MEDIATE CONTAGION IN PLEURO-PNEUMONIA 
73 
air which they contain, with impunity, and that disease cannot 
be produced in that way. It does not appear to me that these 
statements are consistent with each other. 
Dr. Gadsden quotes the letter of Prof. Axe to show that the 
contagion of lung plague is peculiarly unstable, and yet no one 
has insisted more strongly on the peculiar stability of this virus 
than has Dr. Gadsden himself, in his papers on the danger from 
chronic cases. If chronic cases are dangerous for six, twelve or 
eighteen months, then the virus is peculiarly stable. If in such 
cases it continues to exist inside of the cyst, shut off completely 
from the living tissues of the body, then we must admit that it 
would exist as well in the cyst, if this were taken out of the ani¬ 
mal and maintained under the same conditions of warmth and 
moisture. And if the breaking of a cyst inside the lungs liber¬ 
ates the contagion and allows it to disseminate into the air with 
which it comes in contact, why would not the breaking of a cyst 
outside of the body, where it is in much freer contact with the 
air, produce a like result ? Why would not this infectious 
material, if dried, pulverized, mixed with the air and inhaled, pro¬ 
duce the disease? 
The indications are that this virus is not peculiarly unstable. 
The practice of inoculation has demonstrated for us that the 
serum from the lungs retains its infecting properties for a consid¬ 
erable time, and if putrefaction is prevented by the addition of 
salt jr glycerine, it produces the typical effect in inoculations after 
weeks or even months. If it produces the lesions of the plague 
in the tail after that time, why would it not do so in the lungs if 
by any chance it reached them ? 
So far as I can see the facts are all against this theory that 
cohabitation is necessary for the propagation of pleuro-pneumonia. 
But the facts are discarded and a theory has been built up on 
negative evidence alone. Is that science? Is it a safe founda¬ 
tion on which to base our measures of eradication ? I believe 
not, and I demand better evidence before I stop disinfection and 
permit new herds to be placed in stables after infected ones have 
been removed. 
