The lungs, heart, and great blood-vessels are placed in and completely fill an air-tight, distensiblecage, which is most distensible at its base.
The least chest girth of the adult woman-- that is, the under-arm girth around the chest-- that is consistent with health is twenty-eight inches; and this girth must be enlarged three inches in forced inspiration. In ordinary respiration the waist expansion should be one-half to one inch, while during great muscular activity it should be from one and a half to three or four inches. One-third of the lungs lie below the point of beginning corset pressure, so that with tight corsets this amount of lung substance must be more or less useless.
It is self-evident that any restriction placed about the waist, by preventing the full expansion of the ribs and the descent of the diaphragm, will further embarrass the heart's action by diminishing the amount of room it has to work in, at the same time that it diminishes the amount of oxygen which is inspired. Fresh air is by far the most important part of the daily food. It is in the lungs that the blood throws off its carbonic acid and other impurities; but it is able to do this only when the lungs are supplied with an abundance of oxygen. Every inch which a woman adds to her chest measure adds to the measure of her days.
Great physical injury has followed women playing lawn-tennis while tightly corseted. And although dancing is a much milder exercise, since it frequently takes place in an overheated and poorly ventilated room, fatal results occasionally occur from the same cause.
Standing erect calls into action almost all the muscles of the trunk, neck, and lower extremities. So long as the line of gravity falls within the area of the feet, the muscular effort required is so slight that it is little more than the tonicity contained in all living muscle. The greater the displacement of the line of gravity, the greater the muscular effort required to maintain the equilibrium of the body. Up to a certain extent, exercising the muscle develops the strength and size of the muscle. On the other hand, when a muscle within the body is unused, it wastes; when used within certain limits, it grows. But when the corset splint is applied to the body of the young girl, it supplants the functions of the abdominal and back muscles, which is to hold the trunk erect, and these muscles gradually grow weak and waste. And so the liability to the various spinal curvatures is increased.