In the Lumbar region rotation is the commonest form of subluxation, the axis of rotation being laterally movable upon a transverse line between the articular processes in the beginning and shifting, as soon as the vertebra leaves its normal relations, to the junction of the articular process with that of the adjacent vertebra on the side toward which the spinous process is moving. Thus, in rotation of the vertebra so that the spinous is to the right, the axis will be found on the right side, the superior articular process of the next vertebra serving as a support on which the inferior articular process of the rotating vertebra may turn. The processes are so firmly locked that unless the whole vertebra be quite posterior little lateral movement of the spinous process is possible without marked rotation. The body describes the greatest arc because it is further removed from the center of rotation than is the tip of the spinous. Tipping This is a subluxation in which the one transverse process is, or appears to be, superior or inferior to the other. It occurs frequently to the Atlas in combination with lateral subluxation. In fact, the shape of the occipito-atlantal articulations is such that, if the remaining Cervicals maintain their proper relation to each other, the Atlas cannot be laterally displaced without a certain amount of tipping. It will be relatively superior on the prominent side and the head will be tipped toward that side; that is toward the side of the lateral displacement. Thus, on account of the wedge-shaped lateral masses, if the whole Atlas be to the right of its normal position the right side will be superior and the head tipped toward the right. This is only true when the vertebrae below maintain a normal interrelation. Approximation This is a name applied to that condition in which, on account of changes in the intervertebral disks due to subluxation interfering with metabolic processes, the bodies or spinous processes of vertebrae are crowded too closely together. Occasionally a spine is found in which, on palpation, the spinous processes are found to be crowded together in groups, sometimes of two or three, sometimes of five or six; no two interspaces appear equal, a very wide one being succeeded by one or two which are almost inappreciable; the variation in width of the interspaces does not correspond to the known normal variation in those regions where the changing obliquity of spinous processes should modify the relative width of successive spaces. We expect, for instance, to find a wider space between third and fourth Dorsals than between second and third; if we do not find this difference it is doubtless due to cartilage change and the vertebrae are approximated.