have subjected it
compel me accept the result as final.

[Sidenote: SIGN COMMON TO MAN AND SIMIAN]

A little more than a year ago, my attention was called to this sign by
the children who own the little Capuchin, Jack, in Charlestown. A number
of times they said to him in my presence, "Jack, you must go to bed." At
which he would shake his little black head, as if he really did not wish
to comply. I watched this with great interest; but it was my belief at
that time that he had been trained to do this, and that the sign did not
really signify to him anything at all. The children, however, declared
to me that he really meant "no." To believe that he meant this would
presuppose that he understood the combination of words quoted; and this
was beyond the limits of my faith, although it was certain that a
repetition of the sentence always elicited from him the same sign,
which indicated that he recognised it as the same sentence or
combination of sounds, and gave it the same reply each time. I concluded
that he had been taught to associate this sign with some sound--for
instance, "bed" or "go"; but since that time I have found the sign to be
almost universal with this species of monkey, and they use the sign to
express negation. I have seen them use the sign in response to certain
things which were wholly new to them, but where the idea was clear to
them and they desired to express dissent. The fact that this sign is
common to both man and Simian, I regard as more than a mere coincidence;
and I believe that in this sign I have found the psycho-physical basis
of expression.

I have made scores of experiments on this subject, and I find this sign
a fixed factor of expression. In one case, where I tried to induce a
monkey to allow me to take him into my hands from the hand of his
master, he would shake his head each time, and make a peculiar sound
somewhat like a suppressed cluck. I would try to coax him with nuts, in
response to which he would make the same sound and sign each time, and
his actions showed beyond all controversy his intention. I had taught a
monkey to drink milk from a bottle by sucking it through a rubber
nipple, and after he had satisfied his thirst, when I would try to force
the bottle to his lips, he would invariably respond by a shake of the
head in the manner described, and at the same time utter a clucking
sound. I tried many similar experiments with three or four other
monkeys, and secured the same