Case III. Angular Curvature (Kyphosis), produced by the twelfth dorsal Vertebra consisting of two divided lateral halves. - The spine of a woman, aet. 55. The two portions form triangular rudiments inserted laterally between the eleventh dorsal and first lumbar vertebrae, with their points directed inwards: and they are united with the first lumbar in such a manner, that its body is very high at the sides, whilst in the middle it seems low, and is in contact with the eleventh dorsal. In consequence of this deficiency in the mesial line, the vertebral column is bent backward at a very obtuse angle. The arch of the divided twelfth dorsal vertebra is completely united into one piece with that of the first lumbar; but the half spines of the latter are so twisted, that the right one appears to be higher than the left. The last right rib is connected, by two heads, with the twelfth dorsal vertebra.

The curvatures which are acquired may be divided, as they are naturally, into the three cardinal forms: of curvature to either side, lateral curvature - scoliosis; curvature backwards, or angular curvature, the hump - kyphosis; and curvature forwards, sinking of the back - lordosis. Scoliosis, as will be seen in the sequel, may be combined with the other two curvatures. Moreover, it is of importance to distinguish the primary deviation from those which are consequent upon it, and compensatory.

a. Scoliosis is by far the most frequent of the three. There is sometimes only one curve: but more commonly a second, a compensatory inclination towards the opposite side at some other portion of the spine, renders the deviation sigmoid: in some cases there are several curves, and in others the scoliosis is combined with obliquity of the pelvis. When the lateral curvature is double or sigmoid, it is usually the dorsal region and the lumbar that are bent; and though the primary curvature may be in either region, it is far more frequently in the dorsal than in the lumbar. And further, the deviation in the dorsal region inclines most frequently towards the right side; whilst the compensatory curvature in the lumbar region to the left is itself compensated by a corresponding obliquity of the pelvis. In order to make even the little that has been said intelligible, as well as the statements which follow, it is necessary to point out the chief causes of scoliosis.

Attention has already been directed to the deviation of the spine which results from original inequality in the lateral halves of the vertebral skeleton. It is that to which Guérin attributes those cases of hereditary scoliosis which become perceptible between the ages of 7 and 10 years, and are generally unaccompanied by any trace of a rickety constitution. There is also a curvature to which the female sex is liable, in which Guérin ascertained that a disproportionate growth or elongation of the vertebral column, takes place at the period of puberty. But lateral curvature of the spine may come on at various periods of life subsequent to birth, under other conditions, which are as follow: