normal side, cause a scoliosis similar to that due
to irregularity in the length of the lower extremities, and is
similarly made to disappear when the patient sits upon a flat surface.

_Malformation_ or _disease of the vertebrae_ themselves is a well
recognised cause of scoliosis; the best known, as it may be also the
most severe and the most intractable, is that due to rickets, under
which heading it has already been described (Fig. 225). In a few cases
a rudimentary wedge-shaped vertebra has been revealed by the X-rays.

[Illustration: FIG. 225.--Rickety Scoliosis in a child aet. 2.]

In all of these forms or types of scoliosis the primary cause must be
searched for and when found is made the first object of treatment; the
treatment of the scoliosis as such is on the same lines as in the
postural variety that now falls to be described.

#Habitual or Postural Scoliosis.#--These names have been given to the
type of scoliosis that develops in young girls and for which there is
no mechanical explanation.

It is most frequently met with in rapidly growing girls of poor
physique who are overworked at school or lessons, or on commencing an
apprenticeship for which they are physically unfit. In some cases
there is nasal obstruction from adenoids, in others the development
and free play of the chest are interfered with by tight and
ill-fitting garments; in all of them the muscular system is weak and
the muscles of the trunk do not take their proper share in maintaining
the erect posture. The most important determining factor would appear
to be the habitual or repeated assumption of faulty attitudes, partly
from carelessness, largely from fatigue, in order to relieve the
feeling of tiredness in the back. So far as is known, the condition
does not occur in communities living under aboriginal conditions. In
some cases there is a hereditary tendency to scoliosis; we have seen
it, for example, in a father and his daughters.

The excessive use of one arm in the carrying of weights, the habit of
resting on one leg more than the other, or the assumption of a faulty
attitude in writing or in playing the piano or violin, doubtless,
determine the seat and direction of the curvature, and, when it has
once commenced, tend to aggravate and to perpetuate it.

It is probable that the greater frequency of the primary curvature
towards the right is associated with the more general use of the right
hand and arm, although primary curvatu