Vocal Cords in Quiet Respiration in Man, $r. 



nitcly settle the question, because in animals, especially under the 

 influence of anaesthetics, only rarely is a condition observed during 

 respiration analogous to that seen in quiet respimtion in man, their 

 vocal cords, on the contrary, making very energetic rhythmical ex- 

 cursions. Still, it seemed legitimate to submit this question to 

 experimental proof, because, even with these respiratory excursions, 

 it was to be expected that if respiratory influences governing the 

 action of the glottis-openers reached the respiratory centres along 

 the trunks of the pneumogastric nerves, the excursions of the vocal 

 cords after section of the latter would very much diminish in in- 

 tensity, and, if they were exclusively conducted along these paths, that 

 after section of the pneumogastn'cs below the points of departure of 

 the recurrents, the glottis would not open any further than to the 

 cadaveric position. 



Professor Victor Horsley was kind enough to submit these 

 theoretical considerations to experimental proof. On April 17, 1890, 

 he, in the presence of Mr. Embleton and of myself, performed the 

 following experiment : A small adult female fox terrier was etherised 

 and tracheotomised ; the narcosis was afterwards kept up with 

 chloroform. First the right, afterwards the left, vagus was laid bare, 

 and both nerves were cut about 1 centimetre below the points where 

 the right recurrent laryngeal winds round the subclavian artery and 

 the left round the aorta. As soon as the pleura was opened in order 

 to get at the left vagus, artificial respiration was started and main- 

 tained until the end of the experiment. 



Whilst previous to the cutting of the right vagus (and also after 

 the division) the thorax as well as the vocal cords made very extensive 

 and energetic rhythmical respiratory excursions (the glottis during 

 inspiration being opened to its fullest extent), the respiratory excur- 

 sions of the cords were, after section of the second vagus (the left), 

 equally energetic, but much less extensive, the glottis during respira- 

 tion opening only to the cadaveric position. 



The animal was killed by asphyxia; during its final forcible respi- 

 ratory efforts the glottis again opened, during inspiration, to its fullest 

 extent. 



Dissection after death showed that both recurrent nerves were 

 quite uninjured. 



This experiment certainly went far to prove that respiratory 

 impulses influencing the action of the posterior crico-arytenoid muscles 

 reached the respiratory centre, and, more precisely speaking, the gan- 

 glionic centres of these abductor muscles, through the medium of the 

 pneumogastric nerves. At the same time the full dilatation of the 

 glottis during the asphytic stage of the animal, seemed to point out 

 that the impulses thus engendered cannot be the only ones reaching 

 these ganglionic centres, and that the respiratory centre, so far as the 



