PLEUROPNEUMONIA. 
829 
colour is deeper, the diseased portion is slightly swollen 
and, when it is cut, numerous minute spots of blood suddenly 
appear on the cut surface. No interlobular exudation may 
have taken place, but the morbid changes will be, neverthe- 
less, sufficiently definite in character to enable the observer 
to detect an exact line of demarcation between the healthy 
and diseased lung tissue even at this early period of the dis- 
ease. 
By a very gradual, and probably continuous process of 
development, the lesions become more and more defined. 
The colour of the lung gets darker, until it reaches a deep 
purple, or nearly black tint ; exudation of the serous fluid 
from the distended vessels fills the meshes of the fibrous 
tissue between the lobules; the diseased part which is often 
the greater portion of one lung increases in size day by day ; 
the fluid exudation is constantly being squeezed out of the 
coagulating solids and falls to the bottom of the cavity of the 
chest ; and at length the animal dies from exhaustion, or the 
virulence of the affection is expended, and the morbid action 
is arrested, leaving a large portion of the lung in a state of 
permanent disorganisation. 
The rate of progress of the disease will depend upon the 
age and condition of the subject, as well as upon the acute- 
ness of the attack ; but some idea of the ordinary course of 
the malady may be gained by reference to a recent case which 
was carefully watched to its termination. The animal, a 
milch cow, was one of four in the same shed, and did not 
present any peculiar symptoms; it may, therefore, be con- 
sidered that the deposit advanced at the average speed. 
Only one lung w as diseased, and the observation was com- 
menced when a small portion of the lower border of the 
organ was affected. Auscultation and percussion were em- 
ployed two or three times a week, and the gradual extension 
upwards of the disease was very easily traced. At the end 
of the third w’eek of observation, or about a month from the 
first appearance of signs of the affection, the whole of the 
right lung was in a state of consolidation, and the animal 
was destroyed. When removed from the chest, and discon- 
nected from the windpipe and large vessels, the diseased 
lung weighed forty-eight pounds, the healthy organ of the 
opposite side weighed nine pounds. 
Enlargement of the lungs, or portions of the lungs, as the 
result of deposit of new material in the spaces between the 
lobules and upon the surface is a speciality of pleuropneu- 
monia. The malady may be distinguished with absolute cer- 
tainty by this single morbid change, which bears no resem- 
xliv." J ' 57 
