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line, the more direct is the transmission of the weight to the ground, and the lighter the burden. At the same time the whole trunk above the angle of the two lines of obliquity is thrown off to the side opposite to the weight, and the arm, acting by its great length as a lever, affords additional relief by being extended horizontally at its full length from the body.

The effect of this exercise on the boy in question was a double distortion. 1st, The lumbar vertebrae were arched from the basket; and 2dly, the dorsal were arched towards it. In this example the dorsal arch was in reality consecutive, and not exactly contemporaneous with the first or lumbar curve, because in the continued effort of carrying the weight, the head as well as the body was inclined from the object; and it was not until the boy was relieved from the burden, that the dorsal curve would commence. But all this was the product of muscular effort, exerted, as is evident, with a view to counterbalance a weight applied on one side of the body only, The case of a boy, now in St. Bartholomew's Hospital, is peculiar, inasmuch as it presents an example of great sigmoid curvature, the product of causes both active and passive.

George Chandler, aged 17, a chimney-sweeper,

Was engaged from the years of his childhood iii carrying a weight, consisting of some of the appurtenances of his trade, varying from ten to six pounds, on his left shoulder, possibly with a view to retain free action of the right arm. The immediate effect of such a weight has been already alluded to: the weighted shoulder was drawn towards the mesial line or centre of gravitation J that of the opposite side being depressed below its level. The spine became early distorted in the region in which invariably from such causes the influence of superincumbent weight must be felt, viz. the lumbar.

Thus far in the history of his case the condition was passive. The right mass of lumbar muscles raised the weight towards the centre, and continued mere observers of the result. After the boy had pursued this employment for many years he was engaged to carry a heavy basket about the town with his father, for the sale of fruit in the street. The father observed that the boy invariably employed the left arm for the occupation, and when desired to change the sides for their mutual relief, as invariably refused, finding that he was unequal to the effort; and well might he be so, for his body was already distorted by the long continuance of his former occupation. His spine .was greatly inclined from the perpendicular to the right side, and of course he was totally in-capacitated for such an effort, except with the left arm.

This form of distortion is the result of weight of any kind or form, suspended from the side of the body by the arm, which either from its amount, or from its encroachment on the legs in progression, and on which the stability of the person depends, demands a muscular effort to compensate for its tendency to draw the body in the opposite direction. This observation will apply to any weighty object carried and supported by one arm, if that side only of the body be continuously employed. Much, however, depends on the form and size of the object. A weight of twenty pounds in a plate of metal carried with its flat surface close to the leg, would incline the body in a much less considerable degree than a rounded object of the same weight, such as a pail of water; because, on the principle previously adverted to, the nearer the arm with its appended weight form a line parallel to the adjoining leg, the lighter the burden, or, in other words, the more closely does it hang to the centre of gravity.

But we find one form of lateral curvature dependent on muscular effort, and on that only. It is found prevalent among artisans, and confined, from obvious circumstances, to males; and of these only the young, rarely appearing at a later age than about twenty-five or twenty-eight. It is produced by violent and continued muscular exertion required in pulling, and is frequent among printers, and others engaged in similar occupations. These examples are furnished from that branch of the trade which consists in working at the press—a duty that commonly devolves on young men, under the age above mentioned. This instrument requires great muscular power and continuous exertion. It is worked by means of a pole or bar, which is drawn forcibly backwards by the right hand, the left being engaged in steadying the body against the press. The muscular agents which are employed, are those muscles that retract the scapula in the direction of the spine, namely, the two rhomboidei, the levator scapulae, the trapezius, and latissimus dorsi. Nearly all these muscles arise from the spinous processes of the vertebrae, which, by long traction, yield to the effort, and arch the dorsal portion of the column towards the limb. Of these we see various examples, the characteristics of which are, an inconsiderable lumbar curve, great muscular development, and distortion of the chest proportionate to the dorsal curve, and often very great. But the examples of this form of curvature are confined to one class of persons, and very rarely include females, or, indeed, males occupying a respectable station in life.

Many forms of curvature, especially those now under consideration, from great muscular exertion, present on examination some deceptive characters well worthy of attention. In the curvature from superincumbent weight, whether by the body itself, or by any artificial addition, the muscles of the loins are rather reduced than otherwise within their natural proportions, because the weight having been equalized at the expense of the natural form of the column while at rest, the muscles have nothing to do but to accommodate themselves to the change. But when the curve is primarily and principally dorsal, then the compensation in weight by the formation of an opposite curve is made by muscular contraction; and the muscles on the convex side of the curve in the loins are enlarged or hypertrophied in their whole extent as high as the dorsal curve. This, however, is an effect, and not a cause; for as the weight of the trunk is dragged from the centre of gravity by the projection of the dorsal curve, so the muscles which are opposed to it, become necessarily larger, in virtue of their increased duty. When the trunk under such circumstances is forcibly raised by the hands, the mass of muscles on the convex side rises most prominently on the surface, and the disparity of the two muscular columns becomes immediately apparent. The same remark will apply to the upper part of the same mass which is opposite the superior curve on

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