e phacueidoscope, that accommodation depends on change of form of
the crystalline lens. Where the crystalline is wanting, as Mr. Ware long
ago taught, no power of accommodation remains. The ciliary muscle is
generally thought to effect the change of form of the crystalline. The
power of accommodation is lost after the application of atropine, in
consequence, as is supposed, of the paralysis of this muscle. This, I
believe, is the nearest approach to a demonstration we have on this
point.

I have only time briefly to refer to Professor Draper's most ingenious
theory as to the photographic nature of vision, for an account of which I
must refer to his original and interesting Treatise on Physiology.

It were to be wished that the elaborate and very interesting researches
of the Marquis Corti, which have revealed such singular complexity of
structure in the cochlea of the ear, had done more to clear up its
doubtful physiology; but I am afraid we have nothing but hypotheses for
the special part it plays in the act of hearing, and that we must say the
same respecting the office of the semicircular canals.

The microscope has achieved some of its greatest triumphs in teaching us
the changes which occur in the development of the embryo. No more
interesting discovery stands recorded in the voluminous literature of
this subject than the one originally announced by Martin Barry,
afterwards discredited, and still later confirmed by Mr. Newport and
others; namely the fact that the fertilizing filament reaches the
interior of the ovum in various animals;--a striking parallel to the
action of the pollen-tube in the vegetable. But beyond the mechanical
facts all is mystery in the movements of organization, as profound as in
the fall of a stone or the formation of a crystal.

To the chemist and the microscopist the living body presents the same
difficulties, arising from the fact that everything is in perpetual
change in the organism. The fibrine of the blood puzzles the one as much
as its globules puzzle the other. The difference between the branches of
science which deal with space only, and those which deal with space and
time, is this: we have no glasses that can magnify time. The figure I
here show you a was photographed from an object (pleurosigma angulatum)
magnified a thousand diameters, or presenting a million times its natural
surface. This other figure of the same object, enlarged from the one
just shown, is magnified seve