258 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Digital variations are extremely rare in the manus of the dog. The 
pes, however, is quite often affected, and in the larger breeds (St. Bernard, 
mastiff, and collie) the hallux is frequently present. All of the digital 
variations which have come under my observation were of the pes. As 
we have seen, this consists of four digits, the hallux being normally 
represented by only the proximal end of its metatarsal bone. The four 
functional digits remain unmodified in all cases of polydactylism, and 
the supernumerary digits occur on the radial side of digit 1, as varia- 
tions of the hallux. We may distinguish three classes of tliese ab- 
normalities: (1) Hallux, or “ dew-claw,” present and formed of two 
phalanges articulating with the distal end of a rudimentary metatarsal. 
This digit does not articulate with the proximal rudiment of meta- 
tarsal 1, but is merely held in place by the skin. Six cases were 
observed in the shepherd dog, and five cases in the St. Bernard. 
(2) Hallux (Fig. D). presenting two well developed phalanges, of 
which the proximal articulates with the rudimentary metatarsal bone ; 
this element is much longer than the normal phalanx. ‘Three cases were 
observed in the mastiff, and one case in the Scotch collie. 
(3) Hallux presentas in (1), and more or less completely duplicated, ex- 
hibiting two phalanges and the distal rudiment of a metatarsal. This is 
the common condition in the pes of the St. Bernard dog. The duplica- 
tion of the hallux may give rise to the rudiment of only a single ungual 
phalanx, or there may be complete duplication, with the formation of 
two similar digits (Fig. #. 1%, 1°). In some cases the two ungual pha- 
langes of 1* and 1 bear but a single large claw, which, however, usually 
shows evidence of duplication. 
The cases of polydactylism which we have observed in Carnivora may 
all be accounted for as modifications of the pollex and hallux. Except 
for the change in symmetry of the phalanges of the extremities of the 
cat, the rest of the manus or pes is unmodified. The conditions found 
in the manus of Carnivora are thus similar to the digital variations 
which occur in the hand of man. In each case a functional, but reduced, 
digit is affected. In man, however, it is the minimus which is normally 
reduced, whereas in Carnivora it is the pollex. 
In the pes of Carnivora the conditions are somewhat different. Only 
a vestige of the hallux is normally present ; in cases of polydactylism, 
this is developed and duplicated to a greater or less degree. It would 
seem, however, that the same underlying cause which produces poly- 
dactylism in the manus (variation of a reduced but functional digit), 
brings about also the digital abnormalities in the pes (variation of a 
—  — a 
