88 DISEASES OF THE LUNGS. 



In conclusion. Bronchial respiration being a constant unequivDcal 

 sign of important pathological alteration, it is that to which the prac- 

 titioner should give his most special and undivided attention. 



Crepitous rale. — Laennec has given this appellation to a sound 

 which accompanies the respiratory murmur, and which he has compared 

 to the crackling powdered salt makes when thrown upon some burning 

 hot body, to the noise elicited by the inflation of a small dry bladder, or 

 to that produced by the compression between the fingers of a sound lung 

 distended with air. It suffices to have heard it once not to confound it 

 with the other rales ; and, besides, this rale is audible in inspiration 

 alone, which at once distinguishes it from bronchial respiration. The 

 crepitous rale has two modifications, important to be distinguished : it 

 may be dry or altogether like the crackling of the bladder, such as we 

 have described, or such as is produced by the inflation and compression 

 of the cellular membrane of horned cattle : this is called the di^y ci^epitous 

 rdle^ or crepitation. On occasions, however, the crepitous rale possesses 

 H degree of softness or humidity which renders it comparable to the 

 crackling of a bladder slightly moistened. This is less distinct than the 

 former, and has received the name of the humid crepitous rale. 



The DRY CREPITOUS RALE, or CREPITATION, is obscrvablc in inter- 

 lobular emphysema of the lung, in partial gangrene — at least, in the 

 parts surrounding the latter, and often in the extremities of the posterior 

 lobes as well. 



The HUMID CREPITOUS RALE is heard at the commencement of inflam- 

 mation of the substance of the lungs. Should all murmur cease soon 

 after, it is a sign of parenchymatous induration ; its return indicates the 

 resolution of the induration ; and should murmur be heard around a part 

 impenetrable to air, it denotes either resolution of the circumference of 

 the indurated part, or that an areola of inflammation has been set up. 

 In this last case the crepitous rale often continues ; in the former one, it 

 ceases. This rale is likewise manifest in intense bronchitis accompanied 

 with some slight parenchymatous inflammation : we have often produced 

 it also by injecting an irritating fluid into the bronchi. It is a common 

 occurrence for this rale to be indistinct: when it is so, it becomes 

 necessary only to momentarily excite the respiration to render it more 

 audible. Should we be asked the question — How this rale is produced, 

 and where ? We answer — without entering into any minute and useless 

 explications — that its source is the minute divisions of the bronchi and 

 the air-cells ; and that its occasion is, doubtless, the difficulty experienced 

 by the air in making its way through these small tubes to the air-cells : 

 added to which, it may in part arise from the distension of the cells. 



Dry sibilous rale, or sibilation. — We have already observed, in 

 speaking of the dry and mucous rales, that these sounds were the result 

 either of the collision of the air with some obstacle in the bronchial tubes, 



