The Hand is essentially the organ of touch and of prehension. These functions devolve principally upon its anterior or palmar face. The nervous papillæ with which it is provided abound specially at the ends of the fingers, where they form furrows in elegant curves under the epidermis. The tendons in it are very numerous, and bound together by multiplied connections. Strong aponeuroses and sheaths, through which the tendons slide, make the skin compact, and combine to give unity to the general movements of the different parts of the organ, and independence to partial ones. A layer of adipose tissue, very close in texture, protects, without lessening its power or its delicacy, that network of muscles, vessels, and nerves, this apparatus which sometimes barely touches an object, and sometimes grasps it with such violent pressure. The hand, in fact, is either a delicate pincer or a powerful vice; it guides the burin of the engraver, which leaves behind it the finest trace, the hatchet of the carpenter and the axe of the woodman, whose blows are given with as much strength as skill The fingers of the sailor knot the heavy cordage, and those of the optician stretch a spider's thread, without breaking it, across the field of an astronomical telescope. The same organ can hold a switch, a club, a sword, a hammer, or a pen. It moulds itself to a body to ascertain its form; it comes to the aid of the eye in completing or rectifying its impressions, and in some cases even supplies its place. Thus the finger of the physician perceives on the surface of an organ the slightest inequality in relief; and the hand of Michael Angelo followed with enthusiasm the contour of the antique torso, which the eyes of the great artist could no longer contemplate.
But nothing gives a more complete idea of the perfection of the mechanism of the hand, than the execution of instrumental music. Examine an artist while he plays on a violin. His fingers rest upon the strings so as to leave them exactly of the length necessary for the tones they are to give. The half of a millimetre, more or less, greatly changes the true ness of the note; and a cord a millimetre out of place produces a note which even the unpractised ear recognizes as false. But the fingers fall upon the strings at precisely the point required. They run over them, succeeding each other with giddy rapidity, following every imaginable combination, and yet the hand gliding over the instrument incessantly changes its position. Sometimes a single finger produces an isolated note; sometimes two or three act simultaneously to produce a concord; while a fourth, striking the string with increasing rapidity, produces a trill which rivals that of the nightingale. And even this is not all. The other hand holds the bow, and the movements of the right arm must be in correspondence with those of the left hand; the coincidence between the movements of one hand and that of the other must be mathematically exact Add to these all the modifications necessary to produce the piano and the forte, to swell the sound or to let it the away—all, in a word, that constitutes musical expression, and it will be admitted that this mechanism is allied to the wonderful, and that it surpasses the most perfect productions of human art.
The agility and flexibility of the hands, the concordance and independence of their movements, is not less remarkable in the playing of the pianist How is it possible not to admire those two hands, both oftenest occupied together, and the action of which alternates or coincides with so much precision and rapidity; together they produce on an average from six to eight notes at a time—separating, approaching, crossing, and mingling their fingers, which move over the keys as if each one were completely independent of all the others? A skilful pianist produces about 640 notes a minute in medium time, and 960 in extremely quick time. These numbers give us an idea of the rapidity of movement which can be attained by the hand of man.
The devoted servant of the body, the hand which nourishes it knows also how to defend it. It has been said that man is created without arms. What then is the hand which enables him to construct and employ for his defence those ingenious and terrible machines, that hand which can at need itself become a formidable weapon? The poets have sung the praises of Pollux defending his own life and that of his companions with the arms which nature gave him; but if we admire Pollux battling with the Sicilian giant, we turn our eyes from the arena ensanguined by the gauntlet of Entellus. The soldier considers it an honour to employ with skill in the defence of his country the sword which she has intrusted to him; but he despises the arms and the trade of the gladiator.
The principal function of the upper limb is to remove objects from the body, and to draw them to it; but it can also remove the body from a fixed point, or approach it to one. It is in this way that the sailor raises himself on the rigging, or the gymnast on the trapeze; but the weight of the body is not in proportion to the strength of the limbs which raise it, and although exercise renders this effort less difficult by increasing the power of the muscles, it is evident that here the arm performs a function which does not devolve upon it chiefly, and which belongs to a more powerful member, of which we will now speak.