THE VERTEBRAL COLUMN. 31 



transverse process, and on the other, ou its posterior margin, after pursuing a certain 

 track in the substance of the bone. 



The odontoid process of the axis is constricted at its base. This vertebra is distin- 

 guished by its high and thin spinous process inclining slightly back, by its transverse 

 processes beiug but slightly prominent and perforated by an enormous vertebral 

 Ibramen. 



In the four succeeding vertebrae, the spinous process terminates in a blunt point, and 

 inclines forward; slightly salient in the tirst, it gradually rises in the others. The trans- 

 verse processes form two prolongations : one, the superior, is tuberculous, and is joined 

 to the anterior articular process by a plate of bone, which is pierced by a foramen ; the 

 other, the inferior, flattened on both sides, bent downwards, and large, as it belongs to 

 the posterior vertebrae, transforms the interior face of these vertebral bodies into a large 

 groove. The seventh is provided with a spinous process as long as those of the dorsal 

 region. A perforated bony plate, as in the preceding vertebrae, unites the anterior 

 articular process to the single tubercle composing the transverse process ; the latter is 

 continued back nearly to the pusterior notch by a second plate, also perforated with a 

 foramen (see Fig. 2). 



2. Dorsal vertebras. The Pig has fourteen dorsal vertebrae, which, in their general 

 dispositions are not unlike those of the Ox. As with that animal, the intervertebral fora- 

 mina 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 pecu- 

 liarity, 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 vertebrae, these are, as with 

 the other animals, very few, and may be described as follows ; 1. The transverse pro- 

 cesses 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 trans- 

 verse 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. 



3. Lumbar vertebrae. These bones in the Pig greatly resemble those of ruminant 

 animals. It commonly happens that seven are met with ; but in this case the supple- 

 mentary vertebra is generally a sacral one. It is not denied, however, that seven lumbar 

 vertebrae may exist in the Pig, along with the normal number of sacral vertebrae. 



4. Sacrum. 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. 1 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. 



5. Coccygeal vertebrze. These vertebrae in the Pig are more particularly distin- 

 guished by the presence of articular processes, by means of which the foremost bones 

 correspond with each other. 



C. VEKTEBR^E OF THE DOG AND CAT. 1. Cervical Vertebrae. In these animals, the 

 cervical vertebrae are long and thick, and much resemble those of solipeds. Nevertheless, 

 besides their smaller volume, they are distinguished : 1, By the disposition of their 

 corresponding articular surfaces ; ihe anterior, or head, is nearly flat, and is even slightly 

 excavated in its centre ; the posterior, or cavity, is but little hollowt d to receive the head 

 of the next vertebra ; 2, By the width of the vertebral laminae, which exactly cover one 

 another ; 3, By the height of their spinous processes, which increases as the vertebrae 

 extend back ; 4, By the great extent of the anterior and posterior articular processes, 

 which are united by means of a continuous and very salient bony plate, that considerably 

 augments the transversal diameter of each vertebra. 



In the atlas, the articular surface for the odontoid pivot is confounded in front with the 

 cavities which correspond to the occipital condyles. The two facets which 'are annexed 

 posteriorly to this articular surface, instead of being plane or gently undulated, as in the 



1 This can always be made out, however, by consulting the disposition of the 

 articular processes. 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 rudi- 

 mentary state; while in the other five coccygeal vertebrae they re-appear with all their 

 characters. 



