and especially, whether the same general principles can be applied
with satisfactory results, both to man and the lower animals.
This latter method, I am inclined to think, is the most serviceable of all.
The difficulty of judging of the truth of any theoretical explanation,
and of testing it by some distinct line of investigation, is the great
drawback to that interest which the study seems well fitted to excite.

Finally, with respect to my own observations, I may state that they
were commenced in the year 1838; and from that time to the present day,
I have occasionally attended to the subject. At the above date,
I was already inclined to believe in the principle of evolution,
or of the derivation of species from other and lower forms.
Consequently, when I read Sir C. Bell's great work, his view,
that man had been created with certain muscles specially adapted
for the expression of his feelings, struck me as unsatisfactory.
It seemed probable that the habit of expressing our feelings
by certain movements, though now rendered innate, had been
in some manner gradually acquired. But to discover how such
habits had been acquired was perplexing in no small degree.
The whole subject had to be viewed under a new aspect,
and each expression demanded a rational explanation.
This belief led me to attempt the present work, however imperfectly
it may have been executed.--------


I will now give the names of the gentlemen to whom, as I have said,
I am deeply indebted for information in regard to the expressions
exhibited by various races of man, and I will specify some
of the circumstances under which the observations were in each
case made. Owing to the great kindness and powerful influence