. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 1052 THORAX. a, obliquity in contrary directions. b, degrees of obliquity in each direction. Fig. 694. AG- BG- The perpendicular tension (L o, fig. 694.) produces but one effect, that of approxi- mating the two bars A c and B D, because the force of L o is acting upon A L and B o, levers of the same length, their movements being the same they would meet in the middle dis- tance at s. But if the bars are kept parallel by a rigid link like s,fig. 687. the perpendicular ten- sion would produce no apparent effect upon the tw
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 1052 THORAX. a, obliquity in contrary directions. b, degrees of obliquity in each direction. Fig. 694. AG- BG- The perpendicular tension (L o, fig. 694.) produces but one effect, that of approxi- mating the two bars A c and B D, because the force of L o is acting upon A L and B o, levers of the same length, their movements being the same they would meet in the middle dis- tance at s. But if the bars are kept parallel by a rigid link like s,fig. 687. the perpendicular ten- sion would produce no apparent effect upon the two bars. They might be rotated in any direc- tion, and the tension would remain of the same length ; for example, in Jig. 695. let t 2 be the perpendicular tension between the bars A B c D, move the bars to s or s', and the ten- Jig. sion is the same length, k k k, &c., may represent different places in the rotation, at each of which the tension t or k is the same length, although the bars at s, t 2, and s' are at different perpendicular distances from each other. A rigid connective, as wood or wire, may be substituted for the tension, an- this will equally allow of the bars being rod tated, and consequently changing their per- pendicular distances to each other. Hence it will be seen, that each of the lines k k k, are of the same length, although the two se- micircular lines describing the revolution of the bars are constantly changing in their re- lative distance to each othe We then seer, the possibility of having a rigid body connect- ing two bars, which shall nevertheless recede and approximate each other. From this we may gather, that though the sternum is rigid, and the cartilages, perhaps, ossified, the ribs may nevertheless maintain the capability of altering the breadth of their intercostal spaces. Perpendicular tension, therefore, like L o, (parallel to A B,) cannot rotate the bars, be- cause they never change their length. All tensions are oblique which ha
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