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centre failed on the right foot but the accessory hypothenar was very 
distinct. In twenty-two human feet examined, a well defined thenar 
centre was found in all cases, occupying the large eminence back of 
the hallux. The palmar centres were very varient, the median one 
being usually indicated and the first, or tibial, rarely. 
Summary of results. The definite conclusions which are the 
results of the facts collected in this paper may be stated as follows: 
I. The various callosities which form the pads on 
the feetof walking pentadactylous Mammals become re- 
duced in certain monkeys (ex. Inuus) to fleshy mounds 
without definite boundaries. 
Il Over these mounds the epidermic folds, which 
run elsewhere in approximately parallel, somewhat 
wavy lines, are variously distorted and appear in the 
form of whorls, spirals or loops. 
Ill. In some Primates, including Man, the mounds 
suffer a more or less complete reduction, so that often 
the epidermic figure, or “centre” is alone left to desig- 
nate the spot. In cases of extreme reduction, the epi- 
dermic centre may also disappear. 
IV. In Man the apical centres on the finger tips are 
fairly constant, that form designated by Garon as a 
“simple arch” being the most reduced. The palmar, 
thenar and hypothenar centres are of uncertain occur- 
rence. 
Beyond the conclusions given us by the facts at hand, we are 
tempted to ask questions concerning tle phylogenetic origin of the 
simple epidermic folds, the causes which may have led to the formation 
of the “centres”, which of the patterns is the more primitive and 
their morphological relation to each other. To reply in part to these 
I will offer the following very theoretical sketch to serve as a working 
hypothesis, without wishing thereby to commit myself to the con- 
clusions given. I shall hope soon, however, to supply a few more 
facts to bear upon this portion of the field. 
I. In very primitive Mammals the epidermic ridges may have 
run evenly and in a parallel direction across the volar sur- 
face of the paws (this might suggest the rows of scales of 
WEBER and DE MEIJERE). 
Il. The pressure produced upon certain points by contact with 
the ground resulted in the formation of pads, the convex 
