ON DISEASES OF THE LUNGS IN HORSES. 
217 
sides, this rale is audible in inspiration alone, which at once distinguishes it 
from bronchial respiration. The crepitous rale has two modifications, import¬ 
ant 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 b}’ the inflation 
and compression of the cellular membrane of horned cattle. This is called 
the dry crepitous rule^ or crepitation. On occasions, however, the crepitous 
rale possesses a degree of softness or humidity which renders it comparable 
to the cracking 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 observable in interlobular 
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 inflamma¬ 
tion 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 had been set up. In this last case the crepit¬ 
ous rale often continues; in the former one, it ceases. This rale is likewise 
manifest in intense bronchitis accompanied with some slight parenchymatous 
inflammation: w’e have often produced it also in injecting an irritating fluid 
into the bronchia. 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 answ'er—without entering into any minute and 
useless explications—that its source is the minute divisions of the bronchia 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 distention of the cells. 
Dry SiniLOUs Rale, or Sibilation. —We have already observed, in speak¬ 
ing of the dry and mucous rales, that these sounds were the result either of 
the collision of air with some obstacle in the bronchial tubes, or of its rapid 
expulsion out of the air-cells. The sibilous rale issues from the bottom of 
the air-cells, and constitutes a shrill, dry, hissing sound, more or less prolonged 
and permanent. This rale is heard in pulmonary emphysema, both vesicular 
and interlobular, with dilatation of the extreme bronchia; and particularly 
during deep and distressful expiration. Its resonance through the bronchial 
tubes gives it strength and duration. At the entrance ( f the chest the rale 
becomes a grave sound, in the larynx and nasal cavities a shrill one; and 
in the open air is audible enough at a distance from the animal. Its inten¬ 
sity, doubtlcs.s, depends upon the extent of enlargement the bronchial tubes 
undergo. Many beginners in auscultation are apt, in large animals, to con¬ 
found this rale with the nasal, laryngeal, or bronchial sibilation: careful ex¬ 
ploration of the chest will prevent this mistake; inasmuch as the sound will 
always be found to be accompanied by the dry crepitous nilc, by bronchial 
respiration of a very loud character, and by catching of the breath. 
(’avernous Rale. — '1 his rale, as is indicated by its name, can only pro¬ 
ceed from some anorinal cavity or cavern within the substance of the lung, 
communicating with the bronchial tubes, and admitting air from them: this 
last condition being indispensable. Should the cavern contain any fluid, the 
air pa.Msiiig through it occasions gurgling or more or less ebullition, compar- 
abh? to the noise produ(ud by a current of air through a tube into a fluid in 
a vess(fl, from which it can only escape in part. 
This rumhlinp, w liicfi itself constitutes ihc eucernous rule., is the inort^ dis- 
tUKily audible the in(»re caj)acious the cavern is, and the nearer it i^ si- 
