32 ANATOMY AND PHYSIOLOGY OF 



the right and left superior nerves of the larynx. The first hypothesis was unsup- 

 ported by anything that we knew of the parts. The second seemed unlikely, since 

 on reflection we could recall no instance of a true chiasm of any nerves except those 

 of sio-ht. We hastened to examine the question by new experiments. 



Experiment. — Snapper, weight two pounds. We exposed and galvanized the left 

 inferior laryngeal nerve, thus causing botli lips of the glottis to open. The same 

 result was obtained with the right nerve. This fact, observed by us in other cases, 

 was soon found to be due to the difficulty of insulating the current in one nerve. 

 When, however, we made use of mechanical irritants, stimulation of one nerve 

 affected only the glottic lips of the same side. 



The right inferior laryngeal nerve was then cut, and immediately afterwards the 

 right superior laryngeal nerve. The glottis still moved as well as before these 

 sections. Next, we cut the left recurrent (inferior laryngeal nerve), thus leaving 

 the left superior laryngeal the only nerve entire. Nevertheless, the glottic lips 

 on both sides opened and shut, as well and as completely as ever. Lastly, we cut 

 this remaining nerve, causing total paralysis of the glottis, and the usual results as 

 to respiration. 



Order of section, and results : — 



1st. Cut right recurrent nerve (inferior laryngeal) and rig t superior laryngeal 

 nerve; glottis continues to move perfectly on both sides. 



2d. Cut left recurrent (left inferior laryngeal) ; glottic action perfect on both sides. 



3d. Cut left superior laryngeal nerve ; total paralysis of glottis. 



Experiment. — Snapping turtle, weight three and a half pounds. We dissected 

 the hyoid apparatus from its connection with the lower jaw, and held it back, thus 

 freely exposing to view the chink of the glottis. Up to this time we had reached 

 the conclusion, that somewhere on the fenestrum in the cricoid cartilage there 

 might be a branch of communication between the two superior laryngeal nerves of 

 the larynx. Therefore, on the turtle prepared as above described, we made an 

 incision on to the fenestra] membrane, between the larynx and the hyoid bone, 

 opposite to the junction of the superior cornu with this bone. The section made a 

 little to the left of the median line caused slight twitching in the glottic muscles, 

 but had no influence on the respiratory motions of the glottis. 



The two inferior laryngeal nerves were next divided, and still the glottis moved 

 as perfectly as before. The left superior laryngeal nerve was divided at the middle 

 of the upper hyoid cornu, and immediately all motion of the left side of the glottis 

 ceased, the right side moving during respiration as usual, although somewhat 

 feeblv, owing perhaps to loss of blood during the first part of the experiment. 



Section of the right superior laryngeal nerve completed the paralysis of the glottis. 



Onlrr of section, and remits: — 



1st. Section through supposed site of communicating nerve ; no effect as to 

 respiratory movements. 



2d. Section of both inferior laryngeal nerves ; no further effect of any permanent 

 nature. 



3d. Section of left superior laryngeal nerve; paralysis of left glottic lip. 



4th. Section of right superior laryngeal nerve; complete paralysis of glottis 



