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 
norwally 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 
lovalized.. 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 Cobn 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 
requ.res 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 
