108 



Croupuus Pueumuiiia. 



line. It usually extends backward from the elbow and readies 

 to the middle or even to the upper third of the thorax. Usually, 

 although not always, the upper boundary line describes a curved 

 line, with tlie convexity above, or descending l)ackwards (see 

 Fig. 11). It remains unchanged for three to five days, when 

 the sound again assumes a tympanitic timbre, later on it be- 

 comes purely t^mipanitic and then gradually changes again into 

 a normal, loud, non-t^^npanitic percussion sound. The low, dull 

 sound only rarely changes to the normal without having first 

 assumed a tjanpanitic timbre. 



Deviations from the changes here described are observed. 

 In affection of the deeper portions of the lungs the percussion 



Fig. 11. Arched boundary of area of dullness in croupous pneumonia. 



sound may either remain normal or not change until later on 

 after the inflammation has reached the external strata. 



If the consolidation of the upper boundary of the affected 

 area is confined to the deeper strata, one hears above the 

 upper boundary of dullness a tjanpanitic sound which may 

 exist for several days. If the deeper layers are consolidated 

 in such a manner that they nowhere touch tlie wall of the 

 thorax, but are separated from the wall by considerable por- 

 tions of healthy lung tissue, one hears only a tjanpanitic sound 

 during the whole course of the disease, and this changes into 

 a normal percussion sound during the stage of resolution. 

 Deviations as to the seat of the area of dullness also are not 



