64 
D. E. SALMON. 
ties have felt confident in assuming that because disease-germs 
evidently have the power of multiplying themselves indefinitely, 
when the conditions are favorable, a single one of these would 
produce the disease as certainly as a larger number, though it 
would probably require a longer period of incubation. 
Strange and inexplicable as it may appear to us, this assump¬ 
tion is not in accordance with the truth, and if the conclusions 
from all of M. Chauveau’s experiments had been as defective as 
with this series, which happily they were not, we might well have 
doubted the power of man to solve a problem so complicated and 
mysterious. 
If we examine a drop of fresh vaccine lymph, with suitable 
precautions, we will have no difficulty in deciding that it contains 
many more than fifty germs, and that, consequently, if Chauveau’s 
reasoning was correct there should have been no failures with 
dilutions of one to fifty.* Again, Chauveau’s experiments with 
diluted virus, like those of every other investigator who has at¬ 
tempted the same line of research, are unreliable and defective, 
because, first, lymph, blood, or other liquids taken from the ani¬ 
mal body contain cells, organic debris and coagula to which the 
germs adhere and which prevent their regular diffusion iu the di¬ 
luting liquid*; secondly, because the number of germs in a drop 
of lymph from different pustules, or in a drop of blood from 
different animals, varies to an extraordinary degree ; and, thirdly, 
because different animals have a different degree of susceptibilty 
in regard to the germs of the same disease. In other words, just 
as there is a vis medicatrix naturce which enables a certain 
number of the individuals in which disease-germs have multi, 
plied to overcome such germs and to recover from contagious dis¬ 
eases, so there is a vis conservatrix naturae , by which not only a 
certain number of individuals resist the germs of any given dis¬ 
ease, but which enables every individual to resist a certain num¬ 
ber of these germs. 
# I hope that the opponents of the germ theory will forgive me for assuming 
that the organisms seen in virulent liquids are disease-germs, for it would be 
manifestly impossible for me to enter into a discussion of this question in the 
present article. 
