334 PROTECTIVE INOCULATIONS. 
tate was obtained by adding one part of serum to ten parts of alcohol, 
and was dried in vacuo. This dried precipitate, in doses of 0.18 to 
0.25 gramme, was dissolved in sterilized water and injected as in the 
previous experiment. Commencing on the eighth day after infection 
five or six doses were given—in all 0.9 to1.3 gramme. Allof the ani- 
mals treated recovered, while all of the control animals died. Babes 
had previously (1889) reported successful results in conferring im- 
munity upon susceptible animals by injections of blood serum from 
immune animals. 
Tizzoni and Schwartz, in pursuing this line of investigation (1892), 
report that while the blood serum of immune rabbits neutralizes the 
“fixed virus” of rabies in vitro, after short contact (five hours), the 
blood serum of immune dogs has but slight antitoxic potency. The 
immunizing substance in the rabbit serum does not dialyze, is soluble 
in glycerin, is precipitated by alcohol, and in general behaves like a 
globulin. In subsequent experiments Tizzoni and Schwartz used 
blood serum from dogs and rabbits immunized by Pasteur’s method. 
The blood was drawn from the carotid of the immune animals, and 
the serum from the same, mixed with virulent spinal marrow in the 
form of a homogeneous emulsion, obtained by crushing and pressing 
through linen. These experiments corresponded with those pre- 
viously made as to the superior antitoxic power of rabbit serum, 
which, after five hours’ contact, neutralized the virulence of the emul- 
sion of cord. By the injection of serum from an immune rabbit, in 
doses of five cubic centimetres, into the circulation of other rabbits, 
they were, as a rule, made immune. The immunizing substance 
(antitoxin) was shown by other experiments to be present only in the 
blood. Extracts from the liver, spleen, kidney, or muscles gave a 
negative result. 
In a later communication (1894) Tizzoni and Centanni give an 
account of further experiments made principally upon sheep and dogs. 
By repeated inoculations they succeeded in obtaining from these ani- 
mals a serum having an immunizing value of 1:25,000 or more, and 
from this a precipitate was obtained estimated to have a value of 
1:300,000, and which in doses of 0.23 gramme (of the dried precipi- 
tate), dissolved in five times its weight of water, ought to be a sufficient 
dose to protect a man from the development of hydrophobia after 
being bitten by a rabid animal. 
The authors named believe that inoculations with this antitoxin 
would be reliable for man, and that they would possess decided ad- 
vantages over Pasteur’s method of inoculation. These advantages are 
specified as follows: 
