276 PROTECTIVE INOCULATIONS. 
tious material introduced had previously been insisted upon by Da- 
vaine in his paper entitled “ Recherches sur quelques unes des conditions 
qui favorisent ou qui empéchent le dévelopment cde la septicémie,” pub- 
lished in the Bulletin of the Academy of Medicine, séance of February 
18th, 1879. 
Davaine says: 
“‘A third condition relates to the quantity of bacteria introduced into the 
tissues. This question of quantity has been made manifest in our experi- 
ments. Not only doesit differ in different species of animals, the rabbit and 
the dog, for example, but it varies in different animals of the same species.” 
In his communication to the Academy of Sciences, made on April 
4th, 1881, Chauveau gives the results of his experiments in producing 
immunity by inoculations with very small quantities of virus. After 
some preliminary experiments with a larger number, five sheep were 
inoculated with diluted anthrax blood estimated to contain two hun- 
dred and fifty bacilli for each. Atl of the animals survived the inocu- 
lation after having manifested some slight febrile reaction. Six weeks 
later all were reinoculated with a dose which should have been fatal 
to an unprotected animal. One of the animals died of anthrax, the 
other four resisted perfectly. 
On June 26th, 1882, Chauveau reported to the Academy of Sciences 
the results of his experiments relating to the protection of animals 
from anthrax infection by the method of Toussaint. By carefully 
conducted experiments Chauveau found that nine or ten minutes’ ex- 
posure to a temperature of 54° C. killed all of the bacilli in anthrax 
blood, and the same result was obtained by sixteen minutes’ exposure 
to 52° C., while at 50° C. the time required is twenty minutes. An 
attenuated virus suitable for protective inoculations is obtained by 
exposure for a somewhat shorter time, and as a result of his experi- 
ments Chauveau was led to the conclusion that for a first inoculation 
anthrax blood heated to 50° C. for fifteen minutes afforded a good at- 
tenuated virus. This was to be followed after an interval of ten to 
fifteen days by a second inoculation with a stronger virus, obtained 
by exposing anthrax blood to the same temperature (50° C.) for nine 
or ten minutes. These inoculations sufficed to protect the animals 
when they were subsequently inoculated with virus of full strength— 
blood from an animal which had recently succumbed to the disease. 
Chauveau says with reference to this method: 
‘‘In one hour, with a single guinea-pig [dead of anthrax], it is easy to 
prepare the quantity of vaccine required to inoculate more than five hundred 
sheep. The inoculation is made with the point of a lancet, charged, by the 
method in use in my: laboratory, with a very small quantity of virus. Two 
