395 



is continuous, and rather increases in intensity from its com- 

 mencement to its termination ; ending abruptly, like the 

 tracheal inspiratory sound. The sound is produced in part 

 by the movement of air in the small bronchial tubes, but 

 chiefly by the expansion of the innumerable air-cells of the 

 lungs. It is followed, without an interval, by the sound of 

 expiration, which is shorter, one-fifth to one-fourth as long, 

 lower in pitch, and very much less intense. A sound is not 

 always heard in expiration. In fifteen examinations record- 

 ed by Dr. Flint, five presented no expiratory sound. 



The variations in the intensity of the respiratory sounds 

 in different individuals are very considerable. As a rule 

 they are more intense in young persons; 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 are generally more intense in females than in 

 males, particularly in the upper regions of the thorax. 



It is difficult by any description or comparison to convey 

 an accurate idea of the character of the sounds heard over 

 the lungs and air-passages ; and it is superfluous to make the 

 attempt, when they can be so easily studied in the living 

 subject. 



Coughing, Sneezing, Sighing, Yawning, Laughing, Sobbing, 

 and Hiccough. 



These peculiar acts demand a few words of explanation. 



Coughing and sneezing are generally involuntary acts, 

 produced by irritation in the air-tubes or nasal passages; 

 though cough is often voluntary. In both of these acts there 

 is first a deep inspiration, followed by 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 are frequently expelled in violent 

 fits of coughing. In hypersecretion of the bronchial mucous 



