ACTIONS OF THE HAND. 47 



interlaced and bound together by bands and aponeurotic 

 fibres, and from this results a more or less complete unity of 

 action. It is sometimes difficult to make a movement with 

 a single finger without the others taking part in it, as in 

 executing instrumental music, for instance ; but practice gives 

 to these movements perfect independence. The mechanism 

 of the movements of the hand has been made singularly clear 

 by the recent experiments of M. Duchenne of Boulogne, who 

 has succeeded in distinguishing by means of electricity, the 

 action not only of different orders of muscles, but also of 

 each particular one. Gerdy counts thirty-four distinct move- 

 ments of the hand, and if we include the combinations of 

 these different movements we shall reach a much higher 

 number. The opposition of the thumb to the other fingers, 

 alone or united, is of all these movements that which 

 especially characterizes the human hand, in which alone it 

 exists in its perfection. This action of the thumb results 

 from its length, from the first metacarpal bone not being 

 placed on the same plane as the other four, as is the case in 

 the monkey, and from the action of a muscle the long 

 flexor of the thumb peculiar to the human hand. This 

 muscle completes the action of the other motor of the 

 thumb, and permits man to hold a pen, a graver, or a needle ; 

 it gives to his hand the dexterity necessary in the execution 

 of the most delicate work; it is the attribute of his intelli- 

 gence. In repose the hand of man is presented in an 

 attitude half opposed to the thumb; but it is not so in the 

 monkey, even in the species most resembling man. It is 

 opposable in these animals, but much less so than in man; 

 and the five bones of the metacarpus being on the same 

 plane, the fingers or toes can be placed flat upon the 

 ground in walking, in which the four limbs always take part. 

 Properly speaking, then, the hand belongs to man alone, and 

 its conformation does not permit us to consider it as a nor- 

 mal organ of locomotion. It can by turns form itself into a 

 plane, round itself into a cylinder, hollow itself into a gutter^ 

 make the fingers spread like so many diverging rays, and 

 form, in the words of De Blainville, a compass with five 

 branches; it collects the fingers in the form of a cone, of a 



