chap, xiil] DIGITS : MAN. 345 



These general phenomena of polydactylism have been observed 

 from the earliest times and the literature relating to the subject 

 is of great extent. Most cases known up to 1869 [not including 

 Struthers' cases] were collected by Fort, Difformites des Doigts, 

 Paris, 1869, and independently by Grubeu, Bull. Ac. Sci. Pet, 

 xv. 1871, p. 352 and p. 460, and good collections of references have 

 subsequently been published, especially by Fackexheim. Jen. 

 Zeits., XXII. p. 343. Of the whole number of cases the majority 

 fall into a few types, and a great part of the evidence may thus be 

 easily summarized and illustrated by specimen-cases. The forms 

 of polydactylism thus constantly recurring may be dealt with 

 conveniently under the following heads. 



(1) Addition of a single digit, complete or incomplete. 



A. external to minimus, in series with the other digits. 



B. in other positions. 



(2) Duplication of single digits, especially of the pollex and 



hallux. 



(3) Combinations of the foregoing. 



Besides these are a certain number of cases not included in 

 the above descriptions, and of them an account will be given under 

 the heading 



(4) Irregular examples. 



As bearing upon the frequency of the several forms of poly- 

 dactylism it may be stated that in this irregular group are 

 included all cases which I have met with that exhibit any feature 

 of importance in departure from the cases otherwise cited. For 

 the purpose of this list I have examined every record of polydactyl- 

 ism to which access could be obtained. 



(1) A. Single extra digit external to minimus in hand or foot. 



(a) Incomplete form. 



This is one of the commonest forms of extra digit. In the great 

 majority of such cases the extra digit is not complete from the carpus 

 or tarsus but arises from the metacarpal or metatarsal, less often from 

 one of the phalanges, of the minimus. The attachment may be either 

 by a direct articulation upon the side of one of these bones, or they may 

 give off a branch bearing the extra digit. In a not uncommon form 

 of the variation the extra digit has no bony attachment to the hand, 

 but is a rudimentary structure hanging from some part of the minimus 

 by a peduncle. Of these several forms the following are illustrative 

 cases. 



-A' Extra digit hanging from minimus hi/ a peduncle. 



Nanus. Annandale", Diseases of Fingers and Toes, 1865, p. 30, PI. n. fig. 20; 

 Tarnier, Bull. Soc. de Chir., Paris, vi., 1866, p. 487; and numerous other examples. 

 Pes. Bcsch, quoted by Grcber, I.e., p. 470: this form in the pes is rare. 



