522 THE AMERICAN NATURALIST. [VoL. XXXVI. 
manus, except that it is somewhat like a pollex, which, when 
retractable, as occasionally happens, is carved away on the 
radial side. 
The ungual phalanges are too nearly alike in the normal and 
the polydactyle paw to be of service as far as our purpose is 
concerned. 
GENERAL CONSIDERATIONS. 
The facts learned from the dissection of the polydactyle 
manus are in part contradictory; that is, some facts suggest 
that the extra digit occurs on the radial side of the paw, 
whereas others indicate an extra digit on the ulnar side; but, 
on the whole, the balance of the evidence points to the exist- 
ence of the extra digit on the radial side of the three ulnar digits. 
The evidence which the bones furnish seems to be the most 
satisfactory, and is borne out in the majority of cases by the 
other tissues. The middle phalanges of digits ///, /V, and 
V (Figs. 17, 18) are carved away on the ulnar side, as nor- 
mally. The middle phalanx of digit C (Fig. 18) is an indif- 
ferent digit, Z.e., carved away on neither side. In this it more 
resembles a pollex than a digit. The middle phalanx of 
digit B (Fig. 18) is carved away on the radial side, in this 
respect resembling a pollex more than a digit. Digits ///, /V, 
and V in both manus are distinctly similar. Regarding the 
articulation of the metacarpals with the carpals, it is seen that 
the five external digits of the abnormal manus have the same 
articulation as do the five digits of the normal manus. The 
pollex of the abnormal manus has the articulation abnormal, in 
that it is with the radial sesamoid, which in this case is fused 
with the scapho-lunar. Here the five digits nearest the ulnar 
side are normal 
Considering the three ulnar digits of the abnormal manus to 
correspond to normal digits, one is naturally led to inquire what 
modifications the manus has undergone that there should be 
three digits instead of two on the radial side of the three ulnar 
normal ones. Further evidence from the bones is interesting 
in respect to this query. 

