B. Another test for this anæsthesia during movement is offered in the
following experiment. It is clear that, just as a light-stimulation is
not perceived if the whole retinal process begins and ends during a
movement, so also a particular phase of it should not be perceived if
that phase can be given complete within the time of the movement. The
same pendulum which was used in the previous experiment makes such a
thing possible. If in place of the perforated dumb-bell the pendulum
exposes two pieces of glass of nearly complementary colors, one after
the other coming opposite the place of exposure, the sensations will
fuse or will not fuse according as the pendulum swings rapidly or
slowly. But now a mean rate of succession can be found such as to let
the first color be seen pure before the second is exposed, and then to
show the second fused with the after-image of the first. Under some
conditions the second will persist after the first has faded, and will
then itself be seen pure. Thus there may be three phases in
consciousness. If the first color exposed is green and the second red,
the phases of sensation will be green, white, and perhaps red. These
phases are felt to be not simultaneous but successive. A modification
of this method is used in the following experiment. (See Fig. 8, Plate
IV.)

_T_ and _I_ here correspond to the cards _T_ and _I_ of Fig. 6.
_T_ consists of a rectangular opening, 9×5 cm., which contains three
pieces of glass, two pieces of green at the ends, each 2.8 cm. wide
and 7 cm. high, and a piece of red glass in the middle 3.4 cm. wide
and only 1.5 cm. high, the space above and below this width being
filled with opaque material. The shape of the image is determined as
before by the hole in _I_, which now, instead of being a dumb-bell, is
merely a rectangular hole 2 cm. wide and 5 cm. high. Exactly as
before, _T_ is fixed in the background and _I_ swings with the