110 RESPIRATION 



sons ; which has given rise to the term " puerile respiration," when the 

 sounds are exaggerated in parts of the lung in certain cases of disease. 

 The sounds usually are more intense in females than in males, particu- 

 larly in the upper regions of the thorax. 



It is difficult by any description or comparison to convey an adequate 

 idea of the character of the sounds heard over the lungs and air-passages, 

 and it is unnecessary to make the attempt, when they can be so easily 

 studied in the living subject. 



Coughing, Sneezing, Sighing, Ya^vning, Laughing, Sobbing and Hic- 

 cough. These peculiar acts demand a few words of explanation. Cough- 

 ing and sneezing usually are involuntary acts, produced by irritation 

 in the air-tubes or nasal passages, although coughing often is voluntary. 

 In both these acts, there is first a deep inspiration followed with a 

 convulsive action of the expiratory muscles, by which the air is violently 

 expelled with a characteristic sound, in the one case by the mouth, and 

 in the other by the mouth and nares. Foreign bodies lodged in the air- 

 passages frequently are expelled in violent fits of coughing. In hyper- 

 secretion of the bronchial mucous membrane, the accumulated mucus is 

 carried by the act of coughing either to the mouth or well into the larynx, 

 when it may be expelled by the act of exspuition. When either of these 

 acts is the result of irritation from a foreign substance or from secretions, 

 it may be modified or partly smothered by the will, but is not completely 

 under control. The sensibility of the mucous membrane at the summit 

 of the air-passages usually protects them from the entrance of foreign 

 matters, both liquid and solid; for the slightest impression received by 

 the membrane gives rise to a violent and involuntary cough, by which 

 the offending substance may be removed. The glottis, also, is spasmodi- 

 cally contracted. 



In sighing, a prolonged and deep inspiration is followed with a rapid 

 and usually an audible expiration. This occurs, as a rule, once in five 

 to eight respiratory acts, for the purpose of changing the air in the lungs 

 more completely, and it is due to an exaggeration of the cause that 

 gives rise to the ordinary acts of respiration. When due to depressing 

 emotions, it has the same cause ; for at such times respiration is less 

 efficiently performed. Yawning is an analogous process, but it differs 

 from sighing in the fact that it is involuntary and can not be produced 

 by an effort of the will. It is characterized by a wide opening of the 

 mouth and a profound inspiration. Yawning commonly is assumed to 

 be an evidence of fatigue, but it often occurs from a sort of contagion. 

 When not the result of imitation, it has the same exciting cause as sigh- 

 ing deficient oxygenation of the blood and it is followed with a sense 

 of satisfaction, which shows that it meets some decided want on the part 

 of the system. 



