- CERVICAL' VERTEBRJE. 145 



vertebra. The inferior oblique processes of this vertebra 

 answer exactly to the description given of those common to 

 all the cervical vertebrae. 



The transverse processes of the vertebra dentata are short, 

 very little hollowed at their upper part, and not forked at their 

 ends ; and the canals through which the vertebral arteries pass, 

 are reflected outwards about the middle of each process, so that 

 the course of these vessels may be directed towards the trans- 

 verse processes of the first vertebra. Had this curvature of the 

 arteries been made in a part so movable as the neck is, while 

 they were not defended by a bone and placed in the cavity of 

 that bone, scarce a motion could have been performed without 

 the utmost hazard of compression. This is the third instance, 

 of similar mechanism in cases of sudden curvature of arte- 

 ries. The first is the passage of the carotids through the 

 temporal bones ; and the second is that lately described, where 

 the vertebral arteries turn round the oblique processes of the 

 first vertebra, to come at the great hole of the occipital bone. 



The spinous process of this vertebra is thick, strong, and 

 short, to give sufficient origin to the musculi recti majores and 

 obliqui inferiores, and to prevent the contusion of the^se and 

 other muscles in pulling the head back. 



The four cervical vertebras which are next in order have 

 nothing particular in their structure, but agree with the general 

 description. The seventh vertebra approaches the form of those 

 of the back, having the upper and lower surfaces less excavated 

 than the others. The oblique processes are more perpendicular ; 

 and the spinous as well as transverse processes are without 

 bifurcation. 



After an examination of the condyles of the os occipitis, and 

 of the whole structure of the atlas and vertebra dentata, it will 

 be evident, that the flexion and extension of the head, or its 

 motion backwards and forwards, is effected by the movements 

 of the condyles of the occipital bone on the atlas ; and that in 

 the rotation of the head, the atlas revolves to a certain degree 

 round the processus dentatus of the second vertebra : the head 

 necessarily moving with it. 

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