392 BACTERIOLOGY. 



in diphtheria. It may well be supposed that the mucous 

 membranes of the bronchi, and other similar mem- 

 branes, in a condition of catarrhal inflammation, may 

 be more susceptible to tetanus infection than they 

 normally are. 



Tetanus Toxin. It is evident from the localization of 

 the tetanus bacilli at the point of inoculation and their 

 slight multiplication at this point that they owe their 

 action to the production of a powerful toxin. While 

 there are a few cases on record in which the bacilli 

 have been found in the tissues of the animal body 

 other than the point of infection, the fact remains that 

 in the vast majority of cases the tetanus bacillus is 

 localized. This toxin can be readily separated from 

 cultures by filtration. One-hundredth of a milligramme 

 of an eight-day filtered bouillon culture is sufficient, as 

 a rule, to kill a mouse. From this filtrate, however, 

 the active toxic substance has been obtained in a much 

 more concentrated form. The purified and dried tetanus 

 toxin prepared by Brieger and Cohn was surely fatal to 

 a 15 gramme mouse in a dose of 0.00000005 gramme. 

 Reckoning according to the body-weight of 75 kilo- 

 grammes, or 175 pounds, it would require but 0.00023 

 gramme, or 0.23 milligramme of this toxin, to prove 

 fatal to a man. By comparing this with snake- 

 poison, Calmette has found that dried cobra venom 

 requires 0.25 milligramme to kill a rabbit of 4 kilo- 

 grammes' weight, and according to body-weight, it 

 would require 4.375 milligrammes to kill a man of 70 

 kilogrammes. As the fatal dose of atropine for an 

 adult is 130 milligrammes, of strychnine from 30 to 

 100 milligrammes, and of anhydrous prussic acid 54 

 milligrammes, the appalling strength of the tetanus toxin 



