CHAPTER V. 



SPECIAL CHARACTERS OF THE THORACIC AND LUMBAR 

 VERTEBRA. 



It will be most convenient to consider the vertebrae of 

 these two regions together. 



In Man, there are seventeen trunk vertebrse, twelve 

 thoracic or rib-bearing, and five lumbar. 



The bodies increase in size from before backwards, and 

 also change their form. The first is like a cervical ver- 

 tebra, broad and depressed. They soon become more 

 compressed, especially at the lower part, so as to be subtri- 

 angular when seen from one end (Fig. 2, p. ijj ; after the 

 middle of the thoracic region they become more circular in 

 outline, and in the lumbar region they are wide transversely. 

 The ends of the bodies are flat or slighdy concave. 



The neural canal does not alter greatly in size throughout 

 this region, though it does somewhat in form. In the first 

 vertebra it is wider in proportion to its height than in any 

 of the others. 



The arches have comparatively narrow pedicles, arising 

 from the anterior half of the body, deeply notched behind, 

 for the canal for the exit of the spinal nerves. The laminae 

 are broad. The spines are moderately long, subequal 

 throughout the series, rather slender, and sloping backwards 



