RESPIEATORY SOUNDS. 129 



pendulum palati, between the two currents of air from the mouth and nose, 

 together with a vibration in the column of air itself. 



Applying the stethoscope over the larynx or trachea, a sound is heard, of 

 a distinctly and purely tubular character, accompanying both acts of respira- 

 tion. In inspiration, according to the late Dr. Austin Flint, " it attains its 

 maximum of intensity quickly after the development of the sound and main- 

 tains the same intensity to the close of the act, when the sound abruptly ends, 

 as if suddenly cut off." After a brief interval, the sound of expiration fol- 

 lows. This is also tubular in quality. It soon attains its maximum of inten- 

 sity, but unlike the sound of inspiration, it gradually dies away and i lost im- 

 perceptibly. It is seen that these phenomena correspond with the nature of 

 the two acts of respiration. 



Sounds approximating in character to the foregoing are heard over the 

 bronchial tubes before they penetrate the lungs. 



Over the substance of the lungs, a sound may be heard entirely different 

 in its character from that heard over the larynx, trachea or bronchial tubes. 

 In inspiration the sound is much less intense than over the trachea and has 

 a breezy, expansive, or what is called in auscultation, a vesicular character. 

 It is much lower in pitch than the tracheal sound. It is continuous and 

 rather increases in intensity from its beginning 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 expan- 

 sion of the air-cells of the lungs. It is followed, without an interval, by the 

 sound of expiration, which is shorter one-fifth or one-fourth as long lower 

 in pitch and much less intense. A sound is not always heard in expiration. 



The variations in the intensity of the respiratory sounds in different indi- 

 viduals are very considerable. As a rule they are more intense in young per- 

 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 

 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 unnecessary to make the attempt, when they can be so easily studied in the 

 living subject. 



Coughing, Sneezing, Sighing, Yawning, Laughing, Sobbing and Hic- 

 cough. 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, although coughing is often voluntary. In both of 

 these acts, there is first a deep inspiration followed by a convulsive action of 

 the expiratory muscles, by which the air is violently expelled with a charac- 

 teristic 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 mem- 

 brane, 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 exspui- 



9 



