30 TEE BONES. 



In the fourth, the articular processes are united by a thin, sharp osseous plate, 

 notched only in front. Laid on a horizontal plane, the head remains some 

 distance from that plane. The fifth is recognized by the continuous, thick, and 

 rugged lamina which unites the articular processes, and by the tubercle of the 

 inferior spine on the body, which is in shape like the heart on a playing-card. 



Sixth.— T\n& is distinguished by the slight prominence of the spinous process, 

 but particularly by the almost total disappearance of the inferior spine, and the 

 presence of a third prolongation, very strong and inchning downwards at its 

 transverse process — a circumstance to which this vertebra owes its designation of 

 tricuspid. 



Seventh. — This has received the name of prominens, because its spinous pro- 

 cess, terminating in a point, is more distinct than in the preceding vertebrae, the 

 axis excepted. It exhibits, besides : deep imprints, which replace the inferior 

 spine ; a concave demi-facet on each side of the posterior cavity of the articulation, 

 of the head of the first rib ; a particular disposition of its transverse processes, 

 which are unituberculous ; the complete absence of the vertebral foramen ; and, 

 lastly, the depth and width of its notches. The spinal foramen, which has 

 already assumed a somewhat considerable diameter in the sixth cervical vertebra, 

 is still larger in the seventh. 



Ass. — The cervical vertebra3 in this animal much resemble those in the 

 Horse. Studying them more closely, however, it is possible to discover certain 

 differences which distinguish them from those of the other Equidfe. Thus, the 

 rugosities on the arch of the atlas are much less marked than in the Horse, and 

 form a kind of thick depressed tubercle. The vertebral foramen is very large 

 in proportion to the size of the vertebra, and the canal uniting the two portions 

 of the anterior foramen of the transverse process is deep and protected by a 

 well-defined rim. The axis has a less elevated spinous process than that of the 

 Horse ; its upper border, nearly parallel with the transverse process, is more 

 deeply divided into two lips, and the summit of its transverse process extends, 

 backwards to the articular process, while in the Horse it does not go beyond the 

 origin of the latter. In the third, the lamina uniting the two prolongations or 

 points of the transverse processes, is notched behind the anterior prolongation, 

 instead of being notchless as in the Horse. In the fourth Siud fifth this notch is 

 still more marke4. In every instance the anterior prolongation of the transverse 

 process is always more detached and better circumscribed in the Ass than in the 

 Horse. The same remark applies to the tricuspid ; the posterior prolongation is 

 also better detached, and the middle prolongation extends nearly to the articular 

 cavity of the vertebra — a prolongation which, in the Horse, does not exceed one- 

 half the length of the posterior one. The seventh differs little from that of the 

 Horse ; nevertheless, the uni-tubercular transverse process has, in front, a small 

 sharp projection which resembles somewhat the anterior prolongation of the 

 bicuspid processes. 



In the Mule and Hinny, the cervical vertebrae hold the middle place between 

 those of the Ass and the Horse. 



Differential Characters of the Cervical Vertebra in the other Domesticated 



Animals. 



A. Ox, Sheep, and Goat. — The cervical vertebrae of these animals differ from those of 

 Solipeds by their shortness, and the greater development of their insertion eminences. In the 

 Sheep and Goat they are relatively longer than in the Ox. The transverse processes of the 



