The Madisonian. [volume] (Washington City [i.e. Washington, D.C.]) 1837-1845, 1838-10-17

.Ne,r Points in the Theory of Hision.-At
the eighth meeting Of the British Association
for the advancement Of Science, communi-
cation was made by Sir David Brewster,
On some Preparations Of the Eye" by Will
liam C. Wallace, an Oculist of New York.
As no paper accompanied these preparations,
Sir David Brewster explained to the meeting
their general nature, and their importance in
the establishment Of some interesting points
in the theory fvision. We extract from the
London Atheneum an abstract Of his remarks:
"Mr. Wallace, he stated, considers that he
has discovered the apparatus by which the eye
is adjusted to different distances. This adj
justment is, he conceives effected in two ways
in eyes which have spherical lences it is
produced by falciform, or hook-shaped mus
Gle attached only to one side of the lens,.
which by its construction brings the crystal
line lens nearer the retina. In this case, it is
obvious that the lens will have a slight mo-
ton of rotation, and that the diameter, which
was in the axis Of vision previous to the con-
traction of the muscle, will be moved out OF
that axis after the adjustment, so that at diff
ferent distances Of the lens from the retina
different diameters of it will be placed in the.
axis Of vision. As the dameters of sphere
are all equal and similar, Mr.. Wallace con-
sdered that vision would be equally perfect
along the different diameters Of the lens,
brought by rotation into the axis Of vision.
Sir David Brewster, however, remarked that
he had never found among his numerous ex-
aminations Of the lenses Of fishes any which
are perfectly spherical, as they were all either
oblate or probate speriods, so that along the
different diameters Of the solid lens the vision
would not be similarly performed. But, indie
pendent Of this circumstance, he stated that
in every solid lens there was only one line or
axis in which vision could be perfectly distinct.
namely, the axis Of the optical figure, or se-
ries of positive and Negative luminous sectors,
which are seen by the analysis Of polarized
light. Along every other diameter the optical
action of the lens is not symmetrical When
the lens is not sphere, but ienticular, as in
the human eye or in the eyes of most quadru-
peds, Mr.. Wallace considers that the appara-
tus for adjustment is the ciliary processes, to
which this office had been previously ascribed,
though not on the same scientific grounds as
those discovered by Mr.. Wallace. One Of the
most important results Of Mr.. Wallace's dis
sections is the discovery Of flores in The retina.
These 6bres may be rendered distinctly visi-
bic. They diverge from the base Of the optic
nerve, and surround the .foramen ouale Of
Soemmering at the extremity ofthe eye. Sir
John Hersche had supposed such fbres to be
requisite in the explanation Of his theory Of
vision, and il is therefore doubly interesting to
find that they have actually been discovered.
Sir David Brewster concluded his observa-
tons by expressing hope that anatomists in
this country would turn their attention to this
subject; and that with this view he would
place the preparations Of Mr.. Wallace in the
Exhibition Rooms at Newcastle during the
week."