Vocal Cords in Quiet Respiration in Man, fyc. 



419 



no means an indispensable adjunct to the purposes of the respiratory 

 process.* 



On the other hand, in order to impart vibrations to the column of air 

 contained in the upper respiratory passages for the purpose of pro- 

 ducing sound, nature chose as the most suitable form a reduplication 

 of folds of mucous membrane within the larynx endowed with 

 certain special characteristics. 



But this reduplication in turn seriously interferes with the calibre 

 of the tube ; that is to say, with the respiratory function of the 

 larynx. 



That this interference is serious can easily be shown anatomically, 

 and, though not quite so obviously, with the material at present in our 

 possession, both physiological and pathological. 



For the first purpose I have made the following measurements! of 

 dead larynges : 



From this table it appears that the transverse diameter of the 

 vestibule of the larynx, on the one hand, and the longitudinal and 

 the transverse diameters of the cricoid cartilage, on the other, are so 

 nearly equal to each other, that in both sexes, without committing 



* At the same time it is perfectly possible that in some species of animals the 

 complete closure of the glottis is by far the most important means of protecting the 

 lower air passages against the entry of food. "With regard to this very complicated 

 question, see the excellent prize essay of Otto Frey, ' Die pathologischen Lungen- 

 veranderungen nach Lahmung der Nervi Vagi,' 1877, p. 81. 



} My numbers referring to the total length of the glottis in men differ somewhat 

 from those of previous observers in that they are a little smaller ; the accuracy of 

 the observations, however, can be vouched for. 



