214 
ON DISEASES OF THE LUNGS IN HORSES. 
admits of satisfactory explication of these modifications. If in young animals 
the air-ceUs are more numerous and smaller, the sound ought to be stronger, 
from its entering into more places and through more circuitous routes. If, on 
the contrary, as in the old, the air-cells are larger and less numerous, there 
must be less dilatation, and more free passage of air, and consequently less 
sound. Laennec’s explanation is different from this. He supposes the air- 
cells not to be capable of equal expansion in the adult animal from their sides 
becoming hard. The feeble murmur heard in pulmonary emphj’^sema, wherein 
the air-cells are dilated or distended, favours our view of the question. In 
fat animals, cart-horses especially, and such as are of a lymphatic tempera¬ 
ment, whose chests are covered with thick skins and abundance of cellular 
substance, the respiratory murmur is scarcely perceptible. In these cases, 
one must have recourse to exertion. Drs. Chomel and Beau, the last in par¬ 
ticular, have a notion that the murmur is produced by the reflection of the 
shock the column of air receives against the fauces or glottis, back into the 
ramifications of the bronchia. But how can such a theory explain the supple¬ 
mentary murmur in one lung when the other is hepatized, unless it be by a 
sound more vesicular—stronger—in the healthy lung ; and in the superior part 
of the lung when the inferior is no longer permeable to air. Besides, if trache¬ 
otomy is performed, and afterwards the nostrils sewn up, the murmur is still 
heard, although the animal is respiring through an aperture below the place 
where, according to M. Beau, the collision happens which produces the sound 
in question. The respiratory murmur wiU be found to vary according to the 
region of the chest auscultated. In the middle region it is heard distinctly 
behind the shoulder, increasing a little thence to the ninth rib, afterwards 
gradually decreasing to the last. Along the superior region the sound is quite 
distinct, as well as below and behind the cartilage of the scapula—behind a 
mass of fat lodged there in fat subjects. At this place we have invariably 
found the murmur louder than elsewhere, and we ascribe this to the passage 
of the ^ir through the larger divisions of the bronchia, they being situated 
hereabouts : to it we give the name of hroncliial respiration; making a dis¬ 
tinction between it and the murmur. Along the inferior region, the respira¬ 
tory murmur again becomes distinct enough from behind the elbow to the 
ninth rib; whence it diminishes to the seventeenth, and is there lost. The 
sound is the same on both sides, with the exception of the place on the left 
side which receives the heart’s pulsation. We must take care not to confound 
the slight crepitating noise occasioned by the subcutaneous cellular tissue— 
which is called the dry crepitous rale —with the murmur. We must also 
distinguish the sounds of the bowels, which are characterized by their travel¬ 
ling about from place to place. 
Morbid Sounds. —Disease modifies the healthy sound in such a manner 
that the murmur may become diminished., extinct., augmented., attended or su¬ 
perseded by other sounds. 
Diminished Murmur. — Accumulated mucus within the large bronchia— 
as in bronchitis—may temporarily lessen the murmur, though it returns after 
expectoration. Capillary congestion within the parenchyma, before the onset 
of inflammation, equally occasions a considerable diminution of the respira¬ 
tory murmur, speedily succeeded by the crepitous rale, should the inflamma¬ 
tion continue. The diminution may be partial or general : rarely the latter. 
Acute enteritis and peritonitis, and in general all violent abdominal pains 
accompanied with a short quick respiration, occasion a notable diminution of 
the murmur. The same remark applies to all maladies about to end in death. 
Absence or Murmur is owing, in certain conditions of the lungs, to the 
non-penetration of air into the air-cells. This may be the result, 1st, of 
effusion into the parenchyma ; '2dly, of induration ; 3dly, of the presence and 
