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FIRST CLASS OF OBJECTS FOR THE SUBJECT. 79
a distant surface, with which I necessarily identify it as
"belonging to its effect, the cross will occupy 2 of a distant
and therefore larger sphere, and is consequently large.
If, on the other hand, I project the image on to a nearer
object, it will occupy 2 of a smaller sphere, and is
therefore small. The resulting perception is in both cases
completely objective, quite like that of an external object ;
and as it proceeds from an entirely subjective reason
(from the image having been excited in quite
way),
a different
it thus confirms the intellectual character of all
objective perception. This phenomenon (which I dis
tinctly remember to have been the first to notice, in
1815) forms the theme of an essay by Seguin, published in
"
the
of the 2nd August, 1858, where it
Comptes rendus
"
is served up as a new discovery, all sorts of absurd and
distorted explanations of it being given. Messieurs les
illustres confreres let pass no opportunity for heaping ex
periment upon experiment, the more complicated the
better. Experience! is their watchword; yet how rarely
do we meet with any sound, genuine reflection upon the
phenomena observed! Experience! experience! followed
by twaddle.
To return to the subsidiary data which act as com
mentaries to a given visual angle, we find foremost among
them the mutationes oculi internee, by means of which the
eye adapts its refractory apparatus to various distances by
increasing and diminishing the refraction. In what these
modifications consist, has not yet been clearly ascertained.
They have been sought in the increased convexity, now of
the cornea, now of the crystalline lens; but the latest
theory seems to me the most probable one, according to
which the lens is moved backwards for distant vision and
forwards for near vision, lateral pressure, in the latter
case, giving it increased protuberance ;
so that the process
would exactly resemble the mechanism of an opera-glass.