158 ANTHROPOID APES. 



brows which is covered with bristly hairs, and a 

 wrinkling of the skin which covers the, bridge of 

 the nose in the gorilla and the chimpanzee, and 

 have illustrated this expression by a drawing. 



Darwin goes on to say that when a young chim- 

 panzee is tickled, to which, as in the case of children, 

 their armpits are peculiarly sensitive, he generally 

 utters a chuckling or laughing sound, although 

 sometimes the laugh is silent. The corners of the 

 mouth are then drawn back, and this sometimes 

 causes the eyelids to be slightly wrinkled. This 

 wrinkling, which is so characteristic of the human 

 laugh, is still more apparent in some of the other 

 apes. In the chimpanzee the teeth of the upper 

 jaw are not exposed when he utters this laughing 

 sound, and in this respect he differs from man. 

 Darwin further observes that when the tickled 

 young orang ceases to laugh, an expression passes 

 over his face, which, according to Wallace, may be 

 called a smile. Darwin has observed something 

 similar in the chimpanzee.* 



My own observation confirms what has been said 

 of the chuckling of a tickled chimpanzee. When 

 Dr. Hermes, the director of the Berlin Aquarium, 

 played with the chimpanzee which was kept in that 

 establishment, a contortion of the corner of the 

 mouth, resembling a somewhat sardonic smile, at 

 once appeared. No specimen displayed this smile 

 with so much effect as the lively Augustus, who 

 delighted visitors by his inexhaustible humour in 

 1879. The gorilla, of which an illustration is given 



* Darwin, Expression of the Emotions, 



