200 



. SPECIAL ANATOMY OF THE SKELETON 



they are the seat of tuberculous disease. The metacarpal bones and the phalanges are not infre- 

 quently broken by direct violence. The first metacarpal bone is the one most commonly frac- 

 tured; 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 01 

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

 of tuberculous material in the medullary canal, expanding the bone, with subsequent caseatioi 

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

 connection with the metacarpal bones and phalanges than with any other bones. When chon 

 dromatous growth takes place there are usually multiple tumors, and they may spring eithei 

 from the medullary canal or from the periosteum. 



Development of the Bones of the Hand. The carpal bones are each developed from i 

 single centre. At birth they are all cartilaginous. Ossification proceeds in the following orde; 

 (Fig. 166): In the os magnum and unciform an ossific point appears during the first year, thi 

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

 at the fifth year, the latter preceding the former ; in the scaphoid, in the sixth to the eighth year 

 in the trapezoid, during the eighth year; and in the pisiform, about the twelfth year. 



Carpus. 



One centre for each bone. , 

 All cartilaginous at birth. <(", 



Metacarpus. 



Two centres for each bone : 

 One for shaft, 

 One for distal 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 Srd-Uh 



:ar. 



lie 18th-SOth 

 year. 



-Appears Uh-5th year. 

 } Unite 18th-20th year. 

 Appears 8th week. 



I 



Appears Uh-5th year. 

 Unite l8ih-W year. 

 * Appears 8th week. 



FIG. 166. Plan of the development of the bones of the hand. 



Occasionally an additional bone, the os centrale, is found in the carpus, lying between th 

 scaphoid, trapezoid, and os magnum. During the second month of fetal life it is represented b; 

 a small cartilaginous nodule, which, however, fuses with the cartilaginous scaphoid about th 

 third month. Sometimes the styloid process of the third metacarpal is detached and forms ai 

 additional ossicle. 



The metacarpal bones are each developed from two centres, one for the shaft and one fa 

 the distal extremity for the four inner metacarpal bones; one for the shaft and one for the bas 

 for the metacarpal bone of the thumb, which in this respect resembles the phalanges. 1 Ossi 



1 Allan Thomson has demonstrated the fact that the first metaearp.il bone is often developed from thre 

 centres; that is to say, there is a separate nucleus for the distal end, forming a distinct epiphysis, visible at th 

 age of seven or eight years. He also states that there are traces of a proximal epiphysis in the second meta 

 carpal bone. Journal of Anatomy and Physiology, 1809. 



