SIGNIFICANCE OF PREHALLUX AND TREPOLLEX. 31 



THE PHALANGEAL AFFINITIES OF THE FIRST 

 " METACARPAL " AND " METATARSAL." 



In the ontogeny of the human metacarpus and metatarsus, 

 it is found that each bone arises from two centres, a primary 

 and a secondary. From the first develops the corpus or body 

 of the bone, while from the second arises the epiphysis. In 

 regard to the second-fifth metacarpals and metatarsals, the 

 epiphysis is situated clistally, but in the case of the first meta- 

 carpal and metatarsal the epiphysis is proximal — a feature 

 characteristic of the phalanges. In addition to the method of 

 ossification there is the nature of the vascular supply. The 

 nutrient canal in both the phalanges and the first metacarpal 

 and metatarsal is directed towards the capitulum or " runs 

 from the elbow"; this is the reverse of that which occurs in 

 the remaining metacarpals and metatarsals. 



After taking everything into consideration, the " meta- 

 carpal " and " metatarsal " of the thumb and big toe, respec- 

 tively, show such convincing phalangeal affinities that they ar© 

 now almost universally regarded by anatomists as being 

 homologous with phalanges, but on account of their analogy 

 with the series associated with them, as well as for convenience, 

 their names have not been changed. 



The theories relating to the subject may be grouped under 

 three headings as follows : — 



(a) Three phalanges present, metacarpal (or metatarsal) 



absent ; 

 (6) Two phalanges present, metacarpal (or metatarsal) 



present ; 

 (c) Two phalanges present, proximal component a 

 phalango-metacarpal (or phalango- metatarsal). 

 Of these the first is the most generally accepted and it is the 

 one supported by the authors. With reference to (6) and (c), 

 G. M. Humphrey, in 1858, jDractically combined these two 

 views, as he regarded the bone in the hand articulating with 

 the multangulum majus (trapezius) as intermediate between 

 a phalanx and a metacarpal, but on the whole he considered 

 that it showed more affinities with the latter ; furthermore he 

 was of the opinion that the missing phalanx is the second. 



Wood- Jones (1920) favours the theory of regarding the 

 first element of the first digit as the metacarpal or metatarsal, 

 the second as the first phalanx, and the third as the fused second 

 and third phalanges. 



