OBTAINING ARTIFICIAL AGGRESSINS. 37 



this triangular loop should be introduced into 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 uncovered 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 Fy serum 

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

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

 required; 3 or /J.C.G. 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.c. is poured in to release the still adherent bacteria. 

 The turbid milky emulsion is collected either in a small dark glass Erlen- 

 meyer flask or a brown bottle. This is then placed into a proper apparatus 

 and shaken for one to two days at room temperature. Enough 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 towards increasing virulence ("infektions 

 beforderung ") 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 has a proclivity toward increasing the infectious nature of 

 their 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 quali- 

 ties of the aggressin and its power to increase the virulence of an infection. 

 This disproves the assumption of some authors that the action of the ag- 

 gressins is dependent upon the toxicity of the endotoxins. 



