Page:Popular Science Monthly Volume 9.djvu/420

396 another according to the obstacles opposed by the tongue, the teeth, and the lips.

It has been demonstrated that the sounds of speech are formed in the buccal cavity, by processes which vary within very narrow limits. Authors who have studied in their own persons the pronunciation of the vowels and consonants describe with great minuteness the positions assumed by the lips, the tongue, the soft palate, under all circumstances, and give drawings which show the various operations we perform while articulating letters and syllables. These observations possess great interest; but yet the rules thence derived are not so rigorously true as to be indisputable. As Mandl observes, sounds that are nearly identical are produced with different positions of the organs of speech. If a person has lost all his teeth, he modifies the play of the lips and tongue, and so contrives to speak intelligibly. The voices of persons we know can be imitated so that the deception shall be perfect. By changing the timbre, the voice is made to sound as though it came from a cavern; this is the ventriloquist's art. Persons who had had the misfortune to lose a considerable portion of their tongue, have been able to converse, though it is not affirmed that hearing them speak would be a pleasure. Some birds find it possible to utter sounds which with us require the use of the lips. In a word, there is nothing absolute in the acts which produce speech, though in general the same organs do not differ very much in their mode of procuring the same results, as may be shown from the fact that congenital deaf-mutes who have learned to speak interpret the movements of the mouth with infallible certainty; they see the speech of the interlocutor. This proves that our modes of articulation present only shades of difference.

The phenomenon of deaf-mutes capable of speech has long been esteemed a marvel. In the middle ages there was one instance of this, the credit of which is due to the patience and skill of Beverley, Archbishop of York. In the sixteenth century, the universal scholar, Jerome Cardan, discussed the possibility of teaching the use of the voice to congenital mutes. About the same period, the Spanish monk Pedro de Ponce was, according to an epitaph, famous throughout the whole world for his power of causing mutes to speak. He had for his pupils two brothers and one sister of Pedro de Velasco, and the son of Gaspar de Guerra, Governor of Aragon. Some time later, Juan Pablo Bonet, in a work which is the oldest known upon this subject, treated of the art of giving speech to the dumb. In