The man-like apes are from three to six feet tall, and are all of them very strong, the gorilla, who sometimes weighs over three hundred pounds, being about the bravest and most formidable unarmed animal on the planet. They are erect or semi-erect, have loud voices, plantigrade feet, and irritable dispositions—in all of these particulars being strikingly like men. The gorilla, chimpanzee, and gibbon are highlanders, preferring the uplands and mountains. The orang is a lowlander, living phlegmatically among the sylvan swamps of Sumatra and Borneo. The gorilla and chimpanzee are terrestrial, seldom going among the trees except to get food or to sleep. The orang and gibbon are arboreal, seldom coming to the ground except to drink or bathe. They all walk on their hind-limbs, generally in a stooping posture, with their knuckles or fingers touching the ground. But they sometimes walk with their arms hanging down by their sides, and sometimes with their hands clasped back of their heads to give them balance. None of them ever place their palms on the ground when they walk—that is, none of them walk on four feet. The anthropoid races, in the shape of their heads and faces and in the general form and structure of their bodies, and even in their habits of life, resemble in a remarkable manner the lowest races of human beings. This resemblance is recognised by the negro races, who call the gorilla and chimpanzee ‘hairy men,’ and believe them to be descendants of outcast members of their own species. There are differences in structure between man and the apes, just as there are differences in structure between the Caucasian and the Caffre, or even between individual Caucasians or individual Caffres. There are differences in structure and topography, often very noticeable differences, even among members of the same family. But in all of its essential characters, and extending often to astonishing particulars, the structure of man is identical with that of the anthropoid.[2] In external appearances the man-like races differ from men in having a luxuriant covering of natural hair. But anthropoids differ very much among themselves in this particular. The orang, usually covered with long hair, is sometimes almost hairless. There are, too, races of human beings whose bodies are covered with a considerable growth of hair. The Todas (Australians) and Ainus (aborigines of Japan) are noted for the hairiness of their bodies, certain individuals among them being covered with a real fur, especially on the lower limbs.[3]