108 
J. LAW. 
The premises become infected, and the animals may carry the 
infection on the surfaces of their bodies as well as in the lungs. 
4th —Inoculation with Weakened Virus .—The application of 
the method of Pasteur, of inoculation with attenuated virus, is 
advocated by some, but it is liable to all the objections urged 
against the simple inoculation. The attenuated virus is weakened, 
not sterilized the germs continue to propagate the kind, and as 
their virulence has been lessened by culture under certain condi¬ 
tions, it follows that it may be again increased under conditions 
of an opposite kind. All measures which owe their efficacy to 
the propagation of the disease-germ which we seek to destroy, 
are to be deprecated, where more judicious measures of extinction 
can be adopted. 
5th —Inoculation with Sterilized Virus .—Two years ago I 
was led by my study of the manifestations of lung plague in 
the system to suspect that the immunity after a first attack of 
lung plague was acquired, not by contact of the living germ with 
the lung tissue, but by its chemical products or excretions. 1 
accordingly took measures to kill the germ without altering the 
chemical conditions of the virulent fluid, and inoculated the ster¬ 
ilized liquid on the susceptible animal. In the animals into which 
this liquid was injected there occurred no local swelling such as 
results from the inoculation with the living germs, and no one of 
these animals had local swellings when afterward inoculated with 
fresh virus containing living germs, nor had any lung plague, 
when exposed for six months in infected herds and premises. On 
every occasion, when isolated, the animals thus protected by inoc¬ 
ulation with fresh virus, I took the precaution of inoculating at 
the same time an unprotected subject, and in every such animal 
the disease appeared in a characteristic form and, when the inoc¬ 
ulation had been made in the soft loose tissues of the flank, in a 
fatal one. I have since learned by experiments on animals 
that had stood some time in infected buildings, that this inocula¬ 
tion with sterilized lymph is not protective of animals that have 
already taken the germs into their lungs. To be effective it 
must be practiced on cattle before they have been exposed to con¬ 
tagion, and its efficiency will be enhanced by a repetition after an 
interval of a week or longer. 
