Outlines of human physiology . xed. The twenty-four ribs are individuallymoveable upon the spine in every direction, but to a de-gree extremely limited. The seven uppermost on eitherside, or the true ribs, are let in by slips of cartilageinto oval fossulse along the side of the sternum, whichthey support. The five lower, or false ribs, are at-tached each to that above. The ribs and sternum areslight and fragile bones. In composition they derivestrength from their external convexity, and from theirnumerous and elastic joints. An imaginary plane carried through the first dorsalvertebra, through
Outlines of human physiology . xed. The twenty-four ribs are individuallymoveable upon the spine in every direction, but to a de-gree extremely limited. The seven uppermost on eitherside, or the true ribs, are let in by slips of cartilageinto oval fossulse along the side of the sternum, whichthey support. The five lower, or false ribs, are at-tached each to that above. The ribs and sternum areslight and fragile bones. In composition they derivestrength from their external convexity, and from theirnumerous and elastic joints. An imaginary plane carried through the first dorsalvertebra, through both ar-ticular extremities of thefirst rib of either side, andthrough the upper part ofthe sternum, would slantobliquely downwards andforwards. By the move-ment of each first rib uponits spinal joint sufficientlyto raise the upper margin ofthe sternum to the heightof the first dorsal vertebra,the imaginary plane wouldbecome horizontal. In manthis motion of the first ribis very limited; but it is obvious, that in proportion as. Form of the Chest. 57 it takes place, the vertical distance of the sternum fromthe spine, or the depth of the chest, becomes six lower true ribs admit of the same kind ofmotion upon their vertebral joints, and contribute toraise and carry forward the middle and lower part ofthe sternum for the same purpose. By this provision, all the muscles of the trunk, thelower attachment of which is to the ribs, are renderedcapable of increasing the depth of the chest, or its dia-meter from before backwards ; and the opposite class ofmuscles, of diminishing the area of the chest in thesame dimensions. .11 the ribs, but the first, admit of a limited degreeof rotation upon their verte-bral and sternal marks, even in thefcetal state, the limited de-gree of motion, which the firstrib is intended to enjoy, byforming its cartilage of onepiece with the sternum, towhich the cartilages of thesucceeding ribs are alreadyarticulated by moveablejoints
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Keywords: ., bookcentury1800, bookidoutlinesofhumanp00, booksubjectphysiology
