THE VERTEBRA. 



verteh-al bodies augments progressively from before to behind. Their lateral 

 diameter, which determines that of the spinal canal, becomes, on the contrary, 

 less from the first to the tenth vertebra ; after which it assumes increasing 

 proportions to the last one. The articular surfaces, which serve for the mutual 

 contact of head and cavity, become 

 larger and shallower in proportion 

 as the vertebra? are more posterior. 

 The inferior spine on the body is 

 very salient and tuberculated in the 

 two first vertebne, very acute in the 

 third and fourth ; it disappears in 

 the sixth and ninth, to reappear and 

 become more marked from the tenth 

 to the last. 2. The interrertpbral 

 cavities, intended for the reception 

 of the heads of the ribs, diminish 

 in depth and extent from the first to 

 the last. 3. The longest spinous pro- 

 cess belongs to the third, fourth, 

 and fifth vertebne ; those which 

 follow gradually decrease to the 

 eighteenth. Their width diminishes 

 from the second to the eighth ; it 

 afterwards increases in a progressive 

 manner in the succeeding vertebrae ; 

 from the second to the tenth vertebra, 

 the summit of the spinous process is 

 large and tuberculated ; in the last 

 seven it is flattened laterally. Their 

 obliquity is less marked as they pro- 

 ceed backwards ; in the sixteenth and 

 seventeenth vertebra?, the spinous 

 process is nearly vertical ; it inclines 

 slightly forward in the eighteenth. 

 Those of the tenth, eleventh, and 

 twelfth vertebrae are slightly curved 

 like an S. 4. The articular jrrocesses, 

 from the first to the tenth vertebra, 

 gradually contract and approach the 

 median line ; in the succeeding 

 vertebras they, on the contrary, 

 increase, and become concave and 

 wider apart from those of the oppo- 

 site side. 5. The volume of the transverse processes and the size of their diarthrodial 

 facets, diminish from before to behind. In the three first vertebra; this facet is 

 concave ; in the first nine the articular facet looks outwards and backwards, 

 while the facet on the body looks forwards ; in the last the two facets are 

 directed forwards. These two facets are generally confounded in the seventeenth 

 and eighteenth vertebrte. The first dorsal vertebra much resembles the 

 prominens ; it is distinguished from it, however, by the presence of four 



MIDDLE DORSAI, VERTEBRA OE THE HORSE, 

 VIEWED FROM THREE TYPICAL LINES. 



The first line, A B, passes frdin before to behind by 

 the most salient point of the transverse process, 

 intersecting the middle of the lateral facet in- 

 tended for the tuberosity of the rib, and of the 

 cavity on the border of the posterior articular 

 surface of the body. Below is the intervertebral 

 foramen, the spinous process, and the articular 

 facets on the base of the latter. The line C D 

 is tan(;ent to the summit of the transverse pro- 

 cess and head of the vertebra; it intersects the 

 anterior articular processes. The line M N is 

 horizontal, and tangent to the inferior face of 

 the body. 



