We find that this process overlaps less and less the neighbouring vertebræ when we examine in succession the bear, the cat, the dog, the ox, and the horse. With regard to the other vertebræ of this region, they diminish in width from the second to the seventh; and, in some animals, the anterior surface of the body presents a tubercle which articulates with a cavity hollowed in the posterior surface of that of the vertebra before it; this feature dwindles away in the dorsal and lumbar regions.
The spinous process, slightly developed in the third cervical vertebra, gradually increases in size to the seventh, the spinous process of which, long and pointed, well deserves the name of _the prominent_ which is bestowed on it; but it should not be forgotten that the spinous process of the axis is equally developed.
[Illustration: FIG. 3.--SIZE OF THE ATLAS COMPARED WITH THE TRANSVERSE DIMENSIONS OF THE CORRESPONDING REGIONS OF THE SKULL IN A DOG.
1, Atlas; 2, zygomatic arch; 3, external occipital protuberance; 4, inferior maxilla.]
On the inferior surface of the body of each of the vertebræ is found a prominent crest, especially well marked at the posterior part; this crest is but slightly developed in the bear and in the cat tribe, and is not found in swine.
The transverse processes of the cervical vertebræ, from their relation to the trachea, are known as the _tracheal processes_.
The most marked characteristic of the dorsal vertebræ is furnished by the spinous processes. They are long and narrow. As a rule, the spinous processes of the foremost dorsal vertebræ are the most developed and are directed obliquely upwards and backwards. As we approach the last vertebræ of this region, the processes become shorter and tend to become vertical, and the last ones are even, in some cases, directed upwards and forwards; this disposition is well marked in the dog and the cat. In the cetaceans, on the contrary, the length of the spinous processes increases from the first to the last.
[Illustration: FIG. 4.--LUMBAR VERTEBRÆ OF A QUADRUPED (THE HORSE): SUPERIOR SURFACE.
1, Spinous process; 2, anterior articular process and transverse process of the first lumbar vertebra of the left side; 3, costiform process.]