THE NORMAL RESPIRATORY SOUNDS. 245 



116. The Normal Respiratory Sounds, 



Normal Vesicular Sound. If the ear directly, or through the 

 medium of a stethoscope, be placed in connection with the chest-wall, 

 we hear over the entire area, where the lung is in contact with the 

 chest, the so-called "vesicular" sound, which is audible only during 

 inspiration. It is a fine sighing or rustling sound. It is said to be 

 caused by the sudden dilatation of the air-vesicles (hence " vesicular") 

 during inspiration, and it is also ascribed to the friction of the current 

 of air entering the alveoli. 



The sound has, at one time, a soft, at another, a sharper character; 

 the latter occurs constantly in children up to 12 years of age. In 

 their case, the sound is sharper, because the air, in entering vesicles one- 

 third narrower, is subjected to greater friction. As the air passes out 

 of the air-vesicles during expiration, it gives rise to a feeble sighing 

 sound of an indistinct soft character. 



Bronchial Respiration. Within the larger air-passages larynx, 

 trachea, bronchi during inspiration and expiration, there are loud 

 sounds like a sharp h or ch the " bronchial" the laryngeal, tracheal, 

 or " tubular" sound, or breathing. This sound is also heard between 

 the scapulae, at the level of the fourth dorsal vertebra (bifurcation of 

 trachea), and it occurs also during expiration, being slightly louder on 

 the right side, owing to the slightly greater calibre of the right 

 bronchus. 



At all other parts of the chest, the vesicular sound obscures the 

 tubular or bronchial sound. If the air-vesicles are deprived of their 

 air, the tubular breathing becomes distinct. It is asserted that, when 

 lungs containing air are placed over the trachea, the tubular sound 

 there produced becomes vesicular. In this case, we must suppose 

 that the vesicular sound arises from the tubular breathing becoming 

 weakened, and being acoustically altered, by being conducted through 

 the lung alveoli (Baas, Penzoldt). A sighing sound is often produced 

 at the apertures of the nose and mouth during forced respiration. 



117. Pathological Respiratory Sounds. 



Historical. Although several abnormal sounds in connection with diseases of 

 the respiratory organs were known to Hippocrates (succussion-sound, friction, and 

 several catarrhal sounds), still, Laennec was the discoverer of the method of 

 auscultation (1816), while Skoda greatly extended our knowledge of its facts. 



(1.) Bronchial breathing occurs over the entire area of the lung, either when 

 the air- vesicles are devoid of air, which may be caused by the exudation of fluid 

 or solid constituents, or when the lungs are compressed from without. In both 



