SS a ow 
from those he has outlined. Noteworthy among other specific qualities 
mentioned for the aggressins is the fact that heating for one-half hour 
at 55° to 60° destroys their action, while sterilization with chloroform, 
toluol, and dilute solutions of carbolie acid weakens it. Bail found that 
injections of aggressin alone were not particularly poisonous and never 
acutely caused death in animals. In case a fatal dose had been inocu- 
lated, there was always a prolonged illness with marked loss of weight. 
Not all of the exudates he produced contain aggressin an it was found to 
vary considerably in quantity in the different ones, but was usually likely 
to be present in largest amounts in the effusions which were rich in cells. 
In his conclusions in regard to the aggressins he emphasizes the fact 
that their action can not be explained on the assumption of their being 
anti-complements or anti-immune bodies, soluble bacterial substances, 
free receptors, etc., but they must be considered as new substances which 
have heretofore been unrecognized and which are formed by the bacteria 
in the living organism during the course of the infection. 
The great practical importance of Bail’s observations, apart from their 
theoretical interest, can immediately be seen. Indeed, what he has 
maintained is that our ideas in regard to immunization with a number 
of different bacteria, and our method of obtaining immune sera, are 
erroneous; that in the production of such sera we have treated the 
animals merely with the bacteria or with bacterial products obtained in 
artificial and inanimate media, and not with the weapons by means of 
which the bacteria carry on the combat in the living body, namely, by 
means of aggressins. In this manner he claims sera to have been obtained 
which act upon the bacteria but not upon the aggressin, and he even goes 
further and states that a true immunity against the disease—that is, a 
really active serum—can only be obtained from the injection of the living 
organism under the influence of aggressin. In this manner, not an 
anti-serum against the bacillus but one against the aggressin, hence an 
anti-aggressin serum, is produced. Therefore, for the production of the 
true immunity he insists that the animal must be inoculated with ag- 
gressin—i. e., with the body fluids of an animal which has succumbed to 
the particular infection. 
As has been mentioned, the work of Bail soon attracted the attention 
of other observers, and both Wassermann and Pfeiffer published articles 
relating to his studies. Pfeiffer and Friedberger, in their recent work 
entitled “Weitere Untersuchungen Ueber die Antagonistische Wirkung 
Normaler Sera,” ® have particularly considered the statement of Bail that, 
by intraperitoneal injections of an animal exudate containing aggressin 
into a guinea pig, the action of a bactericidal immune serum introduced 
at the same time could be entirely suspended. ‘That such a suspension 
of the bacteriolytic process of an immune serum does take place within 
* Pfeiffer und Friedberger: Deutsche Medizin. Wehnschr. (1905), 31, 1145. 
