The Extent of my Experiments—Apes and Baboons—Miscellaneous Records of Sound—The Vocal Index.

In quest of the great secret of speech, I have pursued my investigations chiefly in the direction of learning one tongue, but incidentally I have made many detours, and I have recorded the sounds of many other forms of the animal kingdom, besides primates. I have examined the phonation of lions, tigers, leopards, cats, dogs, birds of many kinds, and the human voice in speech, music, and laughter. Besides these, I have examined various musical sounds, especially of the pipe and whistle kinds.

More than a year ago I made some splendid records of the sounds of the two chimpanzees in the Cincinnati collection. I have not had the opportunity to study these apes themselves, as I desired to do, since they are kept so closely confined in a glass house, and for ever under the eye of their keeper, which conditions are not favourable to the best results. I am not prepared therefore to give much detail concerning their speech; but from a careful study of one cylinder containing a record of their sounds, I was able to discern as many as seven different phones, all of which come within the scope of the human vocal organs. I learned one of these sounds, and on a subsequent visit to Cincinnati I succeeded in attracting the attention of the female, and eliciting from her a response. She would come to the lattice door of the inner cage by which I was standing, and when I would utter the sound she would press her face against the door of the cage and answer it with a like sound. The male, however, did not appear to notice it with any degree of concern. I have no idea what the sound meant, and my opportunities have not been such that I could translate it with the remotest degree of certainty. STUDIES IN TROPICAL AFRICAThese apes will be one of the chief objects of my studies in tropical Africa, as I believe them to possess a higher type of speech even than the gorilla. In this opinion, which I reached from the study of other sounds and the types of skull to which they belonged, I am not alone: Mr. Paul Du Chaillu, Mr. E. J. Glave, and others who have seen both of these apes in their native habitat, agree with me on this point. I am aware that this view is not in strict accord with that of Professor Huxley, who assigns the gorilla the highest place next to man in the order of Nature, and the chimpanzee next below him. I shall not here attempt to discuss the question with so high an authority, and I must confess that the vocal index is not yet so well defined that it may be relied upon in classifying apes. One aim I have in view is to study the gorilla and chimpanzee side by side in their native wilds, and to record, if possible, the sounds of their voices in a wild state. From the study of the sounds I have made, I feel confident that all the vocal sounds made by these apes may be uttered by the human vocal organs.

Some months ago I made a record of the voice of the great Anubis baboon, in Philadelphia. I did not expect to find in him an elevated type of speech; but my purpose was to compare it with other Simian sounds, to see if I could not establish a series of steps in the quality of vocal sounds which would coincide with certain other characters. I had found by the study of certain cranial forms that certain vocal types conformed to certain skulls, and were as much a conformation thereof as are the cerebral hemispheres. I then believed, and have had no cause since to recede from it, that the vocal powers were correctly measured by the gnathic index; that the mind and voice were commensurate; and that as the cranio-facial angle widens the voice degrades in quality and scope. In man, I find the highest vocal type, and just as we descend in the cranial scale, the vocal type descends into sounds less flexible, less capable, and less musical. These deductions apply only to mammals; among birds, insects, &c., a different order may prevail.

The records of the lions show some strange features in the construction of sound; and when analysed on the phonograph present some novel effects. The sound as a whole appears to be broken into broad waves or pulsations; but on analysing it the fundamental tones somewhat resemble the sounds produced by drawing a mallet rapidly across the keyboard of a xylophone, and are characterised by a peculiar resonance something like the tremulous vibrations of a thin glass containing a small quantity of water. Each of these separate fundamental sounds, or sound units as they appear to be, can be further reduced to still smaller vibrations; and the result suggests that the fundamental sounds themselves are an aggregation of smaller vibrations. I have not as yet been able to compare the notes one by one with the scale of the xylophone in order to ascertain whether or not they obey the laws of sound upon which is founded the chromatic scale of music. The lion makes only a small number of different sounds, nearly of the same pitch. I have not analysed the vocal sounds of the other felines to ascertain to what extent they coincide with those of the lion; but his appear to be somewhat unlike any other sounds which I have examined.

Among the few sounds of birds which I have analysed, I may mention the Trumpeter Crane. I have made one record of this bird which was sufficiently loud to enable me to obtain some idea of the character of the sound. I am in doubt as to what the real mode of producing this sound is. The volume of sound evidently comes from the mouth of the bird; but while in the act of making it, he appears to bring the whole body into use, even the feathers appear to take some part in its production, and the whole frame of the bird vibrates in the act. The record which I have shows some resemblance, on analysis, to the sound made by the lion; but it is not sufficiently strong to admit of analysing the sound units or fundamental sounds.

From the many sounds that I have analysed, it appears to me that there is a difference in the phones of all different genera, and that the phonetic basis of human speech more closely resembles that of the Simian than any other sounds; but I wish to be understood distinctly not to offer this in evidence to establish any physical, mental, or phonetic affinity between mankind and Simians. I merely state the facts from which all theorists may deduce their own conclusions.