110 ACTIVITIES OF BACTERIA. 



certain whether a man has had (Gruber and Durham) or 

 still has (Vidal) typhoid fever, if it is demonstrated that 

 the serum from a blood specimen in a dilution of -^ causes 

 marked agglutination of true typhoid bacilli, while it is 

 without effect upon closely related organisms (Bact. coli). 

 (For further details see special part.) 



In conclusion, we may say that the essential separation 

 of immunity into antitoxic and bactericidal appears to- 

 day to be entirely warranted, but that in a series of cases 

 it is established that not infrequently antitoxic and bac- 

 tericidal immunity are both present. Brief reference was 

 made above to the fact that strong diphtheria antitoxin 

 has also some bactericidal action (van de Velde). Wasser- 

 mann found that an animal protected against pyocyaneum 

 poison also tolerates the virulent Bact. pyocyaneum in 

 large doses, and other similar experiences are contained 

 in the literature (compare under Cholera). 



APPENDIX. 



According to investigations by Emmerich and Low which 

 have just appeared (end of May, 1899) (Z. H. xxxi, 1), 

 the whole doctrine of the bactericidal action of the body 

 fluids and the immunity depending thereon appears in a 

 surprisingly . altered light. 



In every old culture of bacteria, according to the 

 authors, there are found bacteriolytic, remarkably heat- 

 resisting enzymes i. e.j ferments, which are able to dis- 

 solve and kill bacteria, especially old cells. Agglutination 

 is only the first stage of the solution and depends, as Gru- 

 ber held, upon a swelling of the external membrane. 

 Thus, in old cultures there is always a sort of agglutina- 

 tion, and then a dying out of the bacterial cells occurs. 

 The enzymes are usually only slightly specific; the pyocy- 

 aneum enzyme (pyocyanase) is, for example, active against 

 anthrax. They operate much better if oxygen is excluded 

 than in its presence. Also, certain bacterial poisons for 

 example, diphtheria toxins are destroyed by the pyocy- 

 aneum enzyme. 



