170 



THE SKELETON. 



joints of the fingers. When the digits are bent the proximal phalanges of the joints form 

 prominences, which in the joint between the first and second phalanges is slightly hollowed, in 

 accordance with the grooved shape of their articular surfaces, whilst at the last ro/sSnthe 

 prominence is flattened and square-shaped. In the palm of the hand the four inner metacarpal 

 bones are covered by muscles, tendons, and the palmar fascia, and no part of them but their 

 heads is to be distinguished. With regard to the thumb, on the dorsal aspect the base of the 

 metacarpal bone forms a prominence below the styloid process of the radius ; the shaft is to be 

 felt, covered by tendons, terminating at its head in a flattened prominence, .in front of which can 

 be felt the sesamoid bones. 



Surgical Anatomy. The carpal bones are little liable to fracture, except from extreme 

 violence, when the parts are so comminuted as to necessitate amputation. Occasionally they are 

 the seat of tubercular disease. The metacarpal bone and the phalanges are not unfrequently 

 broken from direct violence. The first metacarpal bone is the one most commonly fractured ; 

 then the second, the fourth, and the fifth, the third being the one least frequently broken. 

 There are two diseases of the metacarpal bones and phalanges which require special mention on 

 account of the frequency of their occurrence. One is tubercular dactylitis, consisting in a 

 deposit of tubercular material in the medullary canal, expanding the bone, with subsequent 

 caseation and resulting necrosis. The other is chondroma, which is perhaps more frequently 

 found in connection with the metacarpal bones and phalanges than with any other bones. 

 They are commonly multiple, and may spring either from the medullary canal or from the 

 periosteum. 



Development of the Bones of 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. 119): In the 



Carpus. 



One centre for each bone. 

 All cartilaginous at birth. 



Metacarpus. 



Two centres for each bone : 

 One for shaft, 

 One for digital extremity, 

 except first. 



Phalanges. 



Two centres for each bone : 

 One for shaft, 

 One for metacarpal 

 extremity. 



Appears 3rd year. 



Unite 20th year. 

 .Appears 8th week. 



Appears Si'd-Uh 



year. 



~~ \ Unite I8lh 

 "''f ) year. 



-Appears Uh-5th year. 



Unite 18th-20th year. 

 ' Appears 8th week. 



Appears Uh-5th year. 

 \ Unite 18th-20 year. 

 'Appears 8th week. 



FIG. 119. Plan of the development of the hand. 



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

 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 



