the posterior limb 

 of the iliac wings projecting inwards as far as 

 the sacral spines ; the anterior superior spine 

 often presenting an epiphysis, and the shaft 

 being long and blade-like. The ischia are 

 comparatively long, and much more slender 

 than in the Ruminants, being placed nearly 

 parallel with the coccygeal vertebra, and with 

 prolonged tuberosities. The pubes are small 

 and short, and directed a little forwards, as 

 well as downward and inward, with a marked 

 ilio-pectineal eminence, and a very long ischio- 

 pubic symphysis. The sciatic notch is wide, 

 and the obturator foramen small. The an- 

 terior outlet is large and squarish, and the 

 posterior elongated vertically and somewhat 

 diamond shaped. Lumbo-iKac angle rather 

 larger than that of the Tapir, being about 

 130 ; itio-isc/iial, 145; and the ilio-pubic about 

 130; making the lunibo-pubic rather less than 

 a right angle. 



In the Ruminantia the sacrum is composed 

 generally of four vertebras, the two upper 

 articulating with the ilia. In the Gazelle and 

 Antelope, however, there are five, and in the 

 common Stag only three. The sacrum is pro- 

 portionably broad, and more arched, both 

 longitudinally and laterally, than in the pre- 

 ceding orders. The sacral promontory is also 

 better marked, and the sacro-lumbar angle more 

 perceptible. In the Ox. especially, this reaches 

 to about 145 to 150, and in the Fallow-deer 

 160. The sacral spines are coalesced in a 

 perfect crest in the Ox, Fallow-deer, and Stag 

 (fig. 96. a), and partially in the gigantic Irish 

 deer, Gnu, and Equine antelope ; not so in 

 the Giraffe and Camel. The caudal vertebrae 

 are numerous. 



The ilia are long, with the crest (c) concave, 

 and the alae expanding laterally at the top, 

 especially in the heavier Ruminants ; being 

 concave internally, and convex externally, 

 and projecting much over the dorsal surface 

 of the spinal column, by the flattened and 

 elongated posterior superior spine (6). They 

 form little of the abdominal parietes, and 

 are placed on the spine at an angle of 

 HO to 150. The ischia are long and large, 

 and placed on the ilia at an angle (c d e) of 

 about 150 in the Deer and Sheep tribes, but 

 much less in the heavier animals. This in- 

 creased length and size of the ischia is parti- 

 cularly marked in the Deer tribe ; and, as 

 fulfilling the same mechanical requirements for 

 affording a long and strong hold for the power- 

 ful extensor group of pelvic muscles, allies them 

 with the Carnivora, and other springing 

 animals afterwards to be considered. 



The large and flattened tuberosities (e) 

 project much on the dorsal surface of the 

 pelvis. This is especially seen in the Fallow- 

 deer, common Stag, and Ox, with a well- 

 marked lateral tubercle (g), which is also pre- 

 sent in the Gazelle and Roebuck. They 

 present no ischial spine, except in the Lama, 

 where it is well marked. The pubes are very 

 short and slender, and are directed from with- 



out almost directly inwards, forming an Uio- 

 pubic angle of about 130 to 140. The 



Fig. 96. 



Pelvis of the Stag, lateral view. 



ilio-pectineal spine is much marked in Red 

 deer. Generally the ischia form part of the 

 elongated symphysis (/). 



In the Ox, the symphysis is not placed quite 

 parallel to the spine, as is usually the case in 

 the inferior animals ; but is placed obliquely ', 

 as in the human species, diverging more from 

 the spine at the anterior than at the posterior 

 extremity, and forming with it an angle of 

 about 20, and causing the anterior opening to 

 be larger than the posterior (see fig. 97. /). 

 The anterior opening is large and roundish, 

 with a prevalence of the antero-posterior 

 diameter. The posterior opening is more 

 square, but irregular and looking much up- 

 wards. 



The ischio-pubic portion of the pelvis is 

 altogether very long, and opposed to the coc- 

 cygeal vertebrae. In Deer, Goats, and Ru- 

 minants generally, but especially in the Ox, 

 the gradual upward curve of the ischia, and 

 the well-marked dorsal projection of their 

 tuberosities, cause them to appear promi- 

 nently on the rump, projecting on each side 

 and above the coccygeal vertebrae (figs. 96, 

 and 97. e.) In the Ox the Uio-ischial angle is as 

 much as 130; and the lumbo-iliac angle being 

 about 150, the acetabula are thereby placed 

 directly under the last bone of the sacrum, and 

 at the apex of an inverted arch (c d e) formed 

 by the ischium and ilium. By this elevation of 

 the ischia, the sacro-sciatic ligaments become 

 a means of support to the sacrum, as well as 

 the sacro-iliac, and thus that bone becomes 

 suspended between two curved springs, formed 

 by the ilio-ischion on each side. 



Thus in these animals the sacro-sciatic liga- 

 ments resist motion of the sacrum in a di- 

 rection downwards and forwards, a direction 

 totally contrary to those of the human pelvis, 

 as considered in the section relating to the 

 mechanism of that structure. And this change 

 of function, so simply transitionary, results 

 from the alteration of mechanical require- 

 ments in the quadrupedal position of the 

 trunk. About the period of parturition, the 

 sacrum of the Ox is said to sink evidently 

 between the ilia and ischial tuberosities, by 

 relaxation of these ligaments. The elevation 

 of the ischial tuberosities doubtless would 



