540 BA CTEBIOL G Y. 



group comprises diiferent bodies of the nature of globu- 

 lins, nucleo-albuinins, peptones, albumoses, and enzymes 

 or ferments. 



Toxic ptomains are probably not conspicuously con- 

 cerned in producing the characteristic symptoms of 

 infection, as they are absent from cultures of certain 

 highly pathogenic bacteria. 



In particular instances the production of poisonous 

 principles, even under artificial conditions of cultivation, 

 is most astonishing, and poisons are generated that in the 

 degree of their toxicity exceed anything hitherto known 

 to us. For instance, the potencies of the poisons that 

 have been isolated from cultures of baeillus diphtheriw 

 and of bacillus tetani have been carefully determined 

 by experiments upon animals, and it has been found 

 that 0.4 milligramme of the former is capable of 

 killing eight guinea-pigs, each weighing 400 grammes, 

 or two rabbits, each weighing 3 kilogrammes (Roux and 

 Yersin ') ; and that 0.0001 milligramme of the latter 

 will produce tetanus in a mouse, with all the character- 

 istic manifestations of the disease (Brieger and Cohn ^).* 



Briefly stated, the invasion of the body by infective 

 micro-organisms may best be conceived as a contest 

 between the invading organisms on the one side and 

 the resisting tissues of the animal body on the other ; 

 the weapons of offence of the former being the poison- 

 ous products of their growth, while the means of 

 defence possessed by the latter are vital substances 



' Annales de I'lnstitut Pasteur, 1889, tome iii. p. 287. 



2 Zeitsclirift fiir Hygiene unci Infektionskrankheiten, 1893, Bd. xv. 

 Heft 1. 



' By tie use of more recently devised methods we are enabled to 

 increase still further the toxicity of these poisons; especially is this 

 the case with regard to the diphtheria toxin. 



