b ANATOMY OF THE HORSE. 



of axis or vertebra dentata. — In Jigure, quadrangular. Body, 

 oblong ; anterior surface of it, smooth, convex, heart-shaped, 

 apex turned downwards ; posterior surface, correspondently 

 concave. The vertebral hole is larger than in the other classes, 

 and semi-oval in figure. Two spinous processes ; the crest or 

 superior one is bifid, cleft and divergent posteriorly, united at a 

 sharp angle anteriorly ; the inferior (the additional) spinous 

 process is curved like an S reversed and inclined .^,^ ; being con- 

 vex and prominent posteriorly, sharp-edged and curved upwards 

 anteriorly. The transverse processes are very broad, but short, 

 arise from the body as well as the arch, are bifid, presenting 

 four projecting ends, two forwards, two backwards, and are 

 each perforated by a foramen, which transmits the vertebral ar- 

 tery and vein. The articular processes are large, directed hori- 

 zontally forwards and backwards, and present broad surfaces 

 for articulation ; those on the anterior looking upwards and 

 inwards, those of the posterior downwards and outwards. The 

 notches are found between the articular processes and the body. 



DORSAL VERTEBRAE. 



Volume, less than that of either of the other classes. — Num- 

 ber, eighteen; (in some instances, nineteen;) distinguished by 

 their numerical order, counting from the neck backwards. 

 Body, small ; short, thick, and semi-circular ; flattened supe- 

 riorly, prominent and edged inferiorly ; anteriorly, smooth, con- 

 vex, and heart-shaped ; posteriorly, correspondently concave. 

 At the junction of the arch with the body are situated four 

 small cup-shaped articular surfaces, two presented forwards, two 

 backwards, which in conjunction with those next to them form 

 sockets for the reception of the heads of the ribs. The verte- 

 bral foramen is of less diameter than in the neck, and is oval 

 from side to side. Spinous process, long and flattened on its 

 sides ; thick and triangular or prismatic at its root ; presenting 

 a sharpened edge forwards, a flat or obtuse border backwards ; 

 thick, irregular, and tuberous at its summit. Transverse pro- 

 cesses, short and thick, incurvated upwards, and tuberous at 

 their extremities; their sides presenting circular articulatory 

 surfaces for the tubercles of the ribs. Articular processes, very 

 short and proceeding from the roof of the arch : the anterior, face 

 upwards ; the posterior, downwards and backwards. There are 

 only two notches, and these are smaller than those of the cer- 

 vical ; they are situated between the posterior articulatory pro- 

 cesses and the costal surfaces upon the body. 



