OF THE MUSCLES. 225 



head on which it turns, without any motion of the 

 humerus ; and as the bones of the wrist are attached to 

 the lower end of this bone alone, and not to the ulna, c, 

 when the radius revolves, the whole hand turns with it. 

 This alternate rolling motion is called pronation and 

 supination. 



Motions of the Fingers. The motions of the fingers 

 do not merely result from the actions of the large mus- 

 cles, which lie on the fore arm, these being concerned 

 more especially in the stronger actions of the hand. 



The finer and more delicate motions of the fingers are 

 performed by small muscles, situated in the palm, and 

 between the bones of the hand, and by which the fingers 

 are expanded, and moved in all directions with wonder- 

 ful quickness. 



These are the organs which give the hand the power 

 of performing all its nicest motions, and by which we 

 are enabled to execute our finest works ; such as engra- 

 ving, writing, sewing, and painting ; in all these cases 

 the motions are directed by the will, while the instru- 

 ment is guided by the eye. 



The Thumb. The thumb is the antagonist to the fin- 

 gers. On the length, strength, free lateral motion, and 

 perfect mobility of the thumb, depend the power of 

 the human hand. Without the fleshy ball of the thumb 

 the power of the fingers would avail nothing ; and 

 accordingly, the large ball, formed by the muscles of 

 the thumb, is the distinguishing character of the human 

 hand and especially that of an expert workman.* 



The Fingers of different lengths. Although the fin- 

 gers are of different lengths, yet when they are doubled 

 into the palm, their ends become parallel. This is 

 owing to their difference of length being chiefly in the 



To what bone is the wrist attached 1 By what organs are the finer 

 and more delicate motions of the hand performed 1 What is said of the 

 importance of the thumb to the perfection of the hand 7 



* Bell on the hand. 



