Researches in Obstetrics

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1868. Excerpt: ... The iliac beam may be regarded as a long bone, strengthened by the apposition of its ala. The weight or force to which it is subjected acts upon it at its two extremities, and not in the direction of its length, and with a degree of vantage not to be observed in any other bone of the body. It does, while growing, change in form under these forces, and, I believe, in consequence of them. A like change occurs in other long bones similarly treated, as in the femora of young lads who ride much on horseback. Moreover, when the iliac beams are inordinately subjected to the natural forces in youth, their bending increases to an abnormal extent, as happens in factory children who have never suffered from rachitis, and whose skeletons present no evidence of the previous existence of the disease.t In the field of pathology many illustrations occur, under the most varied circumstances, of the great influence of long-continued though slight mechanical forces in changing the shape of healthy bones. J It is indeed inconceivable that elastic living tissues should endure powerful and continued pressure without being greatly and permanently affected by it. The shape, says Dr. Humphry, of the bones (and here it may be remarked that the uniformity with which they acquire their proper shape is truly marvellous) must be due chiefly to those same developmental forces whereby the shape of the body generally is determined. Future investigation may point out the proximate causes by which shape is evolved: at present we have little or no clue to them. There are, however, some few secondary agents--assistants, as they may be termed, to the primary developmental processes--whose influence we can trace in moulding the shape, etc., of the bones: one of the chief of these is pressu...