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same breath that there is a great moral and intellectual chasm between
man and the lower animals。 How is this possible when you declare that
moral and intellectual characteristics depend on structure； and yet
tell us that there is no such gulf between the structure of man and that
of the lower animals？〃
I think that objection is based upon a misconception of the real
relations which exist between structure and function； between mechanism
and work。 Function is the expression of molecular forces and
arrangements no doubt； but； does it follow from this； that variation in
function so depends upon variation in structure that the former is
always exactly proportioned to the latter？ If there is no such
relation； if the variation in function which follows on a variation in
structure； may be enormously greater than the variation of the
structure； then； you see； the objection falls to the ground。
Take a couple of watchesmade by the same maker； and as completely
alike as possible； set them upon the table； and the function of
eachwhich is its rate of goingwill be performed in the same manner；
and you shall be able to distinguish no difference between them； but let
me take a pair of pincers； and if my hand is steady enough to do it；
let me just lightly crush together the bearings of the balance…wheel；
or force to a slightly different angle the teeth of the escapement of
one of them； and of course you know the immediate result will be that
the watch； so treated； from that moment will cease to go。 But what
proportion is there between the structural alteration and the
functional result？ Is it not perfectly obvious that the alteration is
of the minutest kind； yet that slight as it is； it has produced an
infinite difference in the performance of the functions of these two
instruments？
Well； now； apply that to the present question。 What is it that
constitutes and makes man what he is？ What is it but his power of
languagethat language giving him the means of recording his
experiencemaking every generation somewhat wiser than its
predecessor；more in accordance with the established order of the
universe？
What is it but this power of speech； of recording experience； which
enables men to be menlooking before and after and； in some dim sense；
understanding the working of this wondrous universeand which
distinguishes man from the whole of the brute world？ I say that this
functional difference is vast； unfathomable； and truly infinite in its
consequences； and I say at the same time； that it may depend upon
structural differences which shall be absolutely inappreciable to us
with our present means of investigation。 What is this very speech that
we are talking about？ I am speaking to you at this moment； but if you
were to alter； in the minutest degree； the proportion of the nervous
forces now active in the two nerves which supply the muscles of my
glottis； I should become suddenly dumb。 The voice is produced only so
long as the vocal chords are parallel； and these are parallel only so
long as certain muscles contract with exact equality； and that again
depends on the equality of action of those two nerves I spoke of。 So
that a change of the minutest kind in the structure of one of these
nerves； or in the structure of the part in which it originates； or of
the supply of blood to that part； or of one of the muscles to which it
is distributed； might render all of us dumb。 But a race of dumb men；
deprived of all communication with those who could speak； would be
little indeed removed from the brutes。 And the moral and intellectual
difference between them and ourselves would be practically infinite；
though the naturalist should not be able to find a single shadow of
even specific structural difference。
But let me dismiss this question now； and； in conclusion； let me say
that you may go away with it as my mature conviction； that Mr。 Darwin's
work is the greatest contribution which has been made to biological
science since the publication of the 'Regne Animal' of Cuvier； and
since that of the 'History of Development' of Von Baer。 I believe that
if you strip it of its theoretical part it still remains one of the
greatest encyclopaedias of biological doctrine that any one man ever
brought forth； and I believe that； if you take it as the embodiment of
an hypothesis； it is destined to be the guide of biological and
psychological speculation for the next three or four generations。
End