He was not able to take up small objects with facility, on account of the disproportion of the size of the thumb to the fingers. The metacarpal bone of the thumb has the mobility of a first joint. The form of both the feet and hands gives a great prehensile power, fitted for the woods or forests, the natural _habitat_ of these animals, where it must be almost an impossibility to capture an adult of the species alive. Under the throat is a large black pouch, a continuation of the common integument, very thinly covered with hair, and not very visible when undistended. It has a corrugated appearance, extending from the under part of the chin to the throat, is attached as low down as the upper part of the sternum, and it is also attached above to the symphysis of the lower jaw. The use of this pouch has been a subject of much speculation: having the animal for some time with me, sleeping in the same apartment, I might be able to form some opinion on the subject. Its use is certainly not well known, though it is not improbable that it may be an appendage to the organ of voice. For often when irritated, I have observed him inflate the pouch, uttering at the same time a hollow barking noise,[53] 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 yawning, it was also inflated; and in all instances, (except when excited by anger,) he would gradually 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 contained 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 extent 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 would be beneficial to the beast’s coat, I placed him in a large tub of water: he was much frightened at his situation, and soon began to display a marked hydrophobic symptom, but not the least attempt was made to inflate the pouch, although he was frequently submersed. This animal is destitute of cheek pouches as a reservoir for food.