418 Dr. F. Semon. On the Position of the 



A reply to this question will be given by a consideration of the 

 physiological functions of the larynx. 



The larynx serves two functions, which are in a certain sense inti- 

 mately connected with, yet in another sense just as distinctly anta- 

 gonistic to, each other. These are the functions of respiration and 

 of phonation. For the purpose of the former which with regard to 

 the vital interests of the individual is by far the more important one 

 of the two it is indispensable that the lumen of the air tubes should 

 be wide enough open to admit of the ingress and egress of the 

 quantity of air necessary for breathing purposes, without at the same 

 time imposing an additional labour upon the other respiratory 

 muscles. Such an additional labour would arise if the portal for the 

 entry and exit of air were so narrow that the air, instead of quietly 

 passing, had, by forcible means, to be sucked through it. 



On the other hand, the function of phonation makes it a necessity 

 that an apparatus should be interpolated within the air tubes which 

 would admit of complete juxtaposition of the voice- producing organs. 



This interpolation, in all probability, was meant for the purposes of 

 phonation only, not primarily for respiratory purposes. 



I am perfectly well aware that in a certain sense the interpolation 

 of the phonatory apparatus, represented by the vocal cords, subserves 

 also the protection of the lower respiratory passages against the 

 entiy of foreign bodies : but that this interpolation is not indis- 

 pensable is conclusively shown by comparative anatomy. The purpose 

 of protection is, indeed, as demonstrated by the latter science, suffi- 

 ciently provided for by the " constrictor vestibuli laryngis" (Luschka) 

 or " thyreo-ary-epiglotticus " muscle (Henle), which forms the upper- 

 most stratum of the sphincter muscles of the larynx. In Reptiles a 

 sphincter of the simplest form surrounding the vestibule of the 

 larynx is the only protective arrangement (Henle, ' Anatomic,' vol. 2, 

 p. 249), and even in dumb Mammalia the same simple arrangement 

 returns. " In the Cetaceous Mammalia," says Mayo (' Outlines of 

 Human Physiology,' 1839, p. 380), "which are dumb, we find a 

 respiratory larynx alone ; the windpipe terminates in a contractile 

 circular aperture, and this opens not at the root of the tongue, but is 

 prolonged as a pipe towards the nostrils completely out of the way 

 of food." In man, again, a contraction of the constrictor vestibuli 

 of the larynx sufficiently guards the lower air passages against the 

 entry of foreign bodies, as shown by the numerous cases in which, 

 though destruction of the phonatory apparatus (vocal cords) had 

 taken place through disease, yet accidents from food, &c., " going the 

 wrong way " occur no more frequently, than in people in whom 

 these parts are intact. 



Thus comparative anatomy as well as pathological observation on 

 men combine to show that the interpolation of the vocal cords is by 



