270 THE SKELETON. 



The Phalanges. 



The Phalanges (internodia) are the bones of the fingers ; they are fourteen in 

 number, three for each finger, and two for the thumb. They are long bones, and 

 present for examination a shaft and two extremities. The shaft tapers from 

 above downward, is convex posteriorly, concave in front from above downward, 

 flat from side to side, and marked laterally by rough ridges, which give attachment 

 to the fibrous sheaths of the Flexor tendons. The metacarpal extremity, or base, 

 in the first row presents an oval, concave, articular surface, broader from side to 

 side than from before backward ; and the same extremity in the other two rows, 

 a double concavity, separated by a longitudinal median ridge, extending from before 

 backward. The digital extremities are smaller than the others, and terminate, 

 in the first and second rows, in two small, lateral condyles, separated by a slight 

 groove ; the articular surface being prolonged farther forward on the palmar than 

 on the dorsal surface, especially in the first row. 



The Ungual Phalanges 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 lingual extremity, 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 Extensor brevis pollicis, Flexor brevis pollicis, Abductor pollicis, 

 Adductor transversus and obliquus pollicis. To the second phalanx, two : the 

 Flexor longus pollicis and the Extensor longus pollicis. To the base of the first 

 phalanx of the index finger, the First dorsal and the First palmar interosseous ; to 

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

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

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

 and Abductor minimi digiti. To the second phalanges, the Flexor sublimis digi- 

 torum, Extensor communis digitorum, and, in addition, the Extensor indicis to 

 the index finger, the Extensor minimi digiti to the little finger. To the third 

 phalanges, the Flexor profundus digitorum and Extensor communis digitorum. 



Surface Form. On the front of the wrist are two subcutaneous eminences, one on the 

 radial side, the larger and flatter, due to the tuberosity of the scaphoid and the ridge on the 

 trapezium ; the other, on the ulnar side, caused by the pisiform bone. The tubercle of the 

 scaphoid is to be felt just below and in front of the apex of the styloid process of the radius. It 

 is best perceived by extending the hand on the forearm. Immediately below is to be felt 

 another prominence, better marked than the tubercle ; this is the ridge on the trapezium which 

 gives attachment to some of the short muscles of the thumb. On the inner side of the front of 

 the wrist the pisiform bone is to be felt, forming a small but prominent projection in this situa- 

 tion. It is some distance below the styloid process of the ulna, and may be said to be just below 

 the level of the styloid process of the radius. The rest of the front of the carpus is covered by 

 tendons and the annular ligament, and entirely concealed, with the exception of the hooked pro- 

 cess of the unciform, which can only be made out with difficulty. The back of the carpus is 

 convex and covered by the Extensor tendons, so that none of the posterior surfaces of the bones 

 are to be felt, with the exception of the cuneiform on the inner side. Below the carpus the 

 dorsal surfaces of the metacarpal bones, except the fifth, are covered by tendons, and are scarcely 

 visible except in very thin hands. The dorsal surface of the fifth is, however, subcutaneous 

 throughout almost its whole length, and is plainly to be perceived and felt. In addition to this, 

 slightly external to the middle line of the hand, is a prominence, frequently well marked, but 

 occasionally indistinct, formed by the base of the metacarpal of the middle finger. The heads of 

 the metacarpal bones are plainly to be felt and seen, rounded in contour and standing out in bold 

 relief under the skin, when the fist is clenched. It should be borne in mind that when the fin- 

 gers are flexed on the hand, the articular surfaces of the first phalanges glide off the heads of the 

 metacarpal bones on to their anterior surfaces, so that the heads of these bones form the prom- 

 inence of the knuckles and receive the force of any blow which may be given. The head of the 

 third metacarpal bone is the most prominent, and receives the greater part of the shock of the 

 blow. This bone articulates with the os magnum, so that the concussion is carried through this 

 bone to the scaphoid and semilunar, with which the head of the os magnum articulates, and by 

 these bones is transferred to the radius, along which it may be carried to the capitellum of the 

 humerus. The enlarged extremities of the phalanges are to be plainly felt: they form the 



