Vocal Cords in Quiet Respiration in Man, fyc. 417 



variations of nerve supply, not only in different kinds of animals, but 

 even in animals belonging to the same species ; and again, as will 

 hereafter be shown, the immediate effects of the division of the 

 motor nerves of the larynx, as well as its ultimate consequences, are 

 different according to the age of the animals used for the experi- 

 ments. 



Thus, unless care is taken, all these circumstances combine to 

 reduce, in this particular question, the value of experiments on 

 animals for the solution of the corresponding question in men. Still, 

 even if regard be had to all these circumstances and possible sources 

 of error, the fact remains that by all observers narrowing of the 

 glottis in all kinds of animals has been reported after division of the 

 motor nerves of the larynx, and that by some of these observers the 

 state of things thus resulting is expressly contrasted with the position 

 as previously present during quiet respiration. 



A general survey of the mass of evidence so far accumulated proves 

 beyond doubt that the glottis is wider open during quiet respiration 

 (inspiration and expiration) than it is after death or after division of 

 the pneumogastric and recurrent laryngeal nerves. The statements of 

 the most trustworthy and experienced observers on men, the reports 

 of all physiologists who have investigated this question by experi- 

 ments on animals, and especially the direct comparative measure- 

 ments of the glottides of quiet-breathing healthy adults and of dead 

 adult bodies all go to establish one and the same result, and leave, I 

 think, no doubt as to the actuality of the fact that the glottis in man 

 during quiet respiration is wider open than after death. 



The immediate outcome of this result is, as already stated in a 

 previous paragraph, that the position of the vocal cords during quiet 

 respiration can neither represent an equilibrium between the anta- 

 gonistic adductor and abductor muscles of the lai*ynx, nor the result 

 of inaction of both of them. In either of these two hypothetical 

 conditions the width of the glottis during qniet respiration could not 

 but be identical with that seen after death. 



As matters actually stand, the state of the glottis during quiet 

 respiration must necessarily be the result of active muscular contrac- 

 tion, and must represent one of two conditions, viz., ^either simul- 

 taneous activity of both the adductors and the abductors of the vocal 

 cords with preponderance of the latter, or, secondly, some degree of 

 activity on the part of the latter alone the adductors being not at 

 all in a state of functional activity. An attempt will be made here- 

 after to show that the second of these alternatives in all probability 

 corresponds with the actual facts. But before proceeding to a discus- 

 sion of this point, the question which naturally arises from the fact 

 that the glottis is wider during qniet respiration than after death 

 demands a reply : What is the cause of this difference ? 



