88 
ihe hastening power of the reaction must be regarded as an advan- 
tage that the organism has won for itself through the occurrence of 
the first disease. 
In applying this view to disease von Pirquet and Schick find that an 
organism in the stage of the free antibodies is an expression of the 
immediate power of reaction or hypersensitiveness. This stage has 
only a limited duration. The free antibodies disappear; however, 
the individual remains immune. The fact of this immunity consists, 
however, no longer in the power of immediate reaction against the 
cause of the infection, but in a hastened power of reproduction of 
antibodies. An organism has the power to combat a newly intro- 
duced infection and localize it. as is well shown in the case of vac- 
cination. Von Pirquet and Schick believe that this property does 
not depend so much upon free antibodies in the fluids as upon a 
property acquired by the cells through the first disease, in which we 
see an expression of cellular immunity. 
In TTassermann's 0 observation that the adaptation of the tissues 
to tJie existence of microorganisms which were naturally pathogenic 
without any apparent reaction and production of antibodies we see 
an instance of i mm unity through insusceptibility. 
A series of diseases — for example, smallpox, measles, varicella, 
rothlen — cause after one attack the individual to remain more or 
less protected throughout the rest of his life. Thev have the com- 
mon clinical characteristic that, after a long and definite period of 
incubation, the disease runs a course in a definite and comparatively 
short time. If the organism does not die as a result of the disease, 
then it has won a complete victory over the cause of infection: the 
same is no longer able to produce harm in such an organism. 
According to von Pirquet and Schick the fact that the clinical 
immunity against this group of diseases, for which we may take vac- 
cinia as a type, does not consist of an acquired nonsuseeptibility 
against the cause of the infection, but the power of an accelerated 
reaction. They believe they have shown from their work that they 
have reawakened interest in the serum disease and that this syn- 
drome is not only of interest clinically but. from the standpoint of 
general pathology, is of the greatest importance. 
Our explanation of the cause of sudden death following the second 
injection of horse serum does not differ essentially from the theory 
(which has just come to our notice as our manuscript is being edited 
for press published by von Pirquet and Schick, relative to the reac- 
tion of the serum disease in man, although these similar deductions 
were reached independently and from different premises. 
a W assermann. A.. Uber naturliehe und kunstliehe Immunirat. Zeir. f. Hyg.. bd. 37, 
p. 173. Wesen der defection, in Kolle und Wassermann. Handb. der pathogen. 
Mikroorganismen, 1S03. 
