684 
CONSTRUCTION OF THE CAVITY OF 
the lung. Whenever this rale is clear, with metallic tinkle, 
however small, it no longer denotes simple catarrh, but 
indeed an exudative pneumonia, or an exudation that is 
recent, not having become yet solidified. Only, when there 
exist considerable productions of mucosities or frothy serum, 
can we make out the different mucous rales recognised in a 
man affected with catarrh. According to researches in 
pathological anatomy, two only of these affections are 
acknowledged in the horse : — 1 . Acute pulmonary oedema ; 
2. Enlargement of the bronchial tubes. Acute oedema of the 
lungs takes place often when there is tardy asphyxia, arising 
from mechanical impediment to respiration. Sometimes it 
comes on suddenly owing to violent efforts. In this case, 
percussion affords a full sound, clear and more elevated, the 
resonance being more prolonged. Auscultation yields sounds 
varying with the intensity of the disease ; the rale may be 
more or less intense, and may amount to little or nothing 
at a time the disease is very violent. 
Sometimes it happens that the bronchial tubes are con- 
siderably dilated ; then is discharged {per naves) a yellow 
foulness, sticking close like purulent matter, which fills the 
bronchial tubes up to the trachea. This mucus it is that 
occasions, through respiration, the different sounds of rale 
and hissing recognised in man. 
Signs of Pneumonia. — Pneumonia in animals does 
not afford diagnostic signs so clear as are heard in man. ' The 
practitioner, habituated to researches after the physical 
indications of chest diseases, will readily distinguish a simple 
pneumonia, having a certain extension from simple pleurisy 
with exudation. However, the fact already mentioned, which 
shows that inflammation often breaks out in part of the lungs 
so profound as to be inaccessible to physical inquiries, as well 
as the combination of pleurisy with the pneumonia, or where 
one is often the sequel of the other, causes the differential 
diagnostic often to be very difficult. 
M. Muller wishes it to be observed, that acute pulmonary 
catarrh affecting the air cells, is not to be distinguished by 
auscultation and percussion, from acute oedema, nor from 
pneumonia in the first stage, and that no exact difference 
is to be established even in the dead body. In the three 
cases, the signs of percussion and auscultation are the same ; 
percussion yields a clear sound and full, and over a larger 
circuit. This resonance derives something from percussion 
of the abdominal cavity. 
Auscultation in pneumonia, in its first stage, yields the 
indications of catarrh in a more marked degree ; a vesicular 
hoarse sound often extends over the entire thorax. 
