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* 



may be seen in the bagpipe, where the porte-vent is attached to the 

 chanter or voicing part by a flexible joint or by leather, and the tone 

 is in consequence squeaking and uncertain. 



" Besides thus giving rigidity, firmness and tension to the organ 

 of voice, the thyroid body also acts in another capacity as a loader. 

 In most musical instruments, loaders are used to render the vibra- 

 tions slower and longer, and the tone in consequence fuller, louder 

 and deeper. They compensate for want of size and space, and give to 

 a small instrument, or to a small vibrating or voicing part of an instru- 

 ment, the power and quality of a large one. The human organ of 

 voice is 8 inches long, and has the same power and better quality of 

 tone than the instrument that most nearly approaches it, the 

 French horn, which is 9 feet, or the " vox humana" pipe of a mode- 

 rate-sized organ, which is from 4 to 8 feet long. This economy of 

 size in the human organ has always been wondered at, but never, 

 that I know, explained. Besides the thyroid body, another part, 

 the structure of which I shall describe on another occasion, aids in 

 this admirable economy. The nearer mechanism of human design 

 approaches to perfection, the more it resembles similar structures in 

 animal mechanics. The base of all stringed instruments and musical 

 boxes is loaded : in most wind instruments the voicing part is thus 

 loaded and strengthened, as in the organ pipe, horn, flute, clarionet, 

 &c. The bassoon, which in its lower notes approaches the human 

 voice, is uncertain and wheezy in tone for want of this provision. 



" When the thyroid body is small and thin, the voice will be found 

 to be small and shrill ; when large, the tone will be full and sonorous ; 

 when it is morbidly enlarged, the voice will be deeper and more 

 base ; and when very large, as in bronchocele, the voice will be 

 smothered. 



"The compass of the voice is in great part produced by the 

 raising and lowering of the larynx, the shortening and lengthening 

 of the vocal tube. The thyroid body partakes of this motion, at 

 the same time firmly fixing and rendering tense the parts in each 

 position. By its change of shape, bulk and density flattening and 

 thinning when the larynx is raised, enlarging and bulging when it 

 is lowered it aids in giving the particular tone or pitch, high and 

 acute in the first case, full and deep in the second ; and, in like man- 

 ner, by its varying shape, bulk, density, and pressure, it takes a great 



