When there is no interference with the respiratory movements the uterus rises and falls with every breath, and the movements of the uterus promote the circulation of the blood in the pelvis. A high corset compresses the breasts, and so interferes with their development. The low corsets of the present day support rather than compress the breasts. _The Effects of Corsets on the Muscles._—In the back the corset forms an extended plane from top to bottom, destined to support the posterior part of the thorax and to diminish as much as possible the size and projection of the shoulder-blades. This compression of the muscles of the back leads to their atrophy, and, as it is their function to hold the spinal column erect and to approximate the shoulder-blades to the thorax, when they become atrophied the bony parts become much more salient. Further, the corset, in weakening the muscles of the dorsal region, interferes with the normal forward projection of the chest, and so leads to its flatness. The corset atrophies the articulations of the vertebral column, produces a round back, an inequality in the height of the hips and shoulders, with the resulting familiar awkward, waddling gait. When the healthy skeleton offers to the muscles of the body a solid base of support, the action of the muscles of the back are not interfered with, there is nothing to prevent their contraction, and the body is held erect. With a perfect muscular development, the shoulders are effaced, the back is admirably straight, and the carriage is erect and graceful. The strong compression of the muscles of the abdomen not only destroys the normal contour of the body, but, by the atrophy of the abdominal muscles, a partial paralysis is caused, and so the support which should be afforded the viscera by these muscles is weakened, and a prolapsus of the abdominal contents follows. It will be seen that the two bony cavities of the body are connected in the back by means of the vertebral column and are not immovably fixed in relation to each other, but by reason of the flexibility of the spinal column, they can be approximated or the distance extended. The suppleness which results from this mobility corresponds to the physiologic needs, and constitutes one of the most essential conditions for gracefulness of carriage. The movements of extension of the chest are rendered possible by the action of the muscles of the back, which hold the trunk erect and extend the vertebral column. When the corset is applied, the compression and constriction fix all those portions of the muscles at and below the waist; the action of the muscles between the chest and pelvis is diminished at least one-half, so that these muscles become atrophied from disuse, and when the corseted woman wishes to straighten up the movement must be executed by the entire trunk. [Illustration: Fig. 17.—Skeleton of head and trunk (O’Followell).]