ON DISEASES OF THE EHnGS IN IIORSKS. 
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The Sound obtained by Percussion is loudest, in the middle region, be¬ 
tween the 7th, 8th, and 9th ribs. From this to the 15th rib it diminishes ; 
but again increases from this all the way to the last rib. Along the right 
superior region the sound grows louder from the posterior border of the 
shoulder to the last rib; whilst on the left side it gradually diminishes along 
the same line. This difference cannot be explained but from the circum¬ 
stance of the arch of the colon projecting so far into the chest, it being par¬ 
ticularly observable in long-carcassed horses. It shews the incorrectness of 
Leblanc’s general rule for ascertaining the nature of sounds, viz. comparing 
those of the two sides. In the inferior region, the sound obtained upon the 
6th rib may be compaied to that of the superior region behind the shoulder; 
this holds as far as the 9th rib, from which point to the last rib the sound 
gradually lessens, until it becomes abdominal. On the right side the sound 
becomes somewhat duller, on account of being opposed by the liver. After 
all, however,—what with the shoulder and the different muscles clothing the 
chest, and the cartilages of the ribs, which themselves afford little or no 
sound,—there is really not more than a third of the chest of the horse avail¬ 
able for the purposes of effectual percussion; a fact which may very well ex¬ 
plain the little advantage veterinarians have hitherto derived from the practice 
of it. The chests of old animals afford more sound than those of middle age, 
and these latter than those of young subjects: differences owing to diminished 
density of lungs and more stability of rib in the aged animal. Lean horses, 
or such as are empty-bowelled, afford more sound than fat ones, and such as 
have full stomachs. 
We are not to suppose that it is enough to have made ourselves acquainted 
with the variations of sound of the healthy chest, in order to understand those 
of disease : much practice is required to estimate the value of sounds; and, 
after aU, percussion itself is often insufficient, unaided by auscultation. 
The resonance of the healthy chest may be augmented, diminished, or an¬ 
nihilated. It is augmented throughout the posterior lobes of the lungs when 
they are emphysematous. Effusion into one pleural sac augments the sound 
of the opposite one: that lung being compelled to admit more air, becomes 
more resonant. It is diminished during congestion, inflammation of the pa¬ 
renchyma, and tuberculous phthisis, when much of the lung is diseased. The 
sound is lost or becomes dead under effusions. This deadness may be on one 
or both sides, or be conflned—as is ordinarily the case if the effusion be 
recent or inconsiderable—to the inferior part. It will increase or diminish 
according to the progress or diminution of the effusion. There is no mea¬ 
suring the effusion by sound; but we may throw it by the position of the 
animal into a place where percussion can easily detect it. M. Leblanc 
observes, that, taking want or deadness of sound to indicate the presence of 
water, the Inngs are supposed to be permeable; otherwise, the deadness 
might as much depend upon density of the pulmonary tissue as upon the pre¬ 
sence of water: still, there is a method of ascertaining from which it pro¬ 
ceeds, viz. by placing the horse in that position in which the fluid will accu¬ 
mulate in the fore part of the chest, and then, should the posterior part still 
utter a dull sound, we may conclude that the lungs are hepatized. Further- 
more, the dead sound may be partial, owing to local pulmonary condensation, 
circumscribed indurations, &c. &c. 
[To be continued.] 
