the Physiology of (he Human Voice 203 



The important properties of the trachea with respect to the 

 voice are its elasticity, its power of suffering elongation and con- 

 traction, as well as of increasing or diminishing its diameter, and 

 the adaptation of its surface to vibrate in unison with the glottis. 



The Larynx is situated on the top of the trachea, and forms 

 the superior termination of the vocal tube. Its mechanism 

 and functions are exceedingly complicated, and furnish fit 

 subjects both for anatomical and for philosophical discussion. 

 It is the most important organ of the voice, and its struc- 

 ture requires to be well understood before its functions can be 

 satisfactorily explained. Some brief anatomical details will 

 therefore here be introduced. The larynx is a cartilaginous 

 tube situated in the anterior part of the neck, and separated 

 from the cervical vertebras by the pharynx, within which it has 

 a motion resembling that of the slides of a telescope. Its fi- 

 gure, although difficult to describe with precision, is symme- 

 trical: broad and capacious in its superior chamber, it becomes 

 narrower at its lower termination, where it is joined to the 

 trachea, and presents externally an appearance very dissimilar 

 to its internal conformation. 



The frame of the larynx is composed of elastic cartilages, 

 articulated with each other by fibrous and muscular bands in 

 such a manner as to allow a free passage for the transmission 

 of the air in respiration, as well as that mobility which is ne- 

 cessary to the production of the voice. They are five in num- 

 ber : the Thyroid, the Cricoid, the two Arytenoid cartilages, 

 and the Epiglottis. 



TheThyroid*, the largest of these cartilages, lies in the front 

 of the larynx, where it seems both to shield the internal me- 

 chanism from injury, and to contribute to its peculiar function. 

 It is composed of two lateral portions united at the mesial line, 

 where they form an angle more or less acute. These lateral 

 surfaces are nearly smooth, and terminate in four borders ; the 

 superior connected by ligaments with the os hyoides, and the 

 inferior with the cricoid cartilage ; whilst the two posterior bor- 

 tlers give attachment to some fibres of the Stylo- and Palato- 

 Pharyngei muscles, and send off four angular processes, two of 

 M'hich are connected by ligaments with the extremities of the 

 OS hyoides above, and two with the cricoid cartilage below. 



The Cricoid Cartilage*^ situated at the bottom of the la- 

 rynx, serves by its annular shape and dense structure to form 

 the solid portion of the vocal tube. It is narrow anteriorly, 

 where it is connected with the thyroid, from which point it 

 becomes gradually larger, and presents posteriorly a broad 

 portion, on the most elevated part of which are seen two oblique 



* Plate HI., Fig. 1. 

 Z2 



