in extreme cases. Differences in quality are also
excluded, for the tactual sensation has probably
the same quality everywhere on the skin, and tem-
perature sensations, which may certainly be ob-
tained in different regions with identical quality,
are also localized.

The fact that localization does not depend on
quality is more apparent in the case of the eye.
Stimulations of different points of the retina (if not
too close together) are always discriminated as dif-
ferent, and by habitual association referred to the
relative angular positions from which the stimulat-
ing rays of light must come. The discrimination
of positions in the visual field depends, in short, on
the discrimination of positions on the retina. And
though the hue of a color roused by a given light
stimulus varies according to the part of the retina
stimulated, there are many different points in the
retina giving the same qualitative mixture, which
are, nevertheless, discriminated. The hues, more-
over, may be varied through the whole range of the
spectrum without affecting the locality discrimina-
tion; the discrimination, therefore, cannot depend
on quality.

The character of sensation which furnishes the
real basis for localization is thus demonstrable only

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