K B S P I R A T ION I X T II E C II B LONI A. 39 



act of respiration consists of an expiration and an inspiration, during which the 

 glottis remains open. 



8th. The opening of the glottis is effected through the agency of the superior 

 and inferior laryngeal nerves, both of which are distributed to the dilating muscle 

 of the glottis. The superior laryngeal nerve presides over the closure of the 

 glottis, being in part, distributed to its sphincter muscle. The elastic contractility 

 of the glottic cartilages aids in closing this orifice. After section of the superior 

 laryngeal nerves, the glottis may still be opened by the agency of the inferior 

 laryngeal nerves, its imperfect closure being then effected by means of the elasticity 

 of its cartilaginous lips. The chiasm of the superior laryngeal nerves enables 

 one of these nerves to open and shut the glottis after section or disease of the 

 opposite nerve and of both inferior laryngeals. 



Physiologists have therefore been in error when describing the respiration of 

 Chelonians as analogous to that of Batrachians, since it far more closely resembles 

 the breathing of the higher vertebrates. 



