CHAP. V. MONKEYS. 131 see in the following chapters, the different races of man express their emotions and sensations with remarkable uniformity throughout the world. ...Some of the expres- sive actions of monkeys are interesting in another way, namely from being closely analogous to those of man."1 As I have had no opportunity of observing any one species of the group under all circumstances, my miscellaneous remarks will be best arranged under different states of the mind. Pleasure, joy, affection.—It is not possible to distin- guish in monkeys, at least without more experience than I have had, the expression of pleasure or joy from that of affection. Young chimpanzees make a kind of bark- ing noise, when pleased by the return of anyone to whom they are attached. When this noise, which the keepers call a laugh, is uttered, the lips are protruded; but so they are under various other emotions. Nevertheless I could perceive that when they were pleased the form of the lips differed a little from that assumed when they were angered. If a young chimpanzee be tickled—and the armpi-ts are particularly sensitive to tickling, as in the case of our children,—a more decided chuckling or laughing sound is uttered; though the laughter is some- times noiseless. The corners of the mouth are then drawn backwards; and this sometimes causes the lower eyelids to be slightly wrinkled. But this Avrinkling, which is so characteristic of our own laughter, is more plainly seen in some other monkeys. The teeth in the upper jaw in the chimpanzee are not exposed when they utter their laughing noise, in which respect they differ from us. But their eyes spark]e and grow brighter, 'as Mr. W. L. Martin,10 who has particularly attended to their expression, states.' 10 ' Natural History of Mammalia,' 1841, vol. i. pp. 383, 410.