kKSI'IKAIK'N 



depress them, arc the muscles which act when violent 

 expiration takes pla< e ; all these muscles cause, when they 

 contract, a diminution in the size of the thorax. If the hand 

 is placed on the abdomen when a rou^h is made, the muscles 

 of the abdominal wall will be felt to become hard and tense as 

 they suddenly contract and press on the abdominal contents. 

 A cough is a strong expiration which suddenly bursts upon 



Fl(">. 58. I>iagram to show the < han^cs in the sternum, diaphragm, ami 



.iUlMinin.il wall in respiration. 



. I, iiispir.iiion ; /', expiration ; Tr, trachea; St, sternum; /', diaphragm ; At, 

 alxJumin.il wall. The shaded part is to indicate the stationary air. 



the closed glottis. The strong expiration is preceded by a 

 deep inspiration. Sighing is a deep inspiration, followed by 

 a gentle expiration. Sneezing is produced by a sharp 

 expiration, the air being driven out through the nasal passages, 

 the passage from the pharynx to the mouth being closed by 

 the descent of the soft palate towards the bark of the tongue 

 and the approximation of the pillars of the fauces. 



