rom year to
year; but a fact once seen, a relation of cause and effect, once
demonstratively apprehended, are possessions which neither change nor
pass away, but, on the contrary, form fixed centres, about which other
truths aggregate by natural affinity.
Therefore, the great business of the scientific teacher is, to imprint
the fundamental, irrefragable facts of his science, not only by words
upon the mind, but by sensible impressions upon the eye, and ear, and
touch of the student, in so complete a manner, that every term used, or
law enunciated, should afterwards call up vivid images of the particular
structural, or other, facts which furnished the demonstration of the
law, or the illustration of the term.
Now this important operation can only be achieved by constant
demonstration, which may take place to a certain imperfect extent during
a lecture, but which ought also to be carried on independently, and
which should be addressed to each individual student, the teacher
endeavouring, not so much to show a thing to the learner, as to make him
see it for himself.
I am well aware that there are great practical difficulties in the way
of effectual zoological demonstrations. The dissection of animals is
not altogether pleasant, and requires much time; nor is it easy to
secure an adequate supply of the needful specimens. The botanist has
here a great advantage; his specimens are easily obtained, are clean and
wholesome, and can be dissected in a private house as well as anywhere
else; and hence, I believe, the fact, that botany is so much more
readily and better taught than its sister science. But, be it difficult
or be it easy, if zoological science is to be properly studied,
demonstration, and, consequently, dissection, must be had. Without it,
no man can have a really sound knowledge of animal organization.
A good deal may be done, however, without actual dissection on the
student's part, by demonstration upon specimens and preparations; and in
all probability it would not be very difficult, were the demand
sufficient, to organize collections of such objects, sufficient for all
the purposes of elementary teaching, at a comparatively cheap rate. Even
without these, much might be effected, if the zoological collections,
which are open to the public, were arranged according to what has been
termed the "typical principle;" that is to say, if the specimens exposed
to public view were so selected, that the public coul
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