It will therefore be convenient in endeavoring to form a notion of what we are justified in believing about these animals, to commence with the best known man-like Apes, the Gibbons, and Orangs; and to make use of the perfectly reliable information respecting them as a sort of criterion of the probable truth or falsehood of assertions respecting the others.

Of the Gibbons, half a dozen species are found scattered over the Asiatic Islands, Java, Sumatra, Borneo, and through Malacca, Siam, Arracan, and an uncertain extent of Hindostan on the mainland of Asia.  The largest attain a few inches above three feet in height, from the crown to the heel, so that they are shorter than the other man-like Apes, while the slenderness of their bodies renders their mass far smaller in proportion even to this diminished height.

Dr. Salomon Mueller, an accomplished Dutch naturalist, who lived for many years in the Eastern Archipelago, and to the result of whose personal experience I shall frequently have occasion to refer, states that the Gibbons are true mountaineers, loving the slopes and edges of the hills, though they rarely ascend beyond the limit of the fig-trees.  All day long they haunt the tops of the tall trees, and though toward evening, they descend in small troops to the open ground, no sooner do they spy a man than they dart up the hillsides and disappear in the darker valleys.

All observers testify to the prodigious volume of voice possessed by these animals.  According to the writer whom I have just cited, in one of them, the Siamang, “the voice is grave and penetrating, resembling the sounds goek, goek, goek, goek, goek ha ha ha ha haaaaa, and may be easily heard at a distance of half a league.”  While the cry is being uttered, the great membranous bag under the throat which communicates with the organ of voice, the so-called “laryngeal sac,” becomes greatly distended, diminishing again when the creature relapses into silence.

M. Duvaucel, likewise, affirms that the cry of the Siamang may be heard for miles—­making the woods ring again.  So Mr. Martin describes the cry of the agile Gibbon as “overpowering and deafening” in a room, and “from its strength, well calculated for resounding through the vast forests.”  Mr. Waterhouse, an accomplished musician as well as zooelogist, says, “The Gibbon’s voice is certainly much more powerful than that of any singer I ever heard.”  And yet it is to be recollected that this animal is not half the height of, and far less bulky in proportion than, a man.

[Illustration:  A GIBBON.]

There is good testimony that various species of Gibbon readily take to the erect posture.  Mr. George Bennett, a very excellent observer, in describing the habits of a male Hylobates syndactylus which remained for some time in his possession, says:  “He invariably walks in the erect posture when on a level surface; and then the arms either hang down, enabling him to assist himself with his knuckles;