THE VERTEBRM. 35 



two species ; then the processes become predominant in the Ass (Fig. 20, 

 A', B', 8, 3), and they preserve this character to the eighteenth. 3. All the 

 transverse processes are less oblique than those in the Horse ; also the line which 

 intersects, in the middle, the summit of these processes and their lateral articular 

 facet, passes always in front of the posterior facet on the body ; in the Horse, 

 this line traverses the latter facet, except in the lirst and fifth vertebra (Fig. 20, 

 A. B). 4. There are not seen on the nine last dorsal vertebrae of the Ass, the 

 anterior articular facets ascending to the base of the spinous process, as usually 

 occurs in the Horse. 5. Lastly, the notches of the intervertebral foramina are 

 nearly always closed by a bony bridge in the Ass, and only rarely so in the Horse. 

 The dorsal vertebrae in the Mule and Hinny offer the same mixture of 

 particular characters which are found in their parents ; though it is not doubtful 

 that the vertebrae of the Mule (Hinny) produced by the union of the female Ass 

 with the Stallion Horse, more resemble the former than the latter, especially 

 in the transverse processes. 



Differential Characters in the Dorsal Vertebra op other Animals. 



A. Ox. — In the Ox, these thirteen bones are longer and thicker than in the Horse. Their 

 spinous processes are larger and incline more backward ; their transverse processes are very 

 voluminous, and are provided with a convex facet from above to below ; while their posterior 

 notches are nearly always converted into foramina. 



Considered individually, they are more slender in the middle than at the extremities. Their 

 spinous processes diminish in width, especially at their summits, from the first to the eleventh 

 vertebra, and widen again in the two last ; they progressively increase in slope to the tenth, 

 after which they become more and more upright; tlie first four are the longest, and are nearly 

 the same in height : the others gradually decrease. 



In the first four or five vertebrae, the articular facet of the transverse processes, while 

 retaining its vertical convexity, is concave in an antero-posterior direction. This facet is 

 always absent in the last vertebra, and sometimes even in the preceding one. The two bones 

 terminating the dorsal region show, in addition, the articular processes disposed like those of 

 the lumbar vertebrae. 



B. Sheep and G-oat. — The thirteen dorsal vertebrae of the Sheep and Goat are relatively 

 less strong than those of the Ox; their spinous processes are not so wide, and their posterior 

 notches are never converted into foramina. 



C. Camel. — The dorsal vertebrae of the Camel, twelve in number, are remarkable for the 

 length of their bodies, and the height and width of their spinous processes. The transverse 

 processes are a little less detached than in the Ox, but they are very tuberous. The posterior 

 notclies are narrow, deep, and close to the base of the spinous processes; they do not form 

 foramina. The convexity or concavity of the articular surfaces of the body diminishes from the 

 first to the last bone ; while the spinous processes increase in length and width from the first 

 to the sixth, and diminish in the last six. These processes are much inclined from the third 

 to the ninth ; then they gradually become erect in the last three. 



D. Pig. — The Pig has fourteen dorsal vertebrae, which, in their general disposition, are 

 not unlike those of the Ox. As with that animal, the intervertebral foramina are double, each 

 vertebral lamina being perforated laterally by an opening situated in front of the posterior 

 notch. In addition, the vertebrae of the Pig present this peculiarity, that their transverse 

 processes are generally traversed at the base by a single or multiple foramen, which communicates 

 with the preceding. 



With regard to the special characters proper to some of the vertebras, these are, as with the 

 other animals, very few, and may be described as follows : 1. The transverse processes of the 

 four vertebrae preceding the last project but slightly. 2. In the fourteenth this process 

 resembles those of the lumbar vertebrae. 3. The articular facet of the transverse process in the 

 four last vertebrae is confounded with the anterior lateral facet corresponding to the head 

 of the rib. 4. The articular processes of the last five vertebrae are arranged like those of the 

 lumbar vertebrae ; and the prominence formed by the tubercle on the outside of the anterior 

 articular process replaces, to a certain degree, the transverse process of these vertebrae. 



E. Dog and Cat. — These animals have thirteen dorsal vertebrae formed on the same model 



