_The Causes of Round Shoulders._—The general conditions are those that produce muscular or constitutional weakness, as rapid growth, overwork, the impure air of ill-ventilated rooms, acute illness, near-sightedness uncorrected by glasses, lack of proper exercise, and the wearing of clothing supported by suspenders bearing on the points of the shoulders, tending to pull them downward and forward, or even to produce a painful deformity of the scapula. It is the rule rather than the exception to find, with round shoulders, some inequality in the height. The right shoulder is apt to be the lower, owing to the carrying of burdens on the right arm. Habitual standing with the weight on the right leg contributes to a good many cases. Games in which the right arm is almost exclusively used is another cause. [Illustration: Fig. 29.—The spinal column (Church and Peterson). ] _The Causes of Spinal Curvature._—The spinal column forms the central support of the body, and, for grace and suppleness of motion, its thirty-four joints should be constantly exercised, as well as the muscles which hold it erect and support the head upon it, as well as attach the shoulders, hips, and legs more or less closely to it. In brief, all the muscles of the back need varied and regular exercise to maintain the erect position of the body, and from early childhood especial attention should be given to develop and strengthen this region of the body. The normal movements of the spinal column are flexion, extension, side bending, and torsion. Flexion and extension take place, for the most part, in the lumbar and cervical regions. Gould believes that astigmatism is a prominent factor in the causation of spinal curvature; the curvature is affected by the tilting of the head to one side in reading or writing. But a faulty postural habit is probably the most frequent cause both in standing and at the desk. When the weight is supported by the right leg, the left being used merely as a prop; there is a marked =C=-shaped curve produced, with a lowering of the right shoulder and prominence of the right hip. This position is assumed by school children for long periods of time, and there is a consequent overstretching of the ligaments of the spine and hip. These cases are generally accompanied by round shoulders and flat chest, protrusion of the abdomen, and rotation of the vertebræ. A muscle can be developed only by the active contraction and relaxation of its fibers. Continuous tension quickly tires and lowers its tone, so that exercises given for increasing muscular power should be comparatively quick and frequently repeated, while those that aim at the stretching of muscles and ligaments should be slow and long maintained.