chap, xv.] THE WRIST AND HAND. 255 



broken in the usual position of a Colles' fracture, but 

 the lower fragment was carried forwards instead of 

 backwards. According to R. W. Smith and others, 

 the peculiar deformity is produced by muscular action, 

 principally by the supinator longus, the extensors of 

 the thumb, and the radial extensors. Lecomte and 

 many French writers assert that the fracture is due 

 to a tearing (arrachement) of the bone by strain upon 

 the ligaments of the wrist. Thus they assert that in 

 forcible extension of the hand the carpal condyle is 

 thrust against the anterior wrist ligaments ; these are 

 intensely stretched, and tear off the lower end of the 

 radius, fracturing it through what is acknowledged to 

 be the weakest part of the bone. It is true that in 

 young subjects the lower epiphysis of the radius can 

 be separated in the cadaver by very forcible flexion or 

 extension of the wrist (B. Anger). This epiphysis is 

 often separated by accidental violence. It joins the 

 shaft about the twentieth year. Its junction with 

 the shaft is represented by a nearly horizontal line, 

 and the epiphysis includes the facet for the ulna 

 and the insertion of the supinator longus. Fractures 

 of the lower end of the radius, due to direct 

 violence, are usually associated with but trifling dis- 

 placement. 



There is no special anatomical interest attach- 

 ing to fractures of the carpus, metacarpus, or pha- 

 langes. 



Dislocations. (1) At the wrist joint. So 

 strong is this articulation, for the reasons above 

 given (page 251), that carpo- radial luxations are ex- 

 tremely rare. For the same reasons, when they do occur 

 they are usually complicated, and are associated 

 with tearing of the skin, or rupture of tendons, 

 or fractures of the adjacent bones. The luxations 

 of the carpus may be either backwards or for- 

 wards, the latter being extremely rare. They 



