MUSCULAR ACTION. 451 



Let him first grasp the upper arm firmly, and bend the 

 limbs, and he will at once find that the swelling of the muscle 

 shows the source of power. 



Then let him do the same, but grasp the fore-arm, and he 

 will find that the muscles are quiescent, showing that the 

 former set of muscles belong to the entire arm, and not to the 

 fingers, while the muscles of the lower arm have nothing to do 

 with the bending of that limb. 



Now let him grasp the fore-arm, and open and close kte 

 fingers, and he will feel a whole set of muscles rise, and swell 

 and harden under his grasp. Next let him bend his hand 

 inwards, and he will find that the fingers work perfectly well, 

 though the direction of force is changed. 



This is owing to a band of tendons passing across the 

 wrist, under which the finger-tendons play. The course of 

 the tendons is marked in the illustration by leaving them 

 white. 



The wondrous structure of the human hand and its multitu- 

 dinous tendons can only be appreciated by actual dissection, 

 but an idea of their variety and use may be obtained by watch- 

 ing the hands of a skilful pianoforte-player. This struck me 

 forcibly the first time that I ever heard Thalberg play. 



While on the subject of tendons, I may mention a curious case 

 A journeyman carpenter missed a blow with his axe, and 

 struck his left hand at the junction of the thumb and wrist. 

 The important tendon was severed, and the inner muscles, 

 having no counteracting force, dragged the thumb into the 

 hollow of the hand. 



To all appearance, the man could no longer earn a living as 

 a carpenter. But he would not be discouraged, and while he 

 was in hospital he borrowed a book, and studied the 

 anatomy of the human hand. By means of this knowledge he 

 constructed a sort of semi- glove, in which lie introduced pieces 

 of watch-spring, that supplied the place of the lost tendon. 



Not content with this, he studied Euclid for the purposes of 

 his trade, so as to get the most possible out of a piece of wood 

 of given dimensions, and be able to go straight to his mark by 

 a problem, instead of doing it slowly and clumsily with a two- 

 foot rule and a pair of compasses. When I saw him last he 

 was a master carpenter in a large and increasing business. 



