252 



PHYSIOLOGY AND HEALTH. 



The upper arm has a single bone, the humcncs, (Fig. 

 XXXII. h.) The fore-arm has two bones, the radius and the 

 ulna, (Fig. XXXII. i.) The wrist has eight bones, (Fig. 

 XXXVIII. c, e, c, c,) which are held so firmly together by 

 ligaments that they are rarely displaced. The hand is com- 

 posed of four bones, to which the fingers are attached, and 

 the bone to which the thumb is fixed, (Fig. XXXIX.) These 



FIG. XXXIX. Bones of the Hand. 



a, Wrist. 



b, b, Hand. 



c, c, c, c, Fingers. 



d, Thumb. 



are held more loosely together by ligaments, and enclosed in 

 one sheath of skin. Thejingers are each composed of three 

 bones, (Fig. XXXIX. c, c.) The hand is beautifully and 

 skilfully arranged and adapted to an almost infinite variety 

 of purposes. Its wonderful structure and multiplied uses 

 are suited to the exigencies of the mind which directs it, 

 and gives to man a superiority over all other animals. 



601. The lower extremity (Fig. XXXII.) is composed of 

 the thigh-bone, which is a single shaft, the knee-pan, the two 

 bones of the leg, the bones of the ankle, foot, and toes. 

 The foot (Fig. XL.) is composed of twelve bones. Seven of 

 these, bones are of irregular shape, and are arranged to form 

 the ankle and the arch, (Fig. XL. , 6, c, d, c,/, g.) The 

 other five bones are long. They are joined to the instep 





