FUNCTIONS OF LOCOMOTION. 77 



latter is the only one which is articulated with the 

 humerus; its upper end forms the projection of the 

 elbow. The other bone, the radius, is articulated with 

 the ulna above, and by its lower extremity supports the 

 hand; it turns freely around the ulna. This simple 

 but ingenious mechanism allows us to make easily the 

 various movements and changes of position of the hand. 



The hand includes the wrist or carpal bones, eight in 

 number, and all belonging to the class of short bones, 

 the five metacarpal bones that form the framework of 

 the palm of the hand, and the phalanges, of which there 

 are three in each finger, except the thumb, which has 

 only two. 



The lower limb, correctly speaking, is composed of the 

 thigh, the leg, and the foot. 



The femur, or thigh-bone, is articulated with the iliac 

 bone above, and with the tibia below. It is the largest 

 bone of the skeleton. Its somewhat arched form con- 

 tributes to increase the supporting base of the body, and 

 renders the erect position easier. 



The leg has two bones, the tibia, inside, and the fibula, 

 outside ; the latter takes but a secondary part. The ar- 

 ticulation of the tibia and femur is protected by the pa- 

 tella or knee-pan, a small, flat bone, in which anatomists 

 find the analogue of the eminence of the ulna, which 

 forms the elbow. 



The foot includes the tarsal bones, of which there are 

 but seven (two of them are joined together in a single 

 bone that forms the heel-bone or calcaneum). five meta- 

 tarsal bonos like the metacarpals, and the phalanges of 

 the toes corresponding in number and distribution to 

 those of the fingers. 



Locomotion. The study of locomotion is that of the 



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