368 PROTECTIVE INOCULATIONS. 
Chantemesse and Widal (1888) first showed by experiment that 
susceptible animals could be made immune against the pathogenic 
action of this bacillus by the subcutaneous injection of sterilized cul- 
tures. Having found that four drops of a bouillon culture, three 
days old, injected into the peritoneal cavity of white mice caused the 
death of these animals within thirty-six hours, they proceeded to in- 
ject small quantities (one-half cubic centimetre) of a culture which 
had been sterilized by heat, and found that after several such protec- 
tive inoculations the mice no longer succumbed to infection by an 
unsterilized culture. 
In experiments made upon rabbits, Bitter (1892) arrived at the 
conclusion that the immunity which he produced in these animals by 
the intravenous injection of concentrated sterilized (by filtration) cul- 
tures was due to the presence of an antitoxin in the blood of the 
immune animals. Having found that control animals were killed by 
intravenous injections of one cubic centimetre of his concentrated 
solution of the products of the typhoid bacillus, he added to twice 
this amount of the toxic solution a certain quantity (?) of blood 
serum from an immune rabbit, and injected the mixture into the 
circulation of rabbits with a negative result. Control experiments 
in which the toxic solution was mixed with L.ood serum from non- 
immune animals showed that this had no antitoxic effect, and the ani- 
mals died. Bruschettini obtained (189%) similar results in his ex- 
periments upon rabbits with cultures sterilized by heat (60° C.). He 
concludes from his experiments that the blood serum of rabbits im- 
munized in this way not only possesses antitoxic properties, but that 
it has greater germicidal potency for the typhoid bacillus than the 
blood of normal rabbits. 
Stern (1892) has made experiments to determine whether the blood 
of recent convalescents from typhoid has greater germicidal power 
for the typhoid bacillus than that of other individuals. The result 
showed that the blood serum from persons who had recently recovered 
from typhoid fever had no increased germicidal power, but rather 
showed diminished potency for the destruction of typhoid bacilli. 
But blood from a man who had suffered an attack seventeen and a 
half years previously was found to have unusual bactericidal power, 
although it did not protect white mice from typhoid infection. On 
the other hand, blood from recent convalescents served to immunize 
white mice, thus indicating the presence of an antitoxin. This is 
also shown by the experiments of Chantemesse and Widal (1892), 
who report their success in immunizing susceptible animals by in- 
jecting the blood serum of other animals previously made immune by 
