158 



PELVIS. 



make such a change of position more evident 

 in the Ox than in other domestic animals. 



Fig. 97. 



Pelvis of the O.r, showing the ilio-ischial angle (c d e}. 



It is somewhat interesting, that, in most 

 animals with flat sacral bones, the axes of the 

 anterior and posterior pelvic openings, as well 

 as that of the tubular cavity, coincide in the 

 same straight line. In the Cow, however, and 

 in some other Ruminants, these axes form a 

 considerable angle one with the other, on ac- 

 count of the greater curve of the sacrum. 

 This will, doubtless, have considerable in- 

 fluence in producing the more laborious par- 

 turition of these animals, which usually re- 

 quires artificial assistance. 



In the Ox the planes of the acetabula are 

 inclined about 40 from the perpendicular. 

 The pelvis of the gigantic Irish deer also 

 presents markedly this arrangement. 



In the American elk, the pelvis is rather 

 elongated and narrow, being small and weak 

 in comparison with the rest of the skeleton. 

 There is the dorsal projection of iscliial 

 tuberosities; and the ischio-pubic symphysis 

 is long, and diverges slightly from the spine 

 posteriorly. 



In the Camel the sacro-vertebral angle is 

 well marked ; the sacrum is much curved, 

 and composed of four pieces. The ilia are 

 long, strong, and blade-like, with the anterior 

 spine prolonged downwards and the alas 

 convex anteriorly. The ischia are compa- 

 ratively very short and feeble, set at a larger 

 angle on the ilia, and present a feebly marked 

 spinal ridge, and a well-marked outward 

 projection at the tuberosities. The pubes 

 are broad and moderately long, with a better 

 marked ilio-pubic anlc (120) than in the 

 preceding, and the ischio-pubic symphysis 

 is long and divergent anteriorly from the spine, 

 as in the Ox, the centre being opposite the 

 last sacral bone. The foramen obturatorium 

 is small, and the anterior outlet large and 

 oval. The lumbo-Hiac angle is about 140, 

 and the lumbo-pubic is rather less than a right 

 angle. 



In the Giraffe the sacrum is narrow, and 

 its angle with the spine indistinct. The ilia 

 are not very long, and the crest, unlike most 

 Ruminants, is convex instead of concave, 

 the wings being expanded and concave in- 

 ternally. The ischin are long and curved 

 upwards, with everted and laterally flattened 



tuberosities. The pubes short and very thick, 

 with long symphysis, forming a thick tube- 

 rosity, and much diverging from spinal column 

 anteriorly. Ilio-pubic angle large, 140 ; 

 lumbo-iliac, 150. 



In Sheep and Goats the sacrum is broad, 

 and its angle indistinct. The ilia are long and 

 blade-like, with scanty wings; lumbo-Hiac angle, 

 H5. Ischia broad and short, with large later- 

 ally projecting tubt- rosities ; and a rudimentary 

 spine in the Ram. The pubes are longer than 

 in Deer, and directed horizontally inwards. 

 The pelvic outlets are large, as also are the 

 sacro-vertebral and ilio-ischial angles. 



A very distinctive pelvic peculiarity is seen 

 in the Mcminna, or Pigmy Chevrotain. The 

 ilia and ischia are, in this curious animal, 

 ankyloscd to the sacral vertebrae. The osseous 

 ridges in the site of the oblique posterior 

 ilio-sacral ligaments are very prominent, and 

 the ossified sacro-sciatic ligaments are distinct 

 and well marked. The sciatic notch is thus 

 converted into a foramen, and the pelvis re- 

 sembles in this respect that of the Sloth. In 

 the Musk Deer, also, the last sacral transverse 

 processes nearly abut on the short and clorsally 

 projecting ischia. In the heavier Ruminants, as 

 the Camel, gigantic Deer, and Ox, the pelvis 

 has somewhat of the heavy appearance and 

 overhanging acetabula of the Pachyderms, but 

 in the lighter Deer and Goats it becomes gra- 

 dually more slender and elegant in form, and 

 more oblique in direction. 



In the Rodentia, the pelvis is largely de- 

 veloped for the support of the powerful hinder 

 extremities in leaping, the most usual mode 

 of progression of the generality of these 

 animals. 



The sacrum is generally continued in a line 

 with the lumbar curve in the long-tailed 

 species. In Hares and Rabbits, however, the 

 sacrum is considerably arched, longitudinally 

 as well as transversely (fig. 98. a), and its 

 angle with the spine marked 160. There are 

 generally four sacral vertebrae, but the first is 

 much larger than the others, especially in its 

 lateral masses (b), to articulate with the ilia. 

 The Rabbit and Jerboa, however, present only 

 two; and the common Rat and Beaver three; 

 while the number in the Marmot is as many 

 as six. The spines are not coalesced except 

 in some Rats. The caudal vertebra? are more 

 or less numerous, and are remarkable in the 

 Beaver for the great length of the transverse 

 processes and anterior spines, for muscular 

 hold on this its useful appendage. In the 

 Squirrel and Jerboa also, the tail is long and 

 strong, and in the habitual sitting posture of 

 these animals it forms, with the ischia, the third 

 leg of a tripod, on which the body is sustained. 

 In the short-tailed Rodents, the caudal ver- 

 tebrae are curved clorsally, in an opposite di- 

 rection to the coccygeal bones in Man and the 

 Sin/ice. 



The ilia are long, prismatic, and slender in 

 the shaft, having a central ridge passing up- 

 wards from the cotyloid cavity, with a groove 

 on each side of it externally, and continued 

 forward into elongated alae, little more ex= 



