VOICE IN ANIMALS. 215 



pendent only on breath, and resulting from the vibration produced by 

 the friction of the air against the margins of the opening. In laugh- 

 ing, on the contrary, the sounds given forth are true vocal tones con- 

 vulsively repeated. 



Imperfections of speech, such as lisping, stammering, or stuttering, 

 are due to errors in the action of the organs of speech. Stammering 

 is almost always caused by some irregular action of the nervous cen- 

 tres, and is chiefly produced by temporary spasm of the glottis, asso- 

 ciated with embarrassment in other parts concerned in articulation. 

 It may originate in nervousness, or fright, and sometimes in imitation 

 or affectation. By patient and persevering practice, founded on an 

 accurate perception of the erroneous movements, and their correct 

 substitutes, or by the recovery of self-confidence, these imperfections 

 may generally be remedied. Dumbness is not, in any way, necessarily 

 connected with defective development of the organs, concerned in the 

 production of speech ; for deaf-mutes can be taught to speak, and ac- 

 quire a rude kind of language. This last is an affliction conjoint, from 

 birth, with deafness, the ear no longer serving as a guide for the pur- 

 poses of articulation. Some mutes, however, are not deaf; the ab- 

 sence of speech, in such cases, being due, either to a malformation in 

 the organs employed, or else to some defect in that part of the central 

 organ of the nervous system connected with its production. It is 

 said that persons who have become deaf, and remained absolutely so 

 for many years, may forget how to speak, and so become dumb. 



The nature of the peculiar kind of speech called ventriloquism, is 

 obscure. It was supposed by Magendie to be produced in the larynx, 

 by variously modifying the voice, so as to imitate the changes imparted 

 to it by distance. It has also been thought to be simply produced by 

 articulating during the act of inspiration. According to Muller, the 

 sound of the voice peculiar to ventriloquism, may be imitated, after 

 taking a deep inspiration, so as to cause the .protrusion of the abdom- 

 inal viscera by the descent of the diaphragm, and maintaining this 

 muscle in its depressed condition, by speaking during a very slow ex- 

 piration, performed only by the lateral parietes of the chest, through 

 an exceedingly narrow glottis. Many attempts have been made by 

 Faber, Kempelen, and others, to construct speaking automata, but 

 with very partial success, the separate sounds being imitated, but not 

 the mode of combination necessary for the production of Speech. 



Voice in Animals. 



The organ of voice in the different orders of Mammalia, presents various 

 degrees of development, being in some, highly complex in structure, in others 

 more simple in form ; but in all, presenting a general anatomical and physio- 

 logical resemblance to the vocal apparatus of Man. Among the so-called 

 Quadrumana, some are provided with large sacs, situated between the thyroid 

 cartilage and hyoid bone ; these exercise a considerable influence in modifying 

 and increasing the resonance of the voice. The acute tone and hoarse quality 

 of the cry in some of the monkeys of the old continent, are due to the presence 

 of laryngeal sacs. The intensity of the voice, in some species of American 

 monkeys, the howlers, is very great ; this is dependent both on the size of the 

 epiglottis, and on the existence of cavities of considerable magnitude in the 



