Page:The New International Encyclopædia 1st ed. v. 09.djvu/576

* HAND. 522 HAND. produces an opposite efl'ect. rolling the radius and the liand back into the position of supination. ilence it is called a siipinaior muscle. The third is a very powerful muscle, termed tlie biceps (q.v. ). which not only bends the elbow, but, from the mode in which its tendon is inserted into the inner side of the radius, "also rotates the radius so as to supinate the hand; and it gives great power to that movement. When we turn a screw, or drive a gimlet, or draw' a cork, we al- ways employ the supinatiitg movement of the hand for the purpose : and all screws, gimlets, and implements of the like kind are made to turn in a manner suited to that movement of the right hand, because mechanicians have observed that we have more power to supinate the hand than to pronate it." Supination can only be per- formed to its full extent by man. and even in man it is not the natural or habitvial position ; monkeys can partially efl'ect the movement, and in most of the low'er animals the part correspond- ing anatomically to the hand is constantly in a state of pronation. The movements of which the hand itself, with- out reference to the arm, is capable, are very numerous, and in this respect difl'er considerably from the corresponding movements of the foot. Thus we can bend the fingers down upon the palm, or we can extend them be3'ond the straight line : we can separate them from one another to a considerable extent, and we can close them with considerable force. The wrist and hand are bent forward or flexed upon the forearm by three muscles, which pass downward from the inner condyle or expanded end of the humerus, and are termed the radial flexor, the ulnar flexor, and the long palmar muscles. The first two of these muscles are inserted into wrist-bones on the radial and ulnar sides respectively, while the third expands into a fan-like fascia or membrane in the palm of the hand, and thus serves both to support the skin of the palm and to protect the nerves and vessels which lie below it. Beneath the palmar fascia lie two sets of flexor muscles of the fingers, and they present so beautiful a mechanical arrangement as to merit special notice. The superficial or perforated flexor muscle passes down the front of the forearm and divides into four tendons, which become apparent after the removal of the palmar fascia, and are insert- ed into the second phalanges of the fingers, each tendon splitting at its termination, to give pas- sage to the similar tendons of the deep or per- forating flexor muscle, which passes from the upper part of the ulna to be inserted into the last phalanx of each finger. These flexor muscles are antagonized by the coynmon extensor muscle of the fingers, which, like the flexors, divides into four tendons, one for each finger. Besides these, there are a special extensor of the inde.x-finger. a series of muscles forming the ball of the thumb, which move that organ in itlmost every direction, anfl various small slips giving lateral and other movements to the fingers. The hand possesses marvelous adaptability to a great variety of iises. The fingers are fitted for grasping small objects, or for suspending the body from a horizontal bar. The hand may be made into a cup for conveying fluid to the mouth, or extended rigidly, as when swimming. A small needle may be used with great precision and deli- cacy in the same hand that wields a heavy sledge- hammer or holds a taut rein over the back of a turbulent horse. The great flexibility of the lingers and their capacity for training in accu- rate work is seen in their use in plaj'ing upon the violin or the piano. Some of the commonest daily uses of the hand consist of verj' intricate and complex working of groups of muscles in which coordination is exact. Controlling the pen- cil in drawing or writing, and rolling a cigarette may be cited as examples. It is imt strange, in view of its adaptability and capacity for such accurate adjustment, that the hand was thought in old times to be a reservoir of special force which passed out of it upon occasion. The 'lay- ing on of hands' for the cure of the sick, or for the transmission of a beneficent influence, is as old as the Scriptures ; and the touch of royalty was supposed to possess special virtue in healing scrofula, or 'king's evil.' The markings in the palm of the hand are supposed to be indications of the character and temperament, and disciples of palmistry (q.v. I believe they can read tlie secrets of the future in the records of palmar lines and folds. The papilhe on the skin of the finger-tips are arranged in concentric or ovoid lines. Probably these lines are never identical in dift'erent individuals. It is said that the Chinese use an impression of the papillary lines on the pulp of the thumb-tips as a means of identification : and it was seriously proposed in this country to add to the meas- urements of criminals by the Bertillon method impressions of their thumbs as an additional: standard of comparison and identification. The investigations of Francis Galton (q.v.) in this respect were noteworthy. Fingers dift'er much in their size and model, and give hands different expressions. From the natural position of the hand at rest may be inferred much concerning the temperament, genius, and mentality of its owner. This fact is well stated in Warner's Physical Expression (Xew York. 1886), one of the )nost original works on this subject. Eight- handedness is a natural condition, for which several causes have been assigned, no one of them being convincing. It has been considered due to a larger arterial supply to the right side; to "an innate tendency to a predominance of nutrition on the right side in foetal life" (Breschet) ; to the position of the fcetus in vtero: and to the as- sumed fact that the centre of gravity of the body lies on the right side. Left-handedness oc- curs in about 9 per cent, of human beings. There are many congenital and developmental anomalies encountered in a study of hands. In some rare cases the hand is wanting altogether. This condition is termed 'acheiria.' If one or more fingers be missing, the condition is termed 'ectrodactylism.' 'Hypophalangism' is the name given to the condition in which the number of phalanges in a finger is less than normal. 'Poly- cheiria' denotes a supernumerary hand ; 'poly- dactylism,' a supernumerary finger; 'polyphalan- gism.' the condition in which the number of phalanges in a finger is greater than normal. The union of fingers together, web fingers, or 'syndactylism.' also occurs; as well as cleft-hand, club-hand, and other deformities. In the disease acromegaly (q.v.) an enlargement of the hands takes place. Changes in the fingers and hands occur in many other diseases, as in myxoedema and syringomyelia (qq.v.). In pulmonary tuber-