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ILLUSTRATED STOCK DOCTOR. 
The exudation into the interlobular tissue, the congestion of the lung 
tissue itself, and the implication of the lung covering, are secondary phe- 
nomena. In other words, the disease begins where the inspired air must 
lodge the germs. Thus the inoculation of the virulent lung products on 
distant parts of the body of a sound beast rarely determines the character- 
istic lesions in the lungs, in lieu of which it induces in the seat of inoculation 
an exudation less abundant, as might be expected from the greater density 
and resistance of the integument, but which can, like the morbid lung 
products, be inoculated on sound animals with protective effect. It seems 
probable that the poison is multiplied in both cases, but that the special 
loose and susceptible texture of the lung renders its production incompar- 
ably more abundant, as the continuous ingress and egress of air through 
the diseased organ renders it immeasurably more infecting. 
How Long a Diseased Animal is Infectious. 
Proof is wanting as to the infectious nature of the disease during the 
incubative stage. If negative evidence were of any value in a case like 
this, it would be easy to adduce cases in which the removal of an animal 
as soon as it showed symptoms of the plague had apparently saved the 
rest of the herd. In other cases, the malady has been eradicated from a 
herd by careful watching, and the prompt removal of every animal as 
soon as sickness appeared. The period of greatest virulence is that at 
which the fever runs highest and when the lung is being loaded with the 
morbid exudation. 
But it must not be inferred that with the subsidence of the fever the 
danger is removed. It is a matter of every day observation that animals 
which have passed through the fever, that are now thriving well, or giving 
a free supply of milk, and to ordinary observers would appear in perfect 
health, retain the power of transmitting the disease to others. This may 
continue for three, six, nine, twelve, or, according to some, even fifteen 
months after all signs of acute illness have disappeared. This is easily 
explained. The tendency of the disease is to interrupt the circulation in 
the most severely affected parts of the lungs ; the exudation around this 
becomes developed into a tough fibrous envelope, which closes off the 
dead mass from the adjacent lung and from all communication with the 
external air. The dead and imprisoned mass now undergoes a process of 
breaking down, liquefaction, and absorption, commencing at the surface, 
and slowly advancing towards the centre. The encysted portion of the 
dead lung is one mass of infecting material, and as it undergoes no change 
except that of liquefaction, and exhales at no time any putrid odor, it re- 
mains infectious so long as it retains the solid form. At the outset more 
Hum half a lung may be thus encysted, and five or six months after alleged 
