:, ) A N A T M V AND I'll VS1ULOUV U !•' 



3. Section of left superior laryngeal nerve; complete paralysis of glottis. 



Experiment. — A small snapper was secured as usual, and the hyoid apparatus 

 separated from the lower jaw and turned up for convenience of observing glottis. 

 We then cut subcutaneously the left superior laryngeal nerve, causing motion in 

 the glottic lips. This section slightly lessened the power to move the glottic lips mi 

 the side cut. We next divided, in like manner, the right superior laryngeal nerve. 

 The power to open the glottis remained but little impaired, but the air could no 

 longer be retained in the Lungs. Respiration went on as usual, but when inspira- 

 tion was complete and the muscles relaxed, the glottic lips fell together by virtue 

 of their own elasticity, although this seemed insufficient to balance the contractile 

 force of the expanded lung, whose contents therefore escaped. Then followed 

 renewed inspirator; efforts, necessitated by tin; loss of power to close the glottis, 

 until the animal learned to hold the air in its lungs by keeping tense, for a time, 

 the flank muscles of inspiration. The left and right inferior laryngeal nerves 

 having next been divided, entire paralysis of the glottis ensued, the flaccid lips 

 falling together valve-like when efforts were made to inhale air, while, if air was 

 blown into the lungs, it escaped without difficulty. 



Order <//' section, and results: — 



,. . ,. . , , ( Glottic litis convulsed 



Section ot lett superior Laryngeal. { , \ 



1 • { by section. 



... ,. . . . , , f LOSS of power to close 



Section ot right superior laryngeal. 1 . . l . 



' ) glottis firmly. 



Section of both recurrent laryngeals. j Complete paralysis of glottis; 



{ loss of power to open glottis. 



The above experiments, repeated upwards of twelve times on the Chrysemys 

 picta, the Cistudo virginea, the Chelonia mydas, and the Chelydra serpentina, left 

 no doubt in our minds as to the functions of the two Laryngeal nerves in turtles. 

 Careful dissections enabled us moreover to trace these nerves so as to show that, 

 while the inferior laryngeal is distributed only to the opening muscle of the larynx, 

 the superior laryngeal sends branches to both the dilating and the constricting 

 muscles. 



This anatomical arrangement explained to us some of the difficulties which we 

 had encountered while testing the function of the muscles by means of irritants 

 applied to the nerves. Thus, when the upper nerves were irritated, the glottis 

 opened at the outer lip and closed within, because the irritant necessarily acted 

 both on the nerve fibres of tin- closing and of the opening muscles. Again, when 

 the lower nerve, inferior Laryngeal, was galvanized, it caused the lips of the glottis 

 to open, but not freely, because the motion of the lips seemed to act reflectively as 

 a cause of irritation through the mucous branches of the superior laryngeal on to 

 its nerve centres, and thence by its motor fibres upon the opponent closing muscles. 

 When, however, the superior Laryngeal nerves were cut, the closing power was 

 abolished, and then, irritation of tin 1 inferior nerves produced more perfect dilata- 

 tion of the glottic chink. We have thus determined by every necessary means 

 that the superior Laryngeal nerves in turtles are the nerves of sensibility for the 

 mucous membrane of the Larynx and glottis. That they are the motor nerves of 



