132 SPECIAL EXPRESSIONS: CIIAP. V. Young Orangs, when tickled, likewise grin and make a chuckling sound; and Mr. Martin says that their eyes grow brighter. As soon as their laughter ceases, an ex- pression may be detected passing over their faces, which, as Mr. Wallace remarked to me, may he called a smile. I have also noticed something of the same kind with the chimpanzee. Dr. Duchenne—and I cannot quote a better authority—informs me that he kept a very tame monkey in his house for a year; and Avhen he gave it dur- ing meal-times some choice delicacy, he observed that the comers of its mouth were slightly raised; thus an expression of satisfaction, partaking of the nature of an incipient smile, and resembling that often seen on the face of man, could be plainly perceived in this animal.)1 The Oebus azarce^ when rejoided at again seeing a beloved person, utters a peculiar tittering (kiclierndc-n) sound. It also expresses agreeable sensations, by drawing back the corners of its mouth, without producing any sound. Kengger calls this movement laughter, but it would be more appropriately called a smile. The form of the mouth is different when cither pain or terror is expressed, and high shrieks are uttered. Another spe- cies of Cebus in the Zoological Gardens (0. liypoleucus) when pleased, makes a reiterated shrill note, and likewise draws back the corners of its mouth, apparently through the contraction of the same muscles as with us. So does the Barbary ape (Inuus ecaudatus) to an extraordinary degree; and I observed in this monkey that the skin of the lower eyelids then became much wrinkled. At the same time it rapidly moved its lower jaw or lips in a spasmodic manner, the teeth being exposed; but the noise produced was hardly more distinct than that which 11 !Rengger (' Smigetheire von Paraqviny', 1830, s. 46) kept these monkeys in confinement for seven, years in their native country of Paraguay.