360 MERISTIC VARIATION. [part i. 



Reduction of digit IV of pes. 

 *531. [This case is introduced here for comparison with the last.] A left foot having 

 abnormalities as follows. Calcaneum, astragalus, internal cuneiform normal in size 

 and shape. The second cuneiform is rather broader than usual, but the surface 

 which it presents to the internal cuneiform has all the characters of a middle cunei- 

 form. External to this middle cuneiform is only one large tarsal bone in the distal 

 row. This bone presents no clear sign of duplicity, but from its form and relations 

 it appeared that it represented both the cuboid and the ecto-cuneiform. The hallux 

 and digit II have approximately normal relations. The large cuboid-like bone 

 bears externally a metatarsal agreeing in shape with a metatarsal V ; and internal 

 to this the same tarsal bone bears another metatarsal which upon its external side 

 gives off yet another metatarsal of reduced size. Each of the five metatarsals bore 

 a digit, but the digits of the minimus and of the slender IV were webbed together. 

 [Full details given.] Beennek, A., Virch. Arch. f. path. Anat. u. Phys., 1883, xciv. 

 p. 23, PI. ii. 



532. Besides these simpler cases there are very many recorded instances of reduction 

 in number of digits in which the identification of the parts is quite uncertain. From 

 the point of view of the naturalist it is worthy of remark that even in some of the 

 cases departing most widely from the normal form the limb though having only 

 three or perhaps two digits still preseuts an approach to a symmetry. Examples of 

 this kind are given by Guyot-Daubes (Rev. d'Anthropol., 1888, xvn. p. 541, figs.) 

 and by Fotherby (Brit. Med. Jour., 1886 (1), p. 975 figs. ) and many more. Fotherby's 

 record is interesting as relating to a family among whose members feet bearing only 

 two opposable claw-like digits of irregular form recurred for five generations. Evi- 

 dence relating to limbs of this kind is so obscure that it is not possible as yet to make 

 deductions from it, but there seems to be a general agreement among anatomists 

 that when two digits only remain one of them has the characters of a minimus. 



Reference must be made also to the fact that in cases of absence of radius the 

 pollex is almost always absent. This seems to be established in very many cases. 

 The only examples of a pollex present in the absence of a radius known to me are 

 that of Gruber, Virch. Arch. f. path. Anat. u. Phys. 1865, xxxn. p. 211, and that of 

 Geissendorfer, Zur Casuistik d. congen. Radiusdefectes, Munch. 1890. 



Horse. 



Variation in the number of digits in the Horse 1 has been 

 repeatedly observed from the earliest times. The mode of occur- 

 rence of the change is by no means always the same, but on the 

 contrary several distinct forms of Variation may be recognized. 

 On inspection the cases may be divided into two groups. 



A. Cases in which the extra digit (or digits) possesses a distinct 

 metacarpal or metatarsal. 



B. Cases in which the large metacarpal or metatarsal (III) gives 

 articulation to more than one digit. 



Besides these I have placed together in a third group (C) two 

 very remarkable cases which cannot be clearly assigned to either of 

 the other groups. These instances are of exceptional interest from 

 the fact that in them is exhibited a condition intermediate between 

 those of the other two groups. We have seen repeatedly that 



1 In the Mule two cases have been recorded, but in the Ass I know no instance 

 of polydactylism. Describing a polydactyle horse seen on a journey in Rio Grande 

 von Jhering (Kosmos, 1884, xiv. p. 99) states that he believes polydactyle horses to 

 be much more common in S. America than in Europe, and that most persons who 

 have travelled much in that country have met with cases. Mules between the 

 jackass and mare are bred in great numbers, but he had heard of no case in a mule. 



