§14 BACTERIOLOGY. 
to obtain the immunizing substances in a more concen- 
trated form. Fo and Scabia and F. and G. Klem- 
perer prepared glycerin extracts, after the manner of 
Koch, calling their extract “ pneumoprotein.”” At 
present, however, a protective serum is obtained from 
horses by the repeated injections of fully virulent 
pneumococci in exactly the same manner as in the pro- 
duction of antistreptococcus serum. 
Therapeutic Experiments. Curative experiments in 
man have also recently been made with the blood-serum 
of immunized animals and of persons who have recov- 
ered from an attack of pneumonia. The most success- 
ful of these were conducted by F. and G. Klemperer. 
These authors hold that in man during the pneumonic 
process there is a constant absorption into the circula- 
tion of this toxic albuminous substance produced by 
the bacteria in the lungs. This continues until event- 
ually the same antitoxic substance is produced in the 
circulation that has been seen to occur experimentally. 
It is then that the crisis occurs. The bacteria are 
neither destroyed nor is their power to produce pneu- 
motoxin lessened ; but the third factor—the antipneumo- 
toxin—now exists and neutralizes the toxic substances 
as they are produced. They apparently demonstrated 
that the serum of the blood of patients after the crisis 
of pneumonia contained antitoxic substance, and was 
capable, in a fair number of cases, of curing the dis- 
ease when injected into infected animals. They have 
made preliminary observations upon patients with a 
view of inducing the crisis by the injection of the 
blood-serum of persons convalescent from pneumonia, 
and which, consequently, contain the antitoxic body. 
In six pneumonic patients the results were promising. 
