4?>2 Dr. F. Semon, On the Position of the 



larynx is concerned, may also be influenced through other afferent 

 impulses. 



To settle this point, if possible, more definitely, the experiment was 

 repeated on May 8, 1890. A small castrated fox terrier was etherised 

 and tracheotomised. Narcosis was afterwards kept up by ether. 



The right vagus was laid bare below the line of departure of the 

 right recurrent laryngeal nerve. Both cords made very energetic 

 and extensive rhythmical respiratory excursions. The right vagus 

 was cut more than 1 cm. below the point of departure of the right 

 recurrent laryngeal nerve. Both cords continued their excursions as 

 if nothing had happened. 



A subcutaneous injection of 5 grains of acetate of morphia was now 

 made into the dog's thigh, the left vagus was then exposed, artificial 

 respiration being started as soon as the pleura was opened previous 

 to the section of the left vagus. It was again ascertained that the 

 glottis still opened at maximum during inspiration. The left vagus 

 was then cut about 1 cm. below the arch of the aorta, and it was now 

 observed that, together with very considerable slowing of the two 

 phases of respiration, the glottis, though it still opened widely, and 

 certainly much beyond the cadaveric position, yet no longer opened 

 nearly as widely as before, when the vocal cords during inspiration 

 actually completely disappeared from view. 



A very remarkable phenomenon was observed in connexion with 

 the artificial respiration. Whenever the dog's lungs were well aerated, 

 the excursions of the cords, though good, corresponded to the descrip- 

 tion given above of the conditions as occurring after section of the 

 vagi, but as soon as asphyxia became threatening the glottis at once 

 opened, as previously to the section, ad maximum. 



The dog was killed by asphyxia. Post-mortem examination showed 

 that both vagi had been cut very considerably below the points 

 where the recurrents were given off, and that the latter were quite 

 uninjured. 



This experiment, then, in every respect tends to corroborate the 

 conclusions drawn from the former, i.e., that whilst the inspiratory 

 impulses which act upon the ganglionic centres of the abductor 

 muscles and which in animals more frequently induce rhythmical 

 excursions of the vocal cords, but in man tonic semi-dilatation of the 

 glottis, are of a reflex character, and are mainly conducted along the 

 pneumogastric nerves, yet the latter are by no means the only source 

 of this reflex innervation. 



The question . raised in the foregoing paragraphs will certainly 

 demand still further elucidation, and the results arrived at in this 

 paper will no doubt have to be checked by future observers. Still I 

 think that, as the outcome of the investigation, so far as it has been 

 conducted, the following conclusions may be drawn : 



