MODIFIED RESPIRATORY MOVEMENTS. 345 



MODIFIED MOVEMENTS OF THE RESPIRATORY MUSCLES. 



Besides the ordinary respiratory motions and the voluntary 

 modifications made use of in speaking and singing, etc., the mus- 

 cles of respiration perform a series of movements of an involun- 

 tary reflex nature indicative of certain emotions and mental 

 states. 



They will be seen to resemble each other in the mechanism of 

 their production, though differing essentially in expression. The 

 following are the more important : 



Coughing is caused by a stimulus applied to certain parts of 

 the air-passages, but more particularly to the larynx ; the stimulus 

 passing along the superior laryngeal branch of the pneumogas- 

 tric. It consists in a deep inspiration, closure of the glottis, and 

 then a more or less violent expiratory effort, accompanied by 

 two, three, or more sudden openings and closures of the glottis, 

 so that rapidly repeated blasts of air pass through the upper air- 

 passages and mouth, which is generally held open. 



Sneezing is caused by a stimulus applied to the nose or eyes, 

 the impulses being carried to the respiratory centre by the nasal 

 and other branches of the fifth nerve. It consists of a deep in- 

 spiration and closure of the glottis, followed by a single explo- 

 sive expiration and sudden opening of the glottis and posterior 

 nares. 



Sneezing is a purely reflex act, it being impossible to produce 

 it voluntarily, except by the stimulation of the nasal mucous 

 membrane with some irritating substance. 



Laughing consists in a full inspiration, followed by a long series 

 of very short rapid expiratory efforts. The facial muscles are at 

 the same time thrown into a characteristic set of movements. 



Crying is made up of a series of short sudden expirations, ac- 

 companied with peculiar facial contortions, and commonly follow- 

 ing or associated with the following : 



Sobbing, which consists of a rapid series of convulsive inspira- 

 tory efforts, causing but little air to enter the chest, and followed 

 by one Jong expiration. 



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