OBTAINING ARTIFICIAL AGGRESSINS 39 



cm. in length which is then shaped into a triangular form. While still 

 red hot, this triangular loop should be introduced in the flask and allowed 

 to cool there. Before the culture is spread, it is advisable to bend the 

 entire loop to a slight angle by pressing it against the upper wall of the 

 flask, thereby preventing the hot end of the loop holder from coming in 

 contact with the agar surface. It is best also to test the platinum loop 

 upon the surface of the agar in order to ascertain whether it is still too hot. 



After twenty-four hours of incubation there is usually a pronounced 

 growth upon the plates. This culture is then washed off either by serum 

 or distilled water (" serous" or " aqueous aggressin"). The former may 

 be obtained fresh from a rabbit. Usually 10 to 12 c.cm. of fluid per flask 

 is required; 3 or 4 c.cm. are first poured upon the culture growth and the 

 mass scraped gently but quickly with the triangular loop. Then the 

 remainder of the fluid 7 to 8 c.cm. is poured in to release the still adherent 

 bacteria. The turbid milky emulsion is collected either in a small dark 

 glass Erlenmeyer flask or a brown bottle. This is then placed into a proper 

 apparatus and shaken for one to two days at room temperature. Enough 

 5 per cent, carbolic acid is added to make a 1/2 per cent, phenol solution, 

 and the emulsion is centrifugalized and sterilized in the same manner as 

 has been described for the natural aggressins. 



The tendency of aggressins toward increasing virulence ("infektions 

 bef orderung ") is the same whether these aggressins are artificial or natural. 



From the following experiment it can be seen that the bacteria contain 

 some substance which is easily soluble in the body fluids and in distilled 

 water, and which increases the infectious nature of the respective bacteria 

 when injected simultaneously with them. In small doses, this substance 

 is not poisonous, in large doses it may be, but is not necessarily so. There 

 is no definite relation between the poisonous qualities of the aggressin and 

 its power to increase the virulence of an infection. This disproves the as- 

 sumption of some authors that the action of the aggressins is dependent 

 upon the toxicity of the endotoxins. 



