K E S I' I I! A T I () N I S 'I' II E < ' II K L O N 1 A 35 



firmly on the right side; the right glottic lip now relied alone on the recurrent nerve 

 for opening power. 



3. Section of right recurrent (inferior laryngeal nerve); paralysis of right glottic 

 lip. 



The above stated experiments were repeated very frequently, and always with 

 the like results. If the evidence which we have given be reliable, we have now 

 proved that in turtles there exists a communication between the right and left 

 superior laryngeal nerves, of the nature of a true chiasm precisely like that of the 

 optic nerves, and, so far as we know, the only instance thus far discovered of this 

 anatomical peculiarity in nerves exterior to the great centres. 



Fig. 8. 



Fig. 8. Diagram of the chiasm of the superior laryngeal nerves. — u a', intercommunicating fibres of the right 



nerve; b', similar fibres from the left nerve. 



The diagram, Fig. 8, illustrates our views in regard to the track of the nerve 

 fibres. Part of each nerve probably proceeds directly to the two glottic muscles 

 of its own side, while another strand crosses over through the interlateral trunk to 

 be similarly distributed to the two muscles of the opposite side. 



Keeping this in view, we can now see how one single superior laryngeal nerve 

 may move the glottis on both sides, until the chiasm is divided, when it will be 

 left in connection only with the muscles on its own side of the glottis. 



Having thus established the fact of a chiasm between the superior glottic nerves, 

 it was requisite to ascertain whether the inferior or recurrent laryngeal nerves 

 entered into communication with the superior nerves, or whether they possessed 

 any similar interlateral connection of their own. 



Experiment. — Snapper, weight six pounds. We divided first the right and left 

 superior laryngeal nerves. The glottis opened as usual, but had lost its power to 

 close firmly. 



Section of the right recurrent which followed, as the next step, produced paraly- 

 sis of the right glottic lip. 



Galvanization of one recurrent caused opening of only the corresponding lip of 

 the glottis. Repetitions of the above experiment led to no different result. 



Order of section, and results: — 



1. Section of both superior laryngeal nerves; loss of closing power. 



