Syinptoiiis. 



109 



so very uncommon. The original change in sound over the 

 lower portion of the thorax may gradually extend up to the 

 vertebral column, or the change in intensity or timbre of the 

 sound may occur exclusively on the posterior or upper pul- 

 monary boundary and then may change in a manner already 

 indicated (see Fig. 12). 



During the initial stage of the disease auscultation reveals 

 intensified and rough vesicular breathing on account of the 

 swelling of the bronchial mucosa and of the accelerated respira- 

 tion ; even then high and crepitant rales may, however, be 

 heard, especially during inspiration, indicating the presence 

 of a serous, thick exudate in the alveoli and bronchioles. When 



Fig. 12. Croupous pneumonia with an aty])i('ai location, a, area of dullness over 

 the most posterior and upper portions of the lungs; i, area of a high, and c, 

 area of a low tympanitic sound. 



a tympanitic or weak percussion sound is audible, bronchial 

 respiratory sounds are usually heard, and frequently also 

 metallic rales. If the area of dullness becomes larger and the 

 lumen of the smaller bronchi also becomes filled with an exudate 

 there is usually an absence of all breathing sounds. Even in 

 these cases, however, one usually hears bronchial breathing at 

 the boundary of the area of dullness and further upward, be- 

 cause the hepatization of the lung reaches higher up in the 

 deeper than in the more superficial portions of the lungs and 

 bronchial breathing is conducted through the overlying, air- 

 containing layers and is heard on auscultation, while percussion 

 makes the air column in the outer strata vibrate; hence there 

 is no dullness. 



