326 .M HRISTIC VARIATION. [PART I. 



In addition to cases more or less conforming to schemes that 

 can be indicated art- several which cannot be thus included. These 

 will be duly noticed \\ln-n the more schematic cases have been 

 described. That any of the cases can be arranged in a formal 

 sequence of this kind is perhaps surprising, and the relations of 

 some nt the < Conditions, II and III fur instance, to each other must 

 at once recall the principle seen already in other examples of 

 addition of a member at the end of a successive series of parts, 

 notably in tin ea>e of Teeth (see p. 272). It was then pointed out 

 that \vheu a new member is added beyond a terminal member 

 whose size is normally small relatively to that of the normal 

 penultimate, then the member whieh is normally terminal is 

 raised to a higher condition. Now this same principle is seen in 

 ( 'oiid it ion III of t lie polydactyle manus. 



Attention must nevertheless be forthwith called to the fact 

 that a t \vo-phalanged digit 1 may be present internal to the thumb 

 (usually arising from it) though the thumb has still but two 

 phalanges. J5ut generally these cases may properly be described 

 as examples of tl/iji/irity of the thumb; and as was well seen in 

 the case of Teeth, any member of a series may divide into two 

 though the rest of the series remain unaltered. Duplicity of a 

 member without reconstitution of the series is to be recognized as 

 one occurrence, and change in number associated with reconstitu- 

 tion of other members especially, of adjacent members, is another. 

 In Teeth and other M eristic series these two phenomena are both 

 to be seen, though as was pointed out (p. 270) they pass insensibly 

 into each other. 



Another feature to be specially mentioned in this preliminary 

 notice is the difference in the manner in which the higher forms 

 of polydactylism appears in the human foot from that seen in the 

 human hand. In the hand there is this strange group of cases 

 forming a progress from the normal hand to Condition V, besides 

 the distinct series of double-hands. Polydactyle feet on the con- 

 trary do not in Man, so far as they have been observed (with the 

 doubtful exception of Nos. 499 and 500), develop a new symmetry. 



CASES OK I'OLYDACTYUSM ASSOCIATED WITH CHANGE OF SYMMETRY. 

 A. l)i<//tx in one Successive Series. 



*481. Man having a "supernumerary index" on each hand. Left 

 hand. No " thumb" present. In its stead there is a digit having 

 three phalanges whieh "performs its oth'ce." The middle phalanx 

 was abnormally short. The first intermetacarpal space was not 

 great. [Degree of opposability not stated.] Right hand. In 

 addition to four normal lingers there was a three-jointed digit 



1 A case in which a .'l-phubniLvd ili^it was placed on the radial side of the pollex 

 is mentioned by WINMJ:, Jam-. Aunt. J'lii/*.. xxvi. p. MO, but has not yet been 

 described. No other such case is known to me. This perhaps should be classed 

 with double-hands. Cp. No. 502. 



