86 MEANS OF EXPRESSION CHAP. IV.
will ever be given. We know that some animals, after
being domesticated, have acquired the habit of utter-
ing sounds which were not natural to them.1 Thus do-
mestic dogs, and even tamed jackals, have learnt to bark,
which is a noise not proper to any species of the genus,
with the exception of the Canis latrans of North Ameri-
ca, which is said to bark. Some breeds, also, of the do-
mestic pigeon have learnt to coo in a new and. quite
The character of the human voice, under the influ-
ence of various emotions, has been discussed by Mr. Her-
bert Spencer 2 in his interesting essay on Music. He
clearly shows that the voice alters much under different
conditions, in loudness and in quality, that is,'in reso-
nance and timbre, in pitch and intervals. No one can
listen to an eloquent orator or preacher, or to a man call-
ing angrily to another, or to one expressing astonish-
ment, without being struck with the truth of Mr. Spen-
cer's remarks. It is curious how early in life the modu-
lation of the voice becomes expressive. With one of my
children, under the age of two years, I clearly perceived
that his humph of assent was rendered by a slight modu-
lation strongly emphatic; and that by a peculiar whine
his negative expressed obstinate determination. Mr.
Spencer further shows that emotional speech, in all the
above respects is intimately related to vocal music, and
consequently to instrumental music; and he attempts
to explain the characteristic qualities of both on physio-
logical grounds—namely, on "the general law that a
feeling is a stimulus to muscular action." It may be
1 See the evidence on this head in my ' Variation of
Animals and Plants under Domestication,' vol. i. p. 27.
On the cooing- of pig-eons, vol. i. pp. 154, 155.
2.' Essays, Scientific, Political, and Speculative,' 1858.
* The Origin and Function of Music,' p. 359.