CHAP, ii.] RESPIRATION. 325 



larynx is examined with the laryngoscope, it is frequently seen that, 

 while during inspiration the glottis is widely open, with each expi- 

 ration the arytenoid cartilages approach each other so as to narrow 

 the glottis, the cartilages of Santorini projecting inwards at the 

 same time. Thus, synchronous with the respiratory expansion and 

 contraction of the chest, and the respiratory elevation and depres- 

 sion of the alse nasi, there is a rhythmic widening and narrowing 

 of the glottis. Like the movements of the nostril, this respiratory 

 action of the glottis is much more evident in laboured than in 

 tranquil breathing. Indeed in the latter case it is frequently 

 absent. The manner in which this rhythmic opening and narrow- 

 ing is effected will be described when we come to study the pro- 

 duction of the voice. Whether there exists a rhythmic contraction 

 and expansion of the trachea and bronchial passages effected by 

 means of the plain muscular tissue of those organs and synchronous 

 with the respiratory movements of the chest, is uncertain. 



