396 BACTERIOLOGY. 



to the septicsemic class of organisms which spreads 

 through the body, and by their growth and increase 

 produce their effects, but, on the contrary, remains 

 localized at the original point of infection. It pro- 

 duces, however, in its growth a most powerful toxin. 

 The treatment of tetanus is, therefore, directed against 

 the production of toxin and its neutralization in the 

 body. The methods originally proposed by Behring and 

 by Roux for producing a curative serum consisted 

 chiefly in weakening the tetanus toxin by means of 

 chemical, disinfectants (iodine trichloride, Gram's and 

 LugoPs solutions), so that when inoculated into the 

 test-animals they produced comparatively little reac- 

 tion. At the present time we inject the pure unaltered 

 toxin either alone in small doses or along with anti- 

 toxin. After the first dose of toxin the animals acquire 

 a certain tolerance which enables them to stand a dose 

 of a less attenuated toxin or of a greater amount of un- 

 changed toxin. Thus by gradually increasing the doses 

 or the strength of the toxin administered, the animals 

 are finally able to bear injections of large quantities of 

 the strongest toxin. 



These immunizing experiments in tetanus have borne 

 practical fruit, for it was through them that the prin- 

 ciple of serum-therapeutics first became known the 

 protective and curative effects of the blood -serum of 

 immunized animals. It was thus shown that animals 

 could be protected from tetanus infection by the pre- 

 vious or simultaneous injection of tetanus antitoxin, 

 provided that such antitoxic serum was obtained from 

 a thoroughly immunized animal; and from this it was 

 assumed that the same result could be produced in natu- 

 ral tetanus in man; but, unfortunately, the conditions 



