THE CAEPUS. 



217 



month of intra-uterine life. At birth the 



Fuses with shaft 18-20 years body is well formed ; its proximal and distal 

 extremities are capped with cartilage, and 

 the tuberosity is beginning to appear. A 

 secondary centre appears in the cartilage 

 of the distal extremity about the second or 

 third year; this does not unite with the 

 body until the twentieth or twenty-fifth 

 year, somewhat earlier in the female. From 

 this the carpal and ulnar articular surfaces 

 are formed. The centre for the head 

 appears from the fifth to the seventh year, 

 and fuses with the neck about the age of 

 eighteen or twenty. It forms the capitular 

 articular surface and combines with the neck 

 to form the area for articulation with the 

 radial notch of the ulna. A scale-like 



Appears about 

 2-3 years 



Unites with shaft 20-25 years 



At Birth. About 12 years. About 16 years. 



FIG. 208. THE OSSIFICATION OF THE EADIUS. 



epiphysis capping the summit of the 

 tuberosity has been described ; this ap- 

 pears about the fourteenth or fifteenth 

 year, and rapidly fuses 

 with that process. 



THE BONES OF 

 THE HAND. 



I. METACARPAL 



SESAMOID BONES 



The bones of the hand, 

 twenty -seven in number, may 

 be conveniently divided into 

 three groups : 



(1) The bones of the wrist or 

 carpus eight in number. 



(2) The bones of the palm or 

 metacarpus five in number. 



(3) The bones of the fingers 

 and thumb or phalanges -four- 

 teen in number. 



The Carpus. 



The ossa carpi (carpal bones) 

 are arranged in two rows : the 

 first, or proximal row, comprises 

 from radial to ulnar side, the navi- 

 cular (O.T. scaphoid), os lunatum 

 (O.T. semi-lunar), os triquetrum 

 (O.T. cuneiform), and os pisiforme 

 or pisiform ; the second or distal 

 row includes the greater mult- 

 angular (O.T. trapezium), lesser 

 multangular (O.T. trapezoid), os 

 capitatum (O.T. os magnum), and 



OS HAMATUM 



OS TRIQUETRUM 



PISIFORM 



V. METACARPAL 



FIG. 209. THE BONES OF THE RIGHT WRIST AND HAND 



SEEN FROM THE VOLAR ASPECT. 



