1892.] Adductor Fibres of the Recurrent Laryngeal Nerve. 105 



the thyro-arytenoideus externus. He passed a ligature round each 

 branch, divided all three branches, and then stimulated each separately 

 by an electrical current, and noted the movements of the vocal cords. 

 The communication is an exceedingly brief one ; but the observer 

 promised to publish a full account of his experiments later. As far 

 as I am aware, no such publication has appeared up to the present. 



These observations can scarcely be said to have thrown much fresh 

 light on the question at issue, as it is only natural to suppose that 

 this nerve, in common with all other motor nerves, should so near its 

 peripheral termination divide into several branches, and that stimula- 

 tion of each branch of the nerve should evoke contraction of the 

 muscle which it supplies, and thus bring about the particular move- 

 ment of the vocal cord over which the muscle presides. But this 

 does not at all decide the all-important question as to whether the 

 nerve fibres presiding over the different functions have a separate 

 course throughout the entire length of the nerve trunk or not. 



Dionisio* performed tracheotomy, and then inserted a laryngeal 

 " dynamometer " between the cords. This consisted of a small india- 

 rubber ball, which communicated by means of a tube with a mer- 

 curial manometer. The height of the mercurial column during 

 inspiration and expiration was then noted during the natural move- 

 ments of the vocal cords, its position during expiration being of 

 course higher than during inspiration. The recurrent laryngeal 

 nerve was exposed and stimulated with an electrical current suffi- 

 ciently strong to produce moderate adduction of the corresponding 

 vocal cord, during which the mercurial column rose. When excitation 

 was discontinued it fell again, and oscillated between the two former 

 points. Circular pressure was then applied to the nerve, commencing 

 with 5 grammes, and going up to 350 grammes, by gradual stages ; 

 pressure being kept up for 2f minutes at each stage. It was found 

 that on stimulating the nerve after each stage there was a gradual 

 diminution in its power of conduction, until stimulation on the 

 proximal side of the point of pressure no longer gave any response, 

 while stimulation on the distal side resulted in a rise of the pressure, 

 but not nearly so great as formerly. There was a gradual fall of pres- 

 sure, the inspiratory and expiratory preserving about the same ratio 

 they bore to each other before the pressure was commenced. 



Operative Procedure. 



Dogs were without exception the animals used in these experiments, 

 and in every case ether narcosis was produced and continued through- 

 out the whole course of the experiment, at the end of which the 

 animal was always killed by an overdose of the narcotic, except in 



* Dionisio, ' Arch. Italiani di Laringol.,' January, 1892, p. 1. 



