OSTEOLOGY AND ARTHROLOGY ii 



those which cannot assume that attitude ; for example, the 

 sacrum of the ape, of the bear, of the dog, and of the opossum 

 are proportionately larger than those of the horse.* 



Its superior surface presents a crest, formed by the fusion 

 of the spinous processes of the vertebrae which form it. In 

 certain species these processes are attached only by their 

 bases, and are separated from each other superiorly. In 

 the pig they are wholly wanting. 



The Coccygeal Vertebrae. — These vertebne, few in 

 number (and sometimes ankylosed) in the human being, 

 form in the latter a small series, the coccyx ; which is in- 

 clined forwards, that is to say, towards the interior of the 

 pelvis. In quadrupeds, on the contrary, their number is 

 large ; they are not ankylosed, and they form the skeleton 

 of the caudal appendix. 



The first coccygeal vertebne — that is, those which are next 

 the sacrum — present characters which are common to those 

 of other regions : they have a body, a foramen, and pro- 

 cesses. As we trace them backwards, these characters be- 

 come gradually effaced ; and they become little more than 

 small osseous cylinders simply expanded at their extremities. 



Direction and Form of the Spinal Column 



The curves of the vertebral column are, in quadrupeds, 

 slightly different from those which characterize the human 

 spine. First, instead of their being, as in the latter, curves 

 in the antero-posterior aspect, because of the general attitude 

 of the body, they are turned in the supero-inferior direction. 



The cervical region is not a single curve, as in the human 

 being. It presents two : one superior, with its convexity 

 looking upwards ; the other inferior, the convexity of which 

 is turned downwards. This arrangement reminds one of 

 that of a console. 



* This is particularly striking only in those portions of the sacrum that 

 are not in relation with the other bones of the pelvis. We think that 

 the general form of this bone depends on the mode of its connexions with 

 the iliac bones and the extent of the articular surfaces by which it is in 

 contact with the latter. 



