CHAP. IV. IN ANIMALS. 87 admitted that the voice is affected, through, this law; but the explanation appears to me too general and vague to throw much light on the various differences, with the exception of that of loudness, between ordinary speech and emotional speech, or singing. This remark holds good, whether we believe that the various qualities of the voice originated in speaking under the excitement of strong feelings, and that these qualities have subsequently been transferred to vocal music; or whether we believe, as I maintain, that the habit of uttering musical sounds was first developed, as a means of courtship, in the early progenitors of man, and thus became associated with the strongest emotions of which they were capable,ónamely, ardent love, rival- ry and triumph. That animals utter musical notes is familiar to every one, as we may daily hear in the sing- ing of birds. It is a more remarkable fact that an ape, one of the Gibbons, produces an exact octave of musical sounds, ascending and descending the scale by half- tones; so that this monkey " alone of brute mammals may be said to sing.1'3 From this fact, and from the analogy of other animals, I have been led to infer that the progenitors of man probably uttered musical tones, before they had acquired the power of articulate speech; and that consequently, when the voice is used under any strong emotion, it tends to assume, through the prin- ciple of association, a musical character. "We can- plainly perceive, with some of the lower animals, that the males employ their voices to please the females, and that they 8 ' The Descent of Man,' 1870, vol. ii. p. 332. The words quoted are from Professor Owen. It has lately been shown that some quadrupeds much lower in the scale than mon- keys, namely Rodents, are able to produce correct musical tones: see the account'of a singing* Hesperomys, by the Hev. S. Lockwood, in the * American Naturalist,' vol. v. December, 1871, p. 761.