CHAP, ii.] RESPIRATION. 439 



cartilages, assisted perhaps by the compressores naris. This 

 movement of the nostrils, perceptible in many people even during 

 tranquil breathing, becomes very obvious in laboured respira- 

 tion. 



When the mouth is closed, the soft palate which is held some- 

 what tense, is swayed by the respiratory current, but entirely 

 in a passive manner, and it is not until the larynx is reached by 

 the ingoing air that any active movements are met with. When 

 the larynx (the details of which we shall have to deal with at 

 a later part of this work) is examined with the laryngoscope, 

 it is frequently seen that, while during inspiration the glottis 

 is widely open, with each expiration the arytenoid cartilages 

 approach each other so as to narrow the glottis, the cartilages 

 of Santorini projecting inwards at the same time. Thus, syn- 

 chronous with the respiratory expansion and contraction of the 

 chest, and the respiratory elevation and depression 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 breath- 

 ing. Indeed in the latter case it is frequently absent. The 

 manner in which this rhythmic opening and narrowing is effected 

 will be described when we come to study the production of the 

 voice. Whether there exists a rhythmic contraction and expan- 

 sion of the trachea and bronchial passages, especially the smaller 

 and more exclusively muscular ones, effected by means of the 

 plain muscular tissue of those organs and synchronous with the 

 respiratory movements of the chest, is uncertain. 



