DORSAL VERTEBRAE. 29 



ia form, each presenting a middle ridge along its under surface, 

 to which the inferior common ligament is attached. The superior 

 surface of the body, which forms the floor of the spinal canal, is 

 flattened and quadrilateral, presenting longitudinal furrows for 

 the spinal vessels, and often a central transverse one, partially 

 covered by a "bony plate. The anterior extremity presents a 

 slightly convex head, on the superior and lateral aspect of which 

 is a semicircular depression corresponding with another on the 

 posterior extremity uf the vertebra in front, so that together they 

 form a cup-shaped cavity for the articulation of a rib, each articu- 

 lating with one-half of the head of the rib. The posterior 

 extremity is concave, to articulate with the contiguous bone, and 

 has on each side an articular depression similar to those on the 

 anterior extremity. The transverse processes, rising from the 

 sides of the arches, are small ; superiorly and anteriorly they are 

 roughened for muscular attachment, and at its posterior inferior 

 part, each presents a flat, smooth facet which articulates with 

 the tubercle of the next anterior rib. 



The neural spines, larger than in any other region, vary much 

 in size, shape, • and direction, the first twelve being directed 

 backwards, the next three nearly upright, and the last tLree 

 forwards ; their length gradually increases to the fifth, which is 

 usually the longest, and then decreases to the fourteenth, which 

 is generally somewhat shorter than those behind it ; the first is 

 small and sharp, and the second, which is abruptly bent back- 

 wards, is -^ery strong ; the summits of the next six or seven are 

 flattened, roughened, and expanded laterally, assuming a bifid 

 appearance, giving greater surface for the attachment of muscles 

 and the great suspensory ligament of the head and neck, the 

 ligamentum nwchce. The lateral surfaces are convex and 

 slightly roughened, the anterior borders being thin and serrated, 

 while the posterior, of the higher spines especially, are broad and 

 concave, becoming cleft as they approach the oblique processes. 



The oblique processes are small, and their facets are more 

 horizontal than in the cervical region, and closer together. The 

 pedicles are short and strong, and, with the exception of the 

 anterior four or five, possess notches on their posterior edges 

 only ; backwards, we find these notches become more and more 

 closed in, until posteriorly there are foramina in lieu of notches. 

 The arch, and consequently the spinal canal, are small, the 

 laminae passing almost directly inwards from the pedicles. 



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