of fusion
under ordinary conditions.' But "these failures suggested an increase
of the illumination of the field of exposure.... Under these
conditions a long band of light was immediately evident at each
movement of the eye." This and similar observations were believed 'to
show experimentally that when a complex field of vision is perceived
during eye-movement it is seen fused' (p. 462).

[18] Dodge, PSYCHOLOGICAL REVIEW, 1900, VII., p. 459.

Between the 'failures' and the cases when a band of light was seen, no
change in the conditions had been introduced except 'an increase of
the illumination.' Suppose now this change made just the difference
between a stimulation which left _no_ appreciable _after-image_, and
one which left _a distinct one_. And is it even possible, in view of
the extreme rapidity of eye-movements, that a retinal stimulation of
any considerable intensity should not endure after the movement, to be
_then_ perceived, whether or not it had been first 'perceived during
the movement'?

Both of Dodge's experiments are open to the same objection. They do
not admit of distinguishing between consciousness of a retinal process
during the moment of stimulation, and consciousness of the same
process just afterward. In both his cases the stimulation was given
during the eye-movement, but there was nothing to prove that it was
perceived at just the same moment. Whatever the difficulties of
demonstrating an anaesthesia during movement, an experiment which does
not observe the mentioned distinction can never disprove the
hypothesis.

[Illustration: Fig. 2.]

For the sake of a better understanding of these bands of light of
Dodge, a perimeter was equipped in as nearly the manner described by
him (_ibid._, p. 460) as possible. Experiments with the eye moving
past a very narrow illuminated slit confirmed his observations. If the
light behind the slit was feeble, no band was seen; if moderately
bright, a band was always seen. The most striking fact, however, was
that the band was not localized behind the slit, but was projected on
to that point where the eye came to rest. The band seemed to appear
at this point and there to hover until it faded away. This apparent
anomaly of localization, which Dodge does not mention, suggests the
localization which Schwarz describes of his streaks. Hereupon the
apparatus was further modified so that, whereas Dodge had let the
stimulation take place only during the movement