Chap. XIII] RESPIRATORY SYSTEM 249 



MODIFIED RESPIRATORY MOVEMENTS 



Various emotions may be expressed by means of the respira- 

 tory apparatus. 



Sighing is a deep and long-drawn inspiration, followed by 

 a sudden expiration. 



Yawning is an inspiration, deeper and longer continued than 

 a sigh, drawn through the widely open mouth, and accompanied 

 by a peculiar depression of the lower jaw. 



Hiccough is caused by a sudden iiispiratory contraction of 

 the diaphragm; the glottis suddenly closes and cuts off the 

 column of air just entering, which, striking upon the closed 

 glottis, gives rise to the characteristic sound. 



Sobbing is a series of convulsive inspirations during which the 

 glottis is closed, so that little or no air enters the chest. 



Coughing consists, in the first place, of a deep and long-drawn 

 inspiration by which the lungs are well filled with air. This 

 is followed by a complete closure of the glottis, and then comes 

 a forcible and sudden expiration, in the midst of which the glottis 

 suddenly opens, and thus a blast of air is driven through the upper 

 respiratory passages. 



Sneezing consists of a deep inspiration, followed by a sudden 

 and forced expiration, which directs the air through the nasal 

 passages. 



Laughing consists essentially in an inspiration, followed by 

 a whole series of short, spasmodic expirations, the glottis being 

 freely open during the whole time, and the vocal cords being 

 thrown into characteristic vibrations. 



Crying consists of the same respiratory movements as laugh- 

 ing; the rhythm and the accompanying facial expressions are, 

 however, different, though laughing and crying often become 

 indistinguishable. 



Speaking consists of a voluntary expiration and the vibration 

 of the vocal cords as the air passes over them. 



