slightly upward in its socket affects also the direction of regard in
the open eye by attracting toward itself its plane of vision. But if,
as has been pointed out, this elevation of the line of sight in the
closed eye is accompanied by a characteristic change in the process of
binocular convergence, the result cannot be interpreted as a simple
sympathetic response in the open eye to changes taking place in that
which is closed, but is the consequence of a release of convergence
strain secondarily due to this act of closing the eye.

Several points of comparison between judgments made with binocular and
with monocular vision remain to be stated. In general, the process of
location is more uncertain when one eye only is used than when both
are employed, but this loss in accuracy is very slight and in many
cases disappears. The loss in accuracy is perhaps also indicated by
the range of variation in the two cases, its limits being for
binocular vision +46'.29 to -56'.70, and for monocular +62'.30 to
-61'.10, an increase of 20'.41. In the darkened room similar relations
are presented. The mean variations are as follows: binocular vision,
31'.42; monocular, 32'.17. Its limits in individual judgments are:
binocular, -1'.62 to -128'.70, monocular, +66'.38 to -71'.06, an
increase of 10'.36. In all ways, then, the difference in accuracy
between the two forms of judgment is extremely small, and the
conclusion may be drawn that those significant factors of judgment
which are independent of the figuration of the visual field are not
connected with the stereoscopic functioning of the two eyes, but such
as are afforded by adjustment in the single eye and its results.


VI.