animals call for their mothers. When a flock of sheep is scattered, the
ewes bleat incessantly for their lambs, and their mutual pleasure at
coming together is manifest. Woe betide the man who meddles with the
young of the larger and fiercer quadrupeds, if they hear the cry of
distress from their young. Rage leads to the violent exertion of all
the muscles, including those of the voice; and some animals, when
enraged, endeavour to strike terror into their enemies by its power and
harshness, as the lion does by roaring, and the dog by growling. I
infer that their object is to strike terror, because the lion at the
same time erects the hair of its mane, and the dog the hair along its
back, and thus they make themselves appear as large and terrible as
possible. Rival males try to excel and challenge each other by their
voices, and this leads to deadly contests. Thus the use of the voice
will have become associated with the emotion of anger, however it may
be aroused. We have also seen that intense pain, like rage, leads to
violent outcries, and the exertion of screaming by itself gives some
relief; and thus the use of the voice will have become associated with
suffering of any kind.
The cause of widely different sounds being uttered under different
emotions and sensations is a very obscure subject. Nor does the rule
always hold good that there is any marked difference. For instance with
the dog, the bark of anger and that of joy do not differ much, though
they can be distinguished. It is not probable that any precise
explanation of the cause or source of each particular sound, under
different states of the mind, will ever be given. We know that some
animals, after being domesticated, have acquired the habit of uttering
sounds which were not natural to them.[401] Thus domestic 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 America, which is said to bark. Some breeds, also, of the
domestic pigeon have learnt to coo in a new and quite peculiar manner.
The character of the human voice, under the influence of various
emotions, has been discussed by Mr. Herbert Spencer[402] 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
resonance and _timbre_, in pitch and intervals. No one can listen to an
eloquent orator or preacher, or to a man calling angrily to another, or
to one expressing astonishment, without being struck with the truth of
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