THE PHALANGES OF THE HAND 205 



in the other two rows, a double concavity, separated by a longitudinal median 

 ridge, extending from before backward. The distal extremity of the first phalanx 

 of the thumb and of the first and second phalanx of each of the fingers is smaller 

 than the base, and terminates in two small, lateral condyles, separated by a slight 

 groove (trochlea phalangis)', the articular surface being prolonged farther forward 

 on the palmar than on the dorsal surface, especially in the first row. 



The lingual phalanges (distal) are convex on their dorsal, flat on their palmar, 

 surfaces; they are recognized by their small size and by a roughened, elevated 

 surface of a horseshoe form on the palmar aspect of their ungual extremity (tuber- 

 ositas unguicularis), which serves to support the sensitive pulp of the finger. 



Articulations. The first row, with the metacarpal bones and the second row of phalanges; 

 the second row, with the first and third; the third, with the second row. 



Attachment of Muscles. To the base of the first phalanx of the thumb, five muscles the 

 xtensor brevis pollicis, Flexor brevis pollicis, Adductor pollicis, Adductores transversus and 

 )bliquus pollicis. To the second phalanx, two the Flexor longus pollicis and the Extensor 



ngus pollicis. To the base of the first phalanx of the index finger, the First dorsal and the First 

 almar interosseous; to that of the middle finger, the Second and Third dorsal interosseous ; 

 that of the ring finger, the Fourth dorsal and the Second palmar interossei; and to 

 lat of the little finger, the Third palmar interosseous, the Flexor brevis minimi digiti, and 

 bductor minimi digiti. To the second phalanges, the Flexor sublimis digitorum, Extensor 

 ammunis digitorum, and, in addition, the Extensor indicis to the index finger, the Extensor 

 linimi digiti to the little finger. To the third phalanges, the Flexor profundus digitorum and 

 ixtensor communis digitorum. 



Surface Form of Carpal and Metacarpal Bones and of the Phalanges. On the 

 ont of the wrist are two subcutaneous eminences, one on the radial side, the larger and 

 atter, due to the tuberosity of the scaphoid and the ridge on the trapezium; the other, on 

 ulnar side, caused by the pisiform bone. The tubercle of the scaphoid may be felt just 

 elow and in front of the apex of the styloid process of the radius. It is best perceived by 

 ^tending the hand on the forearm. Immediately below may be felt another prominence, better 

 larked than the tubercle; this is the ridge on the trapezium which gives attachment to some of 

 le short muscles of the thumb. On the inner side of the front of the wrist the pisiform bone 

 lay be felt, forming a small but prominent projection in this situation. It is some distance below 

 .styloid process of the ulna, and may be said to be just below the level of the styloid process of 

 ic radius. The rest of the front of the carpus is covered by tendons and the annular ligament, 

 nd entirely concealed, with the exception of the hooked process of the unciform, which can only 

 e made out with difficulty. The back of the carpus is convex and covered by the Extensor ten- 

 ons, so that none of the posterior surfaces of the bones are to be felt, with the exception of the 

 imeiform on the inner side. Below the carpus the dorsal surfaces of the metacarpal bones, 

 xcept the fifth, are covered by tendons, and are scarcely visible except in very thin hands. The 

 orsal surface of the fifth is, however, subcutaneous throughout almost its whole length, and mav 

 e plainly perceived and felt. In addition to this, slightly external to the middle line of the hand, 



a prominence, frequently well marked, but occasionally indistinct, formed by the base of the 

 ictacarpal of the middle finger. The heads of the metacarpal bones may be plainly felt and seen, 

 aunded in contour and standing out in bold relief under the skin, when the fist is clenched. It 

 lould be borne in mind that when the fingers are flexed on the hand, the articular surfaces of 

 xe first phalanges glide off the heads of the metacarpal bones on to their anterior surfaces, so 

 lat the head of these bones form the prominence of the knuckles and receive the force of anv 

 low which may be given. The head of the third metacarpal bone is the most prominent, and 

 veives the greater part of the shock of the blow. This bone articulates with the os magnum, 

 ) that the concussion is carried through this bone to the scaphoid and semilunar, with which the 

 gad of the os magnum articulates, and by these bones is transferred to the radius, along which 



may be carried to the capitellum of the humerus. The enlarged extremities of the phalanges 

 lay be plainly felt; they form the joints of the fingers. When the digits are bent the proximal 

 halanges of the joints form prominences, which in the joint between the first and second pha- 

 inges is slightly hollowed, in accordance with the grooved shape of their articular surfaces, 

 le at the last row the prominence is flattened and square-shaped. In the palm of the hand 

 le four inner metafiwpal bones are covered by muscles, tendons, and the palmar fascia, and no 

 art of them but their heads is to be distinguished. With regard to the thumb, on the dorsal 

 spect the base of the metacarpal bone forms a prominence below the styloid process of the radius; 

 le shaft is to be felt, covered by tendons, terminating at its head in a flattened prominence, in 

 ront of which can be felt the sesamoid bones. 



Applied Anatomy. The carpal bones are not very liable to fracture, except from extreme 

 iolence, when the parts may be so comminuted as to necessitate amputation. Occasionally 



