514 THE AMERICAN NATURALIST [Vor. XXXVI. 
MUSCLES. 
As in the normal fore paw, the muscles extensor carpi radi- 
alis longior and extensor carpi radialis brevior (Figs. 5, 6, 
ext.carp.r.lg. and ext.carp.r.brv.) are inserted on the proximal 
dorsal surface of the second and third (counting from the 
radial side) metacarpal bones respectively. 
Considering the evidence of these two muscles alone, we 
should infer that in the polydactyle paw the radial side is nor- 
mally formed and that the extra digit is external to (on the 
- -|- Li ext.com.dg. --2-- | 
-H -|-|--- ---extmindg. ---- T 
-RE----- eiicasp tinm. o 
ho hr, 
ext.carp.r bro 
DIR uem a extcazp.rdg.----- 





| IV 
A JT 
Fic. 5. Fic. 6 
Fic. s.— Dorsal aspect of left manus of normal cat, showing dissection of muscles. ext.carf.r. 
. extensor carpi ialis brevior; ext.carp.rig., extensor carpi radialis longior; 
igitorum ; ex. 
radial 
ext.carp.uin., extensor carpi ulnaris; ext.com.dg., extensor communis 
min.dg., extensor minimi digiti. 
Fic. 6. — Dorsal aspect of left manus of polydactyle cat, showing dissections of same muscles 
ulnar side of) the third one, for in the polydactyle paw there 
are three digits external to the insertion of the extensor carpt 
radialis brevior, whereas in the normal paw there are only 

