474 MUSCULAR MOTION. 



fied in intensity and quality by actions of the larynx and vocal tube, so 

 as to give rise to the deceptions we experience. It is known, that our 

 appreciation of the distance and nature of a sonorous body is formed 

 from the intensity and quality of the sound proceeding from it. We 

 instinctively believe, that a loud sound proceeds from a near object, 

 and a feeble sound from one more remote ; accordingly, if the intensity 

 and quality of the sound from a known body be such as to impress us 

 with the idea that it is more remote than it really is, we incur an acous- 

 tic illusion. The ventriloquist takes advantage of this source of illu- 

 sion ; and, by skilfully regulating the force and timbre of his voice, 

 leads us irresistibly into error. Mr. Dugald Stewart 1 gives some exam- 

 ples of this kind of illusion. He mentions having seen a person, who, 

 by counterfeiting the actions of a performer on the violin, whilst he imi- 

 tated the music by his voice, riveted the eyes of the audience on the 

 instrument, although every sound they heard proceeded from his own 

 mouth. Mr. Savile Carey, who imitated the whistling of the wind 

 through a narrow chink, told Mr. Stewart, that he had frequently 

 practised the deception in the corner of a coffee-house, and that he sel- 

 dom failed to see some of the company rise to examine the tightness of 

 the windows ; whilst others, more intent on the newspapers, contented 

 themselves with putting on their hats, and buttoning their coats. 2 It 

 is to account for the mode in which this is effected, that different hypo- 

 theses have been from time to time entertained. Haller, Nollet, Mayer, 3 

 and others, believed, that the voice is formed during inspiration ; but 

 this does not seem to be the case. Voice can certainly be effected 

 during inspiration ; but it is raucous, unequal, and of trifling extent 

 only. MM. Dumas and Lauth 4 considered ventriloquism to be a kind of 

 rumination of sounds ; the voice, formed in the larynx, being sent into 

 the interior of the chest, attaining there a peculiar timbre, and issuing of 

 a dull character. M. Richerand is of opinion, that the whole mechanism 

 consists in a slow, gradual expiration, which is always preceded by a 

 deep inspiration. By means of this, the ventriloquist introduces into 

 his lungs a considerable quantity of air, the exit of which he carefully 

 regulates ; and a similar view is embraced by Prof. J. Miiller, 5 who 

 asserts that the sounds uttered by the ventriloquist can be perfectly 

 elicited by a method, which, he is convinced, must be adopted by ven- 

 triloquists. This method consists in inspiring deeply so as to protrude 

 the abdominal viscera by the descent of the diaphragm, and then speak- 

 ing, whilst expiration is performed very slowly through a narrow glottis 

 by means of the lateral parietes of the thorax alone, the diaphragm 

 maintaining its depressed position ; and M. Colombat confirms the 

 general accuracy of Professor Miiller's view, remarking that by con- 

 tinually practising in a manner somewhat similar to that pointed out by 

 him he was enabled to attain considerable skill in the production of 



1 Elements of the Philosophy of the Human Mind, 3d edit., Lond., 1808; Amer. edit., 

 Brattleborough (Vermont), 1813. 



3 Brewster, Natural Magic, Amer. edit., p. 158, New York, 1832. 



* Lepelletier, Physiologic Medicale, &c., iv. 213, Paris, 1833. 



4 Memoir, de la Societe des Sciences Agricol. de Strasbourg, i. 427. 



* Elements of Physiology, by Baly,p. 1054, Lond., 1838. 





