CHAPTER V. 



SPECIAL CHARACTERS OF THE THORACIC AND LUMBAR 



VERTEBRA 



IT will be most convenient to consider the vertebras of 

 these two regions together. 



In Man, there are seventeen trunk vertebree, 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 vertebra, 

 broad and depressed. They soon become more compressed, 

 especially at the lower part, so as to be sub-triangular when 

 seen from one end (Fig. 2, p. 16); 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 slightly 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 laminse 



are broad. The spines are moderately long, sub-equal 



E 2 



