CHAPTER XIX. 



LARYNX AND TRACHEA. 



BY E. VERSON. 



A. LARYNX. 



FRAMEWORK. The changes in the form and disposition of 

 parts that the modulation of the voice necessitates in the 

 trachea, as the organ for the production of musical sounds, are 

 effected exclusively by voluntary muscles, which, however, re- 

 quire firm points of attachment to enable them to act effect- 

 ively. Such points are afforded by the cartilaginous framework, 

 the composition and arrangement of the separate parts of which 

 render a multiplicity of movements practicable, which vary in 

 the different classes of animals with the requirements of their 

 vocal capability. 



The rudimentary trachea of the Proteus presents only a band 

 of cartilage on each side ; but from this, as Henle has demon- 

 strated, there is developed, if we follow its variations through 

 the ascending series of animals, by subdivision and outgrowth, 

 and again by partial resorption, that complexity of structure 

 which culminates in the form and powers of execution possessed 

 by this organ in Man. 



The division of the simple cartilaginous plate at the side of 

 the trachea, found in the lower classes of animals, into the 

 seven or more pieces present in the higher Mammals, necessi- 

 ates also the development of a ligamentous apparatus to give 

 support to the several parts ; and hence the description of the 

 framework of the trachea demands the consideration, not only 



