566 BACTERIOLOGY. 



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 bacterium diphtherice 

 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 1 ); 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 2 ). 3 

 TOXOIDS AND TOXONES. Ehrlich conceives the toxin 

 molecule to possess two atom-groups, a haptophore group, 

 by means of which it unites with certain cells of the body, 

 or with antitoxin ; and a toxophore group, by means of 

 which it produces its toxic effects. When preserved for a 

 time, or under the influence of various chemical and phys- 

 ical agents, the toxophore group of the toxin molecule de- 

 teriorates, so that it is no longer capable of exerting any 

 toxic action. The haptophore group is less easily dis- 

 turbed, and hence the combining power of the toxin 

 molecule may be unaltered, though it may have lost its 

 toxic properties. In this condition it is spoken of as 

 toxoid or toxone. A toxoid or toxone is still capable 

 of inducing antitoxin formation when injected into an 

 'animal, and it is also still capable of neutralizing anti- 

 toxin in the same proportions as before the alteration 

 had taken place. 



1 Annales de 1'Institut Pasteur, 1889, tome iii. p. 287. 



2 Zeitsehrift fur Hygiene und Infektionskrankheiten, 1893, Bd. xv. 

 Heft 1. 



3 By the use of more recently devised methods we are enahled to 

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

 the case with regard to the diphtheria toxin. 



