Lateral curvature of the spine and round shoulders . r twisting of the verte-bral bodies always accompanies or-ganic lateral curvature has been widelydiscussed from every point of view, andthe question has been much compli-cated by the abstruse reasoning appliedto its solution. The facts seem to bethese: the vertebral column is a flexibleweight-bearing rod curved in the an-tero-posterior plane by the physiolog-ical curves: in a column affected bylateral curvature it is now beginningto be curved to one side in some part ofits length. Growing bone, it has beenstated, is a plastic structure and w
Lateral curvature of the spine and round shoulders . r twisting of the verte-bral bodies always accompanies or-ganic lateral curvature has been widelydiscussed from every point of view, andthe question has been much compli-cated by the abstruse reasoning appliedto its solution. The facts seem to bethese: the vertebral column is a flexibleweight-bearing rod curved in the an-tero-posterior plane by the physiolog-ical curves: in a column affected bylateral curvature it is now beginningto be curved to one side in some part ofits length. Growing bone, it has beenstated, is a plastic structure and willyield to unequal conditions of weightor strain. This curved part of thecolumn being subject to unequal con-ditions of weight on the two sidestends to yield to the side and tochange its structure in accordance with these unequal conditionsof weight. But a plastic weight-bearing column already curved in one planecannot yield in another plane {, to the side) without twisting, andin this twist the vertebrae can turn in only one way, namely, away. Fk,, 3(1 —Experimental Scoli-osis IN A Young Dog ProducedBY Bandaging in a One-sided Posi-tion.— {Wulhtein.) 50 MECHANISM OF SCOLIOSIS from the greatest weight and pressure, which is, of course, on theconcave side of the lateral curve. If they were to turn toward themiddle line instead of away from it they would encounter the greaterinstead of the less resistance and have to raise the whole weight of theparts above them. In so far as they are plastic they will be com-pressed where the weight is greatest or on the concave side. Thedeformity of the vertebrse is therefore due to their plasticity yieldingto conditions of unequal strain, and turning where they must turnto escape. Double Curves.—^The explanation of a double curve is more diffi-cult. It has been observed that frequently a double organic curvegrows out of a single functional one, the reason for which will beexplained in the chapter on Description and Symptoms. It cann
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