Human physiology : designed for colleges and the higher classes in schools and for general reading . c a h WALLS OF THE CHEST. of the chest, certain muscles, i, extending from the spinalcolumn in the neck to the first rib. When these contract, theeffect will be to raise this first rib, and all the others, beingattached to it, of course follow. And, as the ribs, as you seein Fig. 37, slant downwards from the spine toward the front,the result will be, that all the ribs will be carried together for-ward and upward. This result is the more effectually securedby muscles which pass from rib to rib,
Human physiology : designed for colleges and the higher classes in schools and for general reading . c a h WALLS OF THE CHEST. of the chest, certain muscles, i, extending from the spinalcolumn in the neck to the first rib. When these contract, theeffect will be to raise this first rib, and all the others, beingattached to it, of course follow. And, as the ribs, as you seein Fig. 37, slant downwards from the spine toward the front,the result will be, that all the ribs will be carried together for-ward and upward. This result is the more effectually securedby muscles which pass from rib to rib, as seen at e, e, e, e. Inthis Figure, the ribs, c, c, c, are left bare on the left side, to show RESPIRATION. 93 Arrangement of muscles between the ribs. the arch of the diaphragm, ff, the dotted line indicating it onthe right side. 137. There are two layers of muscles connecting the ribs,the fibres of which cross each other, as represented at M, inFig. 41. R R are parts of two ribs. The spaces between the FIG. ribs are filled with muscular fibres, arranged as represented inin the Figure. If the fibres were straight, as at L, they couldnot bring the ribs as near together as the oblique fibres , as muscles can not shorten themselves, at the farthest, morethan one-third of their length, the straight fibres could bringthe ribs only one-third nearer together, while it is obvious thatthe oblique fibres, with the same contraction, can do muchmore than that. These muscles between the ribs not only,then, help to raise all the ribs as a body, as mentioned in § 136,but they bring each rib nearer to the one above it. This in-creases the expansion of the chest, especially as the ribs are sojoined to the spine, that if a rib be moved upward, it must becarried outward as well as forward. You can see, then, thatby the operation of these muscles in the neck and between theribs, the diameter of the chest will be increased from front torear, and also from side to side. 138. The chest
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