CONTRIBUTION TO THE STUDY OF SWINE PLAGUE, ETC. 701 
previous inoculation of the serum of vaccinated animals. In 
a great number of other cases the resistance has been of a 
limited duration and the animals have died after a longer 
time than the witnesses, time varying from some hours to six 
days. This length of time depends on the activity of the 
serum, the dose injected, the mode of inoculation (in the vein 
or under the skin), and the space of time between the injection 
of the serum and that of the virus. In my experiments the 
injection of serum has no longer a preventive action, if the 
testing experiment was made six days after the first; the 
optimum seems to be in the first twenty-four hours, but it is 
better to wait several hours between the two injections. 
3d. The injection of serum made after that of the virus, 
when there is already an elevation of temperature, postpones 
death about in the same measure as the preventive injection. 
In increasing the activity of the serum, from these results, 
one could obtain a preventive and an efficacious therapeutic 
effect. 
4th. Animals having resisted a test of virulent culture, 
thanks to the preventive serum, have not by this fact obtained 
a lasting immunity; a second testing injection has produced 
death with a small extent of life against that of the witnesses. 
5th. Injections of small doses of serum, repeated after the 
testing injection, have seemed to me to postpone the death, 
but not in proportion to the total of the quantity injected. 
B. Pneumoenteritis .—No more than for swine plague , I have 
not here observed bactericide power m vitro; microbes of 
pneumoenteritis, left for several days in contact with the 
serum of vaccinated animals, have always given cultures; I 
have not examined if the virulency had been attenuated. 
By opposition, the preventive action has been more ac¬ 
cused than for swine plague , though it is with a microbe much 
less virulent, and that the serum that I used had been ob¬ 
tained from a rabbit vaccinated with a quantity of toxine 
relatively weak, which makes me suspect that there is yet 
another factor acting. 
The two rabbits which received injections of this serum 
survived to the test, namely: 
