1. Variations due to displacement of vertebrae that may resemble subluxation: Marked anterior displacement of the second on the third cervical vertebra, resembling a true subluxation, was observed in 19 per cent of the children studied who were one to seven year old. A similar finding was present less frequently between the third and fourth cervical vertebrae. Overriding of the atlas on the odontoid process, seen on lateral roentgenograms made with the neck in extension, and apparrent wedening of the space between these two structures, visible on flexion views, occurred in 20 per cent of the normal children between one and seven years of age. Both were suggestive of ligamentous injury.