﻿• IMMUNITY RESEARCH. 353 



locally and then generally, by certain obscure, hypothetical substances 

 which he calls "aggressins." 



He states that these substances, which he occasionally refers to as 

 simple manifestations of energy, are minute particles "of a special kind" 

 thrown off or secreted by living, uninjured bacteria. These particles do 

 not come from solution of the bacteria, nor are they extracts of bacteria; 

 they are thrown off as the result of irritation, which, he claims, is a 

 very different process. He emphasizes particularly and repeatedly the 

 importance of having living and uninjured bacteria in order to obtain 

 aggressins. The aggressins are capable of promoting infection ; they may 

 be 'preformed in the bacterium, but they are active only in the infected 

 body. They are contained in the infectious exudates, such as serous 

 exudates and inflammatory cedemas, and may be recovered -by centrif- 

 ugalization and sterilization at low temperature, being found then in 

 the fluid part of the exudate. The substances are different from any- 

 thing hitherto recognized, and their peculiarities are that they promote 

 the development of an infection, and that they interfere with the action 

 of the protective body-forces of the infected host, particular^, if not 

 solely by inhibiting phagocytosis. 



The properties of aggressin may be grouped together as follows: 



1. Sterilized aggressin added to nonlethal doses of the corresponding bacillus 

 makes these doses fatal. Thus sterilized typhoid aggressin added to a nonfatal 

 dose of typhoid bacilli and inoculated, causes death. This action is apparently 

 a stimulation of the bacteria so that they produce toxins. Apparently he does 

 not distinguish between promotion of infection due to stimulation of the bacteria, 

 and that due to inhibition of the protective mechanism of the host. 



2. Fatal closes of bacteria act more severely and acutely upon the addition of ag- 

 gressin. 



3. Inoculations of aggressins into the peritoneal cavity suspend the action of a 

 bacteriolytic serum introduced at the same time. 



4. Inoculations of aggressin confer immunity which is entirely different from 

 bactericidal immunity. 



5. Heating for one-half hour to a temperature between 55° and 60° destroys 

 aggressin, sterilization with chloroform, toluol, or dilute carbolic acid weakens it, 

 and the centrifugated aggressin exudate is to be sterilized by heating to 44° in 

 order to preserve it for future use. 



6. Injections of aggressin alone are only slowly poisonous, and never acutely 

 fatal. 



7. A fatal dose produces a prolonged illness, with emaciation preceding death. 

 • 8. Not all exudates contain aggressin, and it varies considerably in quantity in 

 different exudates, which otherwise appear identical. 



9. The aggressin is usually most abundant in exudates which are rich in cells. 



10. Aggressins vary according to their age and mode of production, and it is 

 possible, by means of serial inoculations, to increase the aggressive action of suc- 

 cessive exudates very considerable', although a point is finally reached at which 

 the series may suddenly terminate. 



11. Aggressins with bacteria block phagocytosis — that is, tbey are negatively 

 chemiotactic — but aggressins alone act very slightly. 



