238 THE UPPEE LIMB IN MAN. 



that the movements of pronation and supination are most 

 exactly performed. In the ape, the radial articular surface 

 extends further backwards, so that it takes a share in the 

 flexion and extension movements of the elbow joint. 



8.—77ie Rand. 



a. I shall confine my comparison of the human hand to 

 the so-called hand of the ape ; and for the purpose of bring- 

 ing before you in a distinct manner the principle which deter- 

 mines the construction of the human hand, I shall confine 

 my statements to such features of its structure as bear directly 

 on that principle. 



b. The human hand is the only perfect or complete hand. 

 In no other is there such a freely moveable thumb, capable of 

 such complete opposition, which is provided for by the saddle- 

 shaped surfaces of its carpo-metacarpal joint. The opposition 

 of the thumb must be distinguished from the apposition of 

 the great toe, the tarso-metatarsal joint of which admits of 



movements in one plane only. The 

 i j peculiar obliquity of the metacarpo- 



i j i phalangeal joints of the four fingers 



middle extend downwards into the 

 palm towards the thumb ; that of the 

 ring partially, and that of the little 

 considerably downwards, and towards 

 the ulnar side of the palm. It is owing 

 to this that the little finger possesses 

 Fi the power of being opposed to the 



outline diagram of the skeleton thumb. When the hand is clenched, 



of the human hand. The dotted 



lines indicate the direction of the ti ie points of the fingers tend to the 



movements at the metacarpo- x ° 



phalangeal joints. ^fa^ gide> J Q ^ y^ Q f fa e palm 



certain folds may be seen, which are indicative of the effects 

 produced on the skin by the movements of the joints. 1st, 

 the great oblique fold for the thumb. 2d and 3d, two oblique 



i» 



