the two. The anæsthesia must intervene between the two appearances.
The conjecture of Schwarz, that the fainter streak is but a second
appearance of the stronger, is undoubtedly right.

We know too that the anæsthesia depends on a mechanism central of the
retina, for stimulations are received during movement but not
transmitted to consciousness till afterward. This would be further
shown if it should be found that movements of the head, no less than
those of the eyes, condition the anæsthesia. As before said, it is not
certain that the eyes do not move slightly in the head while the head
moves. The movement of the eyes must then be very slight, and the
anæsthesia correspondingly either brief or discontinuous. Whereas, the
phenomena are the same when the head moves 90° as when the eyes move
that amount. It seems probable, then, that voluntary movements of the
head do equally condition the anæsthesia.

We have seen, too, that in reflex eye-or head-movements no anæsthesia
is so far to be demonstrated. The closeness with which the eye follows
the unexpected gyrations of a slowly waving rush-light, proves that
the reflex movement is produced by a succession of brief impulses
(probably from the cerebellum), each one of which carries the eye
through only a very short distance. It is an interesting question,
whether there is an instant of anæsthesia for each one of these
involuntary innervations--an instant too brief to be revealed by the
experimental conditions employed above. The seeming continuity of the
sensation during reflex movement would of course not argue against
such successive instants of anæsthesia, since no discontinuity of
vision during voluntary movement is noticeable, although a relatively
long moment of anæsthesia actually intervenes.