PELVIS. 



153 



evident degeneracy of pelvic structure, allying 

 them much more closely to the quadrupeds, 

 especially to the Carnivora, than to mankind. 

 And we may remark, more especially, that their 

 fitness for the habitual erect position is much 

 diminished by the want of direct antero-pos- 

 terior extension of the pelvis, produced by the 

 flatness of the sacrum and the less marked 

 sacro-vertebral angle, and the shortness and 

 change of direction of the pubis; which renders 

 the arms of the pelvic lever shorter from the 

 cotyloid fulcrum, and the hold of the extensor 

 and flexor muscles of the thigh less powerful 

 in maintaining the standing posture. And, cor- 

 responding to this, we see in these animals, 

 great diminution in the bulk of these muscles, 

 particularly in the glutci and gastrocncmu, the 

 plumpness of which constitute the buttocks 

 and calves characteristic of the human figure 

 From this cause, the gait of these animals in 

 bipedal progression is very unsteady. 



The expanded, everted, and large ischial 

 tuberosities, and the strength of the ischio- 

 sacral arch, indicate that the sitting posture is 

 more natural to the Simial race ; while the 

 greater depth of the posterior than the supe- 

 rior part of the cotyloid brim shows, as well 

 as the marked ilio-pubic angle, a provision for 



give a square outline to the inferior outlet- 

 Ischial tuberosities not flattened. In the 

 Capuchin Monkey the ilia are parallel with 

 the spine, the ischia are inclined forwards to 

 the abdominal surface, and the pubes are 

 more oblique. In the Semnopithecus cutellus 

 the sacrum is more arched laterally and 

 broader. The ilia are prismatic and long, 

 and project more behind the spinal column. 

 The ischia and pubes are short, with flattened 

 and expanded tuberosities, and no ischial 

 spine. Ilio-pectineal eminence marked. In 

 these tribes the posterior border of the 

 elongated ilia is the thickest part of the bone, 

 the anterior part being thinned and spread 

 out more or less. The pubes are generally 

 placed nearly at right angles to the ilia, and 

 the lumbo-iliac angle is about 160. 



Of the genus Ccrcopithccus, or Baboon tribe, 

 there is, in the brown Baboon, a well marked 

 sacro-vertebral angle (155) ; the two upper 

 of the three sacral vertebrae only articulate 

 with the ilia. The caudal vertebras are not 

 numerous. The ilia are more expanded, but 

 still present the posterior concavity. The 

 ischia are short, with very broad and flattened 

 tuberosities. The pubes are flattened, with an 

 acute superior border, and rostrated at the 



femoral support in a semiflexed, rather than an symphysis. Ilio-pubic angle moremarked(^l 10). 

 extended position. In the erect posture, from 

 the flatness of the pelvis, the ischial tuberosi- 

 ties are brought close upon the femurs, and 

 reach nearly half-way clown their short shafts, 

 interfering much with their motion. 



According to Grant and Wagner, there is 

 no cotyloid notch nor ligamentum teres in the 

 Orangs ; but the cotyloid notch is present, 

 though small, in the skeletons I have examined. 



In the Hylobatis Lar, or long-armed Gibbon, 

 the iliac wings are flatter, and directed still 

 more antero-posteriorly, crest rounded, large, 

 and elevated ; ischui short, in a right line with 

 the ilia, with flattened and expanded tube- 

 rosities, spines more distinctly marked, and 

 rami directed, like the elongated pubes, more 

 directlyjnwards. The cotyloid cavities are 

 thus more widely separated, and the superior 

 pelvic outlet has a triangular form, with the 

 small end directed backwards. The sacrum is 

 narrow and flat, forming a large angle with the 

 spine, and composed of five vertebrae, of which 

 the three upper, considered by Blainville to 

 be the only true sacral vertebras, articulate 

 with the ilia. The coccyx, consisting, ac- 

 cording to Blainville, of seven, according to 

 others, of five vertebrae, is short, there being 

 no tail. The inferior outlet is large, and the 

 true pelvis shallow, from the shortness and 

 expansion of ischia. 



The subgenera Callithrix, Cercocebus, and 

 Semnopithecus present an elongation of the 

 coccyx into a caudal appendage with prehensile 

 attributes, and perforated for the continuation 

 of the spinal cord, which widens still more the 

 progressive separation from the human type. 

 In the Squirrel Monkey are three sacral 

 bones, of which the two upper articulate with 

 the ilia, and the broad transverse processes of 

 the last project towards the ischia, so as to 



In the Mandrill, Papio Marmon, the sacrum is 

 more arched both vertically and transversely, 

 and the promontory better marked. The 

 coccygeal vertebra? are four in number, and 

 there is no tail. The ilia are parallel with the 

 spine, directly under which are placed the co- 

 tyloid cavities. The ischia are short, with 

 much-expanded and flat tubers. The pubes 

 are at right angles, both to ilia and spine, and 

 the ischio-pubic symphysis is very little ad- 

 vanced before the plane of the spinal column. 



In the Sapajous, or American Monkeys, 

 there are three sacral vertebrae, of which the 

 first only articulates with the ilia in the 

 Onistiti. In the White-bellied Ateles the ilia 

 are longer and more expanded ; pubes more 

 oblique ; ischia short, with no spine, and small 

 tuberosities. In the Saimiri there is a very 

 short ilio-ischium. 



In the Lemurs, or Makis, the sacrum is in 

 a right line with the spine. Of the three 

 sacral vertebras, the first only articulates with 

 the ilia, and the last is not ossified to the 

 second. They differ little from the lumbar 

 vertebrae, except in the thicker transverse 

 processes. Caudal vertebrae numerous. The 

 pelvis generally is very weak, narrow, and 

 short. The ilia are narrow and almost pa- 

 rallel with the spine, and the ilio-pectineal 

 eminence is unusually well marked; but the 

 ischial tuberosities are delicate, indicating the 

 less frequent sitting posture in these animals, 

 and a still greater tendency to quadruped pro- 

 gression. In the Lemur albifrons, however, 

 the sacrum is broader ; ilia more expanded ; 

 ischial tuberosities larger and more expanded; 

 ilio-pubic angle 120. In L. tardigradus the 

 sacrum is long, narrow, and keeled in the 

 middle, being ankylosed to the last lumbar 

 and three first coccygcul vertebrae, as in birds. 



