3O Anatomy of Skeleton 



The dorsal region is naturally the most fixed portion of the true vertebral column, 

 and its bodies afford evidence of the nature of the dorsal curve in their slightly lesser 

 vertical depth in front : this agrees with the primary nature of the curve, and the 

 comparative immobility of the region is related to the shallowness of the intervertebral 

 discs. 



Observe that the upper facets on the tenth are largely on the free pedicles, and those of the 

 ninth to a lesser extent ; the facets on eleventh and twelfth are also largely on the pedicles, but do 

 not reach the upper margins at all. This simply indicates the reduction in size of the rib, with 

 consequent contraction, so to speak, of its area on the neural arch. It has been pointed out 

 already that the rib is purely neural in its articulation, and the line of the neuro-central synchon- 

 drosis, though not apparent in the adult bone, lies just in front of the facet on the body, so that the 

 facet is not on the centrum, but on the extreme front end of the neural portion. But while the 

 fully-developed rib extends its articulation to the limit of the arch that carries it, the reduced bone 

 withdraws from this extremity, and thus comes on to the pedicle. 



The thick pedicles are attached to the backs of the bodies high up, so that the 

 upper intervertebral notches are almost non-existent : in the first segment, however, 

 the prominence of the neuro-central region in front, as in the cervical series, makes the 

 notch well marked. In the case of the second vertebra the pedicles are placed so far up 

 that the plane of the upper surface of the body passes through them obliquely : it must 

 also be observed that the pedicles of the upper segments are directed slightly upwards 

 as well as backwards. 



The transverse processes are strong for the support of the ribs : in the last two 

 vertebrae, where the ribs do not articulate with the processes, they are much modified. 

 Their facets depend for their direction and appearance on the position of their ribs 

 in the series : thus the true or sternal ribs are the upper seven, the remainder being 

 " false " ribs, and the upper facets are well-marked, large, concave surfaces, situated 

 on the front aspects of the transverse processes and in a vertical plane, whereas the 

 facets for the lower ribs are smaller and flatter and tending to lie on the upper aspect 

 of the process and to look upwards. 



The seventh facet is usually a transition form in these characters, but occasionally, 

 when the eighth rib reaches the sternum, the eighth facet becomes transitional, and 

 the seventh has the characters of those higher up. The tenth facet is small and badly 

 marked, or may apparently even be absent. 



The differences in the facets may have to do more with the attachment of the diaphragm to the 

 false ribs than with any inherent result of their asternal position, but, however this may be, the 

 variations are sufficient in themselves to indicate that the direction and method of movement of 

 t he ribs differ in the upper and lower series ; but of the nature of the movements divergent opinions 

 are held by observers. 



On the first transverse process the facet is at its extremity, and may look almost 

 directly outwards : in some short processes it may even look outwards and backwards, 

 but this may be the result of disease. The process in the first D.V. is directed most 

 transversely, those below this showing increasing obliquity backwards. 



In the eleventh vertebra the process may be a mere shapeless mass, or it may 

 show an arrangement of tubercles on the same plan as in the last dorsal vertebra 

 (Fig. 25). 



In the twelfth vertebra there are three tubercles to be seen, the upper, lower, 

 and external, of which the first two at least are for muscular attachments : these will 



