DORSAL VEKTEBRJE. 147 



of the other vertebrae; and a larger share of the holes in the 

 Fig. 35.* bony bridges for the transmission 



of the nerves, is formed in the 

 vertebra above than in the one 

 below. 



The connexion of the dorsal 

 vertebrae to the ribs, the thinness 

 of their cartilages, the erect situa- 

 tion of the oblique processes, the 

 length, sloping, and connexion of 

 the spinous processes, all contribu- 

 ting to restrain these vertebrae from 



much motion, which might disturb the actions of the heart and 

 lungs ; and in consequence of the little motion allowed here, the 

 intervertebral cartilages sooner shrivel, by becoming more solid ; 

 and therefore the first remarkable curvature of the spine 

 observed, as people advance to old age, is in the least stretched 

 vertebrae of the back ; or old people first become round-shoul- 

 dered. 



The bodies of the four uppermost dorsal vertebrae deviate 

 from the rule, that the vertebrae become larger as they descend ; 

 for the first of the four is the largest, and the other three below 

 gradually become smaller, to allow the trachea and large ves- 

 sels to divide at smaller angles. 



The two uppermost vertebras of the back, instead of being 

 very prominent forwards, are flattened by the action of the 

 musculi longi colli and recti majores. 



The proportional size of the two little depressions in the 

 body of each vertebra for receiving the heads of the ribs seems 

 to vary in the following manner : the depression on the upper 

 edge of each vertebra decreases as far down as the fourth, and, 

 after that, increases. 



* A lateral view of a dorsal vertebra. 1. The body. 2. 2. Articular facets 

 for the head of the ribs. 3. The pedicle. 4. The superior intervertebral notch. 

 5. The inferior intervertebral notch. 6. The spinous process. 7. The extremity 

 of the transverse process marked by an articular surface for the tubercle of the 

 rib. 8. The two superior oblique processes looking backwards. 9. The two 

 inferior oblique processes looking forwards. 



