. The anatomy of the human body. Human anatomy; Anatomy. 170 ARTHROLOGY. transmitted to the foot, but also performs a very active part in the movements of pro- gression ; it is therefore so constructed as to unite great strength with the capabiUty of tolerably extensive motion. With regard to strength, the following arrangements should be noticed as especially ad- vantageous : 1. The leg being articulated with the foot at a right angle, transmits the weight of the body directly to it, and this transmission being effected in the perpendicular direction, i. e., in a direction in which the articu
. The anatomy of the human body. Human anatomy; Anatomy. 170 ARTHROLOGY. transmitted to the foot, but also performs a very active part in the movements of pro- gression ; it is therefore so constructed as to unite great strength with the capabiUty of tolerably extensive motion. With regard to strength, the following arrangements should be noticed as especially ad- vantageous : 1. The leg being articulated with the foot at a right angle, transmits the weight of the body directly to it, and this transmission being effected in the perpendicular direction, i. e., in a direction in which the articular surfaces mutually oppose each other, has no tendency either to produce fatigue or to rupture the ligaments. The perpendic- ular position of the leg upon the foot during standing is worthy of notice, because of it- self it proves that man was intended for the erect posture, since in this attitude alone does the entire inferior surface of the foot rest upon the ground. It should be also re- marked, that there is no other articulation, excepting that of the head upon the verte- bral column, in which the parts united are habitually perpendicular to each other. 2. The dovetailing eifected at this joint, by the reception of the astragalus into the socket, formed by the bones of the leg, is also highly conducive to its strength. This dovetail- ing results both from the pulley-like surface of the astragalus, and from the angular form of the tibio-fibular socket; and it should be observed, that this latter condition is, as it were, peculiar to the ankle-joint, for in no other do we meet with such abrupt angles. With regard to mobility, the tibio-tarsal articulation admits of flexion and extension. There is no lateral motion, the movements of the foot in this direction being almost ex- clusively performed at the tarsal joints. In flexion, the astragalus glides backward upon the tibia and fibula, and the back part of the pulley projects behind. Luxation, from an excess of this movemen
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