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D. E. SALMON. 
with a dilution of 1 to 20, four with a dilution of 1 to 30, and 
five with a dilution of 1 to 50. The inoculations with the strongest 
virus (1 to 20) produced a general eruption, which followed the 
regular course. But with the weakest virus, injected in half the 
quantity, the effect was less marked. With live sheep inoculated 
with eight centigrammes of this dilution, a single one presented 
a very mild secondary eruption, three had a pustule at the point 
of inoculation, the fifth had only a slight swelling at this point. 
All acquired immunity. 
These experiments, like Chanveau’s, are not sufficiently nu¬ 
merous to demonstrate a great principle, but they are one more and 
a very important contribution to this end. In the methods of both 
of these gentlemen, there is much to be desired before they could 
be applied in practice, especially to such virulent diseases as fowl 
cholera, with which a single drop of a dilution of 1 to 40,000 
sometimes causes death. The strong virus which they use varies 
greatly in strength, it contains coagula and animal debris which 
prevents its even diffusion; it is in many cases difficult to obtain 
when desired. By my method the virus is obtained of a definite 
strength; it may be preserved for an indefinite length of time in 
cultivation tubes, and in a short time can be increased to any de¬ 
sired quantity. These are points which, especially in endeavors 
to control the diseases of mankind, must be considered of the 
greatest importance. 
In presenting a new method for attenuating the active viruses 
of contagious diseases it is, of course, desirable to know how it 
compares practically with the method of M. Pasteur which has 
recently received so much attention, and which, in spite of ad¬ 
verse criticism, must be accepted as a remarkable advance in 
medical science. It has not been unusual for men who stand 
quite high in scientific circles to speak of Pasteur’s method as 
though the mitigation in this case was produced by dilution ; 
others of equal eminence have told us that it consisted in passing 
the virus through a large number of cultivations. In reality, it 
is neither the one nor the other. Pasteur’s first attenuation was 
made with fowl cholera virus, and his method with the later ones 
has only been changed to suit the peculiarities of the virus of 
