UNGKA APE. 151 



him inflate the pouch, uttering at the same time 

 a hollow barking noise,* for the production of 

 which the rushing of the air into the sac was 

 evidently an adjunct. The inflation of the pouch 

 was not, however, confined to anger ; for when 

 pleased he would purse the mouth, drive the air 

 with an audible noise into the sac ; when yawn- 

 ing, it was also inflated ; and in all instances, 

 (except when excited by anger,) he would gra- 

 dually empty the sac, as if he derived a pleasure 

 from it. When the sac has been distended, I 

 have often pressed on it, and forced the air con- ' 

 tained within it into the mouth, the animal not 

 evincing at the time any sign of its being an 

 annoyance to him. When uttering the barking 

 noise, the pouch is not inflated to the same ex- 

 tent as when he yawns. It has been stated in 

 an American publication, that the use of the air 

 sac is for a swimming bladder. It may be said 

 in refutation, (if the assertion is not too absurd to 

 refute,) that Ungka never evinced any partiality 

 for swimming, although provided with such an 

 apparatus ; but one day, thinking that a washing 



* When the barking noise was made, the Hps were pursed 

 out, and the air driven into the sac, at the same time that 

 tlie sound was uttered, the lower jaw was also a little 

 protruded. 



