ARTIFICIAL AGGRESSINS 41 



"Artificial" Aggressins. A careful investigation of Bail's work 

 has shown that these suppositions were, after all, not well founded. 

 Wassermann and Citron have thus demonstrated that substances 

 with the identical properties of the aggressins of Bail can also be 

 obtained in the test-tube by shaking cultures of various organisms 

 (the swine plague and hog cholera bacillus, for example) with distilled 

 water, proving that the cooperation of the living organism of the host 

 is not essential. The products thus obtained, in contradistinction to 

 Bail's "natural' 1 aggressins, have been termed "artificial" aggressins; 

 there is no real difference between the two, however; the quantity 

 is smaller, but with the one as with the other it is possible to trans- 

 form subfatal doses of bacilli into fatal ones and to bring about 

 a certain type of immunity. The second assumption of Bail that 

 aggressin exudates are non-toxic has also been shown to be incorrect, 

 as the intraperitoneal injection of sufficiently large amounts of 

 dysentery, cholera, and staphylococcus aggressin in guinea-pigs will 

 not only cause general marasmus, but actually lead to the death of 

 the animal. 



In fine it has been proved (by the precipitin test, which see) that 

 aggressin exudates contain bacillary proteins, all of which possess a 

 certain degree of toxic action, and cause the formation of certain 

 antagonistic substances when injected into animals. In the light of 

 such knowledge it is now possible to account in a more natural way 

 for those observations of Bail which led him to assume the existence 

 of aggressins as substances sui generis. The facilitation of infection 

 is thus readily explained by the fact that the injection of the sub- 

 fatal dose is accompanied by the simultaneous administration of a 

 certain amount of toxic material, and not of a non-toxic substance, 

 as Bail supposed, so that death is due to the two factors directly and 

 not to the one indirectly. This, however, was nothing new in itself, 

 since Bouchard already had shown that the filtrates of various 

 bacterial cultures facilitated bacterial infection (substances favori- 

 s antes). More recently Doerr also could prove that both killed 

 cultures of various bacteria and bacterial toxins as such (diphtheria 

 and cholera toxin) are capable of producing a fatal effect when 

 injected together with subfatal doses of bacteria. 



It is also quite clear now why the simultaneous injection of cer- 

 tain bacilli together with suitable quantities of aggressin exudate 

 and corresponding bactericidal (bacteriolytic) serum does not lead to 



