32 PROCEEDINGS OP THE ROYAL SOCIETY OF QUEENSLAND. 



The validity of the epiphyseal argument has been ques- 

 tioned by Allen Thomson (1868, pp. 133-144), who pointed out 

 that the absence of a distal epiphysis in the first ' ' metacarpal ' ' 

 and " metatarsal " is not constant, as there is an occasional 

 ajjpearance of an accessory distal epiphysis in both these bones 

 in man, and to a lesser degree accessory epiphyses may be 

 present in the remaining metacarpals and metatarsals. Thom- 

 son showed that these accessory epiphyses are normal in some 

 animals, and are much better developed than in the case of 

 man, viz. : — 



(a) Distal and proximal epiphyses to all metacarpals 



and metatarsals, e.g. Ornithorynchus ; 



(b) Distal and proximal epiphyses in metatarsals, e.g. 



seal ; 



(c) Distal and proximal epiphyses to first metacarpal 



and metatarsal, e.g. koala ; 



(d) Distal and proximal epiphyses to first metacarpal 



and metatarsal as an occasional variation, e.g. man. 

 Thomson summarised the position in a footnote (ibid., 

 p. 143) as follows : — " These observations are interesting when 

 taken along with those that I have recorded on the seal, as 

 confirming the view of the inconstancy of the absence of a 

 distal epiphysis in the first metacarpal or metatarsal bone, and 

 in showing that we must distrust the position of the epiphyses 

 to these bones as the ground of a homological distinction." 



Even after rejecting the epiphyseal argument as invalid, 

 in view of Thomson's statements, the nutrient canal has still 

 to be explained. In tliis worker's paper (ibid., p. 144, fig. 2-4) 

 these are figured antero-posterior longitudinal sections of the 

 first and second digits of the hand and foot of a child seven 

 years of age. Each of the metacarpals and metatarsals possesses 

 both proximal and distal epiphyses, but in regard to the 

 nutrient foramina the direction of the canal — as indicated by 

 bristles— in the first metacarpal and metatarsal is normal, i.e. 

 towards the head of the bone in the typical phalangeal manner ; 

 in the case of the other two bones, the direction of the canal 

 conforms to the true metacarpal and metatarsal type. 



Broome (Anat. Anz. 28) favours the view that the proximal 

 position of the epiphysis in the first metacarpal is correlated 

 with the great mobihty of the first carpo-metacarpal articula- 

 tion, i.e. the resemblance to the phalanges is due to con- 

 vergence. 



