OF THE PELVIS. 41 



in this disease, being constantly pressed between two opposing forces 

 must give way in that direction in which the strongest force operates, 

 or towards the point where tliere is the least resistance. 



102. Thus, admitting that the softening of the bones is every 

 where equally great, that the child is standing on its feet, and rests 

 with the same pressure on both legs, it is evident that the base of 

 the sacrum will be depressed towards the pubis, and the cotyloid 

 cavities will be pushed upwards towards the promontory. Hence, 

 there will be shortening of the sacro-pubic, as well as of the oblique 

 diameters: if the child stands on its feet, but leans more on one foot 

 than on the other, the oblique diameter of one side only will be 

 contracted; if he remains seated, the hollow of the sacrum will be- 

 come deeper, while the antero-posterior diameters of the two straits 

 will be lessened; if he be habitually laid upon his back, the curve 

 of the sacrum, instead of augmenting, will disappear, as v/ell as the 

 pelvi-vertebral angle, and the coccy-pubic diameter will generally 

 lose somewhat of its dimensions; a lateral posture will influence the 

 transverse diameters, &c. 



103. Although the weight of the body then will account for most 

 of the vicious forms of the pelvis, it must, nevertheless, be admitted 

 that their production is in certain cases singularly favored by the 

 active power of the muscles that surround the coxo-femoral articu- 

 lation; so much the more, as the bones, most commonly softened 

 only at some particular points, retain every where else all the solidity 

 that is desirable. 



104. After the first periods of childhood, the deformities of the 

 pelvis are almost always the result of a disease, as that malacosteon, 

 either general or partial, which is so common in England, of osteo- 

 malacia, of irregular action of the muscles, and of bad habits in 

 respect to attitude. It is thus that young girls, who, for the purpose 

 of increasing the prominence of their hips and the depth of the 

 lumbar hollow, keep the pelvis and head thrown strongly backwards 

 while they project the abdomen and breast as far forwards as possi- 

 ble, never think that for the purpose of obtaining some elegance of 

 form, they run the risk of being never able to become mothers, with- 

 out exposure to the greatest danger. 



105. In a diseased hip joint the head of the femur has been seen 

 to push the bottom of the acetabulum into the pelvis, and even to 

 pierce through the acetabulum. Madame Lachapelle gives the case 

 of a woman who was affected with a spontaneous luxation of the 

 thigh bone, and in which the false acetabulum projected so far into 

 the pelvic excavation as to interfere with the labor; the amputation 

 of a thigh, but not of a leg, in an adult woman, and a fortiori in a 

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