

94 SKELETON. 



Some years ago, I met with a case in which there was every 

 reason to believe that a partial displacement or dislocation had 

 occurred about the fourth vertebra, in a boy of eight or ten years. 

 It rose from his struggling to extricate himself from the grasp 

 of a school-mate, who held him near the ground by the back of 

 the head, with the spine bent forwards. This position, it is 

 evident, was calculated to lift the oblique processes of the verte- 

 brae over each other; and an oblique force applied at the same time 

 consummated the accident, by twirling the lower oblique process 

 over the upper margin, and in front of the one with which it 

 was articulated below. The displacement was manifested by 

 inability to move the neck; by a permanent inclination and turn 

 of the head to the side opposed to the injured one; and by an 

 inequality in the range of the anterior points of the transverse 

 processes of the side affected. I succeeded in replacing the bone 

 by lifting its dislocated side over the lower oblique process, 

 communicating at the same moment a rotatory motion, the re- 

 verse of that by which the accident had happened. In an in- 

 stant, the patient was relieved; from extreme pain, fixed defor- 

 mity, and inability to move the neck, he performed with freedom 

 all the motions natural to the part. 



The principal motions of the head upon the first vertebra are 

 those of flexion and extension: the power of the condyles to 

 slide horizontally from one side to the other in the cavities 

 formed in the atlas, is excessively restricted, both by the shape 

 of the proximate articular surfaces, and by the arrangement of 

 the ligaments: this motion is, in fact, so inconsiderable as scarce- 

 ly to deserve notice. Even flexion and extension appear greater 

 than they actually are, in consequence of the lower vertebrae 

 most commonly concurring in these motions. When simply 

 the head is flexed upon the atlas, while the other vertebrae are 

 kept erect, the chin approaches the sternum, and the skin of the 

 neck is thrown into folds; but when all the bones are flexed, 

 the head is thrown forwards and the skin is kept tense. The 

 flexion of the head upon the atlas is restricted by the ligamen- 

 tum nuchae, and by the ligament passing from the posterior 

 margin of the occipital foramen to the posterior bridge of the 

 atlas. The extension of the head is restricted by the vertical, 

 moderator, and anterior vertebral ligaments. 



The motion of the atlas upon the axis is limited strictly to 



