this illusion. As in the case of the illusion for passive touch, there
are not wanting champions of both opinions as to the direction in
which this illusion lies.

I may say in advance of the account of my experiments, that I have
here also found a ground of reconciliation for these two divergent
opinions. Just as in the case of the illusion for passive touch, there
are here also certain conditions under which the filled space seems
longer, and other conditions under which it appears shorter than the
open space. I feel warranted, therefore, in giving in some detail my
research on this illusion, which again has been an extended one. I
think that the results of this study are equally important with those
for passive touch, because of the further light which they throw on
the way in which our touch sense functions in the perception of the
geometrical illusions. Dresslar's experiments, like those of James,
were made with cards in which one half was filled with punctures. The
number of punctures in each centimeter varied with the different
cards. Dresslar's conclusion was not only that the filled space is
overestimated, but also that the overestimation varies, in a general
way, with the number of punctures in the filling. Up to a certain
point, the more holes there are in the card, the longer the space
appears.

I had at the onset of the present experiment the same feeling about
Dresslar's work that I had about Parrish's work, which I have already
criticised, namely, that a large number of experiments, in which many
variations were introduced, would bring to light facts that would
explain the variety of opinion that had hitherto been expressed. I was
confident, however, that what was most needed was a quantitative
determination of the illusion. Then, too, inasmuch as the illusion,