226 THE SKELETON. 



PHALANGES. 



The Phalanges 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 down- 

 wards, is convex posteriorly, concave in front from above downwards, 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 backwards ; and the same extremity in the other two 

 rows, a double concavity separated by a longitudinal median ridge, extending 

 from before backwards. The digital extremities are smaller than the others, 

 and terminate, in the first and second row, in two small lateral condyles, sepa- 

 rated by a slight groove; the articular surface being prolonged farther forwards 

 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 sur- 

 faces ; 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, 

 which serves to support the sensitive pulp of the finger. 



Articulatfdns. 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, four 

 muscles : the Extensor Prirni Internodii Pollicis, Flexor Brevis Pollicis, Ab- 

 ductor Pollicis, Adductor Pollicis. To the second phalanx, two : the Flexor 

 Longus Pollicis, and the Extensor Secundi Internodii. 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 Digitorum, 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. 



DEVELOPMENT OF THE BONES OP THE HAND. 



The Carpal Bones are each developed by a single centre. At birth, they are 

 all cartilaginous. Ossification proceeds in the following order (Fig. 163): in 

 the os magnum and unciform an ossific point appears during the first year, 

 the former preceding the latter; in the cuneiform, at the third year; in the 

 trapezium and semilunar, at the fifth year, the former preceding the latter; in 

 the scaphoid, at the sixth year ; in the trapezoid, during the eighth year ; and 

 in the pisiform, about the twelfth year. 



The Metacarpal Bones are each developed by two centres : one for the shaft, 

 and one for the digital extremity, for the four inner metacarpal bones ; one for 

 the shaft, and one for the base, for the metacarpal bone of the thumb, which 

 in this respect resembles the phalanges. Ossification commences in the centre 

 of the shaft about the sixth week, and gradually proceeds to either end of the 

 bone ; about the third year the digital extremities of the four inner metacarpal 

 bones, and the base of the first metacarpal, commence to ossify, and they unite 

 about the twentieth year. 



The Phalanges are each developed by two centres : one for the shaft, and one 

 for the base. Ossification commences in the shaft, in all three rows, at about 

 the sixth week, and gradually involves the whole of the bone, excepting the 

 upper extremity. Ossification of the base commences in the first row between 



