But all this was only childish prattle in comparison with the daily performances of the big white-handed, and the black hoolock gibbons, now and for several years past residing in our Primate House. Every morning, and perhaps a dozen times during the day, those three gibbons go on a vocal rampage and utter prolonged and ear-splitting cries and shrieks that make the welkin ring. The shrieking chorus is usually prolonged until it becomes tiresome to the monkeys. In all our ape and monkey experience we never have known its equal save in the vocal performances of Boma, our big adult male chimpanzee, the husband of Suzette. A baboon emits occasionally, and without any warning, a fearful explosive bark, or roar, that to visitors is as startling as the report of a gun. The commonest expressions are "Wah!" and "_Wah'_-hoo!", and the visitor who can hear it close at hand without jumping has good nerves. The big and solemn long-nosed monkey of Borneo (_Nasalis larvatus_) utters in his native tree-top (overhanging water), a cry like the resonant "honk" of a saxophone. He says plainly, "Kee honk," and all that I could make of its meaning was that it is used as the equivalent of "All's well." Of all the monkeys that I have ever known, either wild or in captivity, the red howlers of the Orinoco, in Venezuela, have the most remarkable voices, and make the most remarkable use of them. The hyoid cartilage is expanded,--for Nature's own particular reasons,--into a wonderful sound-box, as big as an English walnut, which gives to the adult voice a depth of pitch and a booming resonance that is impossible to describe. The note produced is a prolonged bass roar, in alternately rising and falling cadence, and in reality comprising about three notes. It is the habit of troops of red howlers to indulge in nocturnal concerts, wherein four, five or six old males will pipe up and begin to howl in unison. The great volume of uncanny sound thus produced goes rolling through the still forest, far and wide; and to the white explorer who lies in his grass hammock in pitchy darkness, fighting off the mosquitoes and loneliness, and wondering from whence tomorrow's meals will come, the moral effect is gruesome and depressing. In captivity the youthful howler habitually growls and grumbles in a way that is highly amusing, and the absurd pitch of the deep bass voice issuing from so small an animal is cause for wonder. It is natural that we should look closely to the apes and monkeys for language, both by voice and sign. In 1891 there was a flood of talk on "the speech of monkeys," and it was not until about 1904 that the torrent stopped. At first the knowledge that monkeys can and do communicate to a limited extent by vocal sounds was hailed as a "discovery"; but unfortunately for science, nothing has been proved beyond the long-known fact that primates of a given species understand the meaning of the few sounds and cries to which their kind give utterance.