UNIVERSITY j 



RESPIRATORY SOUNDS 109 



carried on exclusively through the nasal passages, when a soft breezy 

 sound accompanies both acts. If the mouth is opened sufficiently to 

 admit the free passage of air, no sound is to be heard in health. In 

 sleep the respirations are more profound; and if the mouth is closed 

 the sound is rather more intense. 



Snoring, which sometimes accompanies the respiratory acts during 

 sleep, occurs when the air passes through both the mouth and the nose. It 

 is more marked in inspiration, sometimes accompanying both acts, and 

 sometimes it is not heard in expiration. It is not necessary to describe 

 the character of a sound so familiar. Snoring is an idiosyncrasy in 

 many individuals, although those who do not snore habitually may do so 

 when the system is unusually exhausted and relaxed. It occurs when 

 the mouth is open, and the sound is produced by vibration and a sort of 

 flapping of the velum 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 respiration. In inspiration, according to the late Dr. Austin 

 Flint, "it attains its maximum of intensity quickly after the develop- 

 ment of the sound and maintains 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 follows. This also is tubular in 

 quality. It soon attains its maximum of intensity, but unlike the sound 

 of inspiration, it gradually dies away and is lost imperceptibly. It is 

 seen that these phenomena correspond with the nature of the two acts 

 of respiration. Sounds approximating in character the foregoing are 

 heard over the bronchial tubes before they penetrate the lungs. 



Over the lungs, a sound may be heard entirely different in its char- 

 acter 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 expansion 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. 



Variations in the intensity of the respiratory sounds in different indi- 

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



