The most extreme deformity presented by the thorax is that which occurs in lateral curvature, and in the combination of lateral with angular projection. It seems displaced in the opposite direction to the convexity of the dorsal curve, and the whole, or more commonly the lower end only, of the sternum, swerves from the mesial line in the same direction; the axis of the thorax itself inclines towards the convex side of the dorsal curve. One consequence of this deviation is, that that half of the thorax which is on the convex side of the curve is lower than the other, and approaches the pelvis; when there is considerable curvature, the false ribs touch the ilium, or even project into the iliac fossa. But in extreme cases of combined lateral and posterior curvature (scoliosis kyphotica) in the lower dorsal region, the thorax assumes the contrary position; the ribs which pass from the concavity of the curve force the chest to the opposite - the convex side; the sternum diverges in the same direction, and the sunken half of the thorax is that on the concave side of the curve.

Moreover, both sides of the thorax are flattened; and the amount of flattening is proportioned to the extent to which the vertebrae are twisted on their axes, and consequently to the size of the hump: but it is always most marked on that side of the chest which corresponds to the concavity in the spinal curve, and which may even be indented, while the other side is somewhat vaulted. The ribs take a more direct course outwards and forwards in proportion as they emerge from the deeper part of the concavity. They lie closer together, too, on that side, and may even be anchylosed at their posterior extremities; while those on the other side, especially about their tubercles, describe an arch which, when the vertebrae are very much rotated, encircles the bodies of those bones. Moreover, they lie further apart; in fact, their posterior extremities are separated from each other in exact proportion to the amount of the axial torsion of the vertebrae. Hence arises this difference between the two halves of the thorax: that on the concave side of the spinal curve is narrower from before backward, but has greater capacity laterally, while on the side of the convexity it has the converse dimensions; and again, the perpendicular measurement is shortened on the former side, and lengthened on the latter.

The condition of the shafts of the several ribs accords with these facts, more particularly with that which has been last mentioned. On the side of the concavity they are rounded, or rounded and angular; on the side of the convexity they are unusually flattened and ribbon-like: but however likely it might seem from the appearance of the ribs, yet no difference can be detected by the most careful measurement in the length of the several ribs and cartilages of the two sides.

In angular curvature the chest has a different character, - that is, as I have already remarked, in angular curvature in the lower dorsal and upper lumbar regions. In the first place it is thrown upwards; the anterior extremities of the upper ribs rise considerably higher than the posterior, so that the upper, and still more the lower, ribs form an arch which is convex upwards. The consequence of this elevation of the chest" is, that its perpendicular diameter is curtailed, whilst from before backward its dimensions are increased. The sternum preserves its relations to the bent column in the mesial line, but is thrown forwards; and as a consequence of the elevation of the anterior extremities of the ribs and of their arch-like vaulted form, it is thrown more forward the more it is depressed. The sides of the chest vary in shape according to the situation of the projection, and the acuteness of its angle. When it is in the lumbar region and moderately acute (94°), the ribs take a considerable lateral curve, and the chest is barrel-shaped; but if a projection in the same situation should form a more acute angle (60° for instance), and the column above, which includes the dorsal region, should be thrown much backwards; or if the projection should occupy the lower part of the dorsal region itself, the wrong direction of that part of the column in which the dorsal region is included, "whether it be one leg of the angle or both, will give a different form to the sides of the chest: for those ribs which pass from the angular projection of the column will run a straighter course than the others, in order to reach the projecting sternum, and the sides of the thorax at that part will be flattened; while above the angle the chest will be vaulted in the way first mentioned. Should the angle be extremely acute (55°), the sternum will bend backwards at its lower end, and become slightly arched, as if its greater depression removed it too far for the ribs to reach it, even by their new and more direct course.

The thorax, in every instance, approaches very close to the pelvis, and may even rest upon it: the abdomen, therefore, is much shortened.

This, however, is a rule which the thorax does not follow in a very acute angular projection in the upper dorsal region, or when the curvature is situated low in the loins. For in a specimen of the former description, in which the nine upper dorsal vertebrae were destroyed, I found the ribs closely packed together at their posterior extremities, but considerably depressed and straightened anteriorly; so that the thorax was flattened laterally, its axis much inclined, and the sternum thrown forwards. The compensatory curvature of the column forward was so great that, in spite of the depression of the thorax, the distance between it and the pelvis was nearly natural. In an example of the latter kind, the thorax was elevated; but the very great amount of curvature forward in the remainder of the lumbar, and the whole of the dorsal regions, and the pendulous protrusion of the abdomen (compare the state of the thorax in curvature forward) contracted the perpendicular diameter of the chest, while the considerable vaulting of its walls laterally, enlarged its transverse dimensions. (Compare the remarks upon this case below in reference to the pelvis).

In those cases of angular curvature in which the vertebrae are destroyed to a greater extent on one side than on the other, and in which, besides that the bones approximate on that side, it also happens, that the column above the angle is rotated on the axis of the vertebrae towards that side, and that the hump projects in the opposite direction; the thorax inclines towards the side on which the vertebrae are most destroyed, and sinks deeper on that side towards, and even into, the cavity of the false pelvis; while the sternum is depressed towards the same side as the hump; a compound, in fact, of lateral and angular curvature - scoliosis and kyphosis - produced by carious loss of substance, which may be named kyphosis scoliotica.

The state of the thorax is different again in curvature of the lumbar region forward, and in the excessive inclination of the pelvis backward, with which the lumbar curve coexists, and to which it is due. The chest is increased in length, and while the breadth of its lower part is strikingly greater than natural, it is very pointed above, and flattened from before backward. This remarkable form, especially the increase in length, is probably due to the abdominal muscles being stretched by the excessive inclination of the pelvis.