THE VERTEBRAE. 41 



they are bordered at their base and on each side by a ridge that represents the rudiments of the 

 articular processes. The lateral borders are sharp and bent downwards. The surfaces that 

 serve to unite the sacrum to the ossa innominata have a somewhat vertical direction. There 

 are no lateral facets on the base of the bone, for the union of the sacrum with the transverse 

 processes of the last lumbar vertebra. 



B. Sheep and Goat. — In the Sheep and Goat, the sacrum is shorter ; sometimes the con- 

 solidation of the spinous processes is late, or never occurs. 



C. Camel. — Sacrum short ancl composed of four vertebrae; broad and curved on its inferior 

 face. The spinous processes, rather low, are strong and free throughout their extent. The 

 auricular facets are cut very obliquely. 



D. Pig. — This is formed by four vertebrae, which are a long time in becoming fused 

 together ; and it is often difficult to discover where the sacrum ends and the coccyx begins.' 

 The spinous processes are entirely absent. The vertebral laminae are not consolidated ; so that 

 the spinal canal is half cut through in its upper portion, as in the cervical region ; this canal is 

 also much compressed above and below. 



E. Dog and Cat. — The three vertebrae which form the sacrum of Carnivora are early con- 

 solidated. The sacral spine constitutes a thin sharp ridge, while the lateral surfaces for 

 articulation with the ossa innominata are turned quite outwards, and are nearly vertical. 



F. Rabbit. — Relatively longer than tliat of Carnivora, the sacrum of this animal is remark- 

 able for the presence of four vertebrae, the spinous processes of which are isolated from each 

 other. 



5. Coccygeal Vertebe^. 



The coccygeal region, or coccyx, comprises from fifteen to eighteen degenerate 

 vertebrae, which gradually diminish in thickness from the first to the last. In the 

 first three or four, nearly all the characteristics of true vertebrae are found ; they 

 show a vertebral foramen, a body, a spinous process, and transverse processes, 

 directed backwards ; the articular processes only are altogether absent. In the 

 succeeding vertebrae, these characters become effaced ; the vertebral laminte do not 

 join completely, and the vertebral canal is only a simple groove, which, gradually 

 decreasing in depth, at last entirely disappears. The insertion eminences also 

 become less salient, and the coccygeal vertebrae are soon reduced to small bony 

 cylinders, narrow in the middle and wider at both extremities, with a convex 

 articular surface at each end (except the last, which has only one articular surface). 

 These small cylinders — the last traces of the vertebral bodies — are each developed 

 from three centres of ossification ; they are very spongy and light. The first 

 coccygeal vertebra is frequently consolidated with the sacrum in aged animals. 



Differential Characters of the Coccygeal Bones in other Animals. 



A. Ox, Sheep, and Goat. — In proportion, the coccygeal vertebrae of ruminants are stronger 

 and more tuberous than those of the Horse. The anterior articular processes exist in a rudi- 

 mentary condition. 



B. Camel. — Fifteen to eighteen in number, they are not so strong and are less tuberous 

 than in the Ox. The first six are channeled by a triangular canal. 



C. Pig. — These vertebrae in tlie Pig are more particularly distinguished by the presence of 

 articular processes, by means of which the foremost bones correspond with each other. 



D. Dog and Cat. — In these animals, the vertebrae of the coccyx are very strong and 

 tuberous. The first five or six are as perfect as the true vertebrae, and comport themselves in 

 every respect like them. The last are small V-shaped bones, which M. Goubaux has described 

 by the name of hypMoid bones. 



E. Rabbit. — The coccyx of the Rabbit is analogous to that of the Cat. 



' This can always be made out, however, by consulting the disposition of the articular pro- 

 cesses. Thus, in the sacral vertebrae these eminences — if we except the anterior ones of the 

 first and the posterior of the last — never exist except in a rudimentary state ; while in the other 

 five coccygeal vertebrae they reappear with all their characters. 



