202 Mr. Bishop's Experimental Researches into 



tensity, including the key or pitch and the whole range of mo- 

 dulation ; 



And, secondly, the interrupted sounds, or voces limitatae, 

 which constitute articulate language. 



To the former division of these functions the following ob- 

 servations are applied. 



The difficulties which for more than twenty centuries have 

 obstructed the elucidation of this interesting branch of natural 

 philosophy, may be ascribed to two principal causes. 



First, The organs of voice, when anatomically examined, are 

 found to be extremely complex, including portions of a system 

 which is adjusted to perform several of the most important 

 functions of the animal ceconomy. 



Secondly, The stateof acoustic science is notyet sufficiently ad- 

 vanced to estimate all the effects resulting from air in conjunction 

 with an elaborate series of elastic bodies in producing sounds. 



The former of these difficulties has been in a great measure 

 removed by Albinus, Bichat, Majendie, and others, and the 

 latter have been considerably reduced by the investigations of 

 M. FeHx Savart. 



Many of the phaenomena of the voice, however, yet remain 

 unexplained, and abound with subtile intricacies. Several of 

 these which are of fundamental importance, the details of which 

 this memoir consists, will, I trust, tend to illustrate. 



The organs which are associated in the performance of the 

 functions of the voice ai'e principally the lungs, the trachea, the 

 larynx, pharynx, nostrils, and the mouth with its appendages. 



In reference to the vocal organs, the lungs may be I'egarded 

 as a receptacle of air for their supply. 



The Trachea is nearly a cylindrical pipe forming the Porte- 

 vent and the connecting link between the lungs and the larynx. 

 Its anatomical structure is well known, but its office, with re- 

 spect to the voice, has hitherto been very imperfectly under- 

 stood. It varies in length and diameter with the sex and age 

 of the individual. In the adult male it is about four inches 

 and a half in length, and from six to eight tenths of an inch 

 in diameter : in the female, the length is about four inches, 

 and the diameter from nine to eleven twentieths of an inch. 

 It is open at both ends, for the free transmission of air ; its 

 lower extremity having a double embouchure called bronchia, 

 which diverge at an angle of about fifteen degrees from the axis 

 of the trachea. 



The areas of the bronchial tubes are collectively greater than 

 that of the trachea, owing to which the condensation of the air 

 in the latter is more rapidly effected, and the voice acquires, 

 according to M. Savart, a roundness and fulness which it 

 would not otherwise have possessed. 



