384 
LEONARD PEARSON. 
purating wound at the point of inoculation and more or less con¬ 
gestion of the central nervous system. 
It has been shown by experiments conducted by Behring 
and Kitasato that the trichloride of iodine restricts to a very 
great extent the vitality and virulence of the tetanus bacillus, 
and by introducing into susceptible animals small quantities of 
tetanus cultures that have been treated with this agent, and 
gradually increasing the strength of such cultures by using 
smaller quantities of the trichloride of iodine, a certain degree 
of immunity can in time be developed, so that at last very large 
quantities of pure culture can be introduced without producing 
tetanus. An animal treated in this way gradually develops in 
its blood a chemical substance that neutralizes the effect of the 
toxin of tetanus, and which is, therefore, known as an anti¬ 
toxin. 
The immunity that the animal possesses depends upon the 
antitoxin that is present in its blood. If another susceptible 
animal is inoculated with a fatal dose of tetanus toxin, and is 
treated immediately thereafter with an adequate amount of an¬ 
titoxin derived from the serum of the immunized animal, the 
development of the disease will in this way be prevented, and it 
is upon this principle that the treatment of tetanus with anti¬ 
toxin is based. Experiments conducted by Vaillard and Rouget 
have shown, that if the toxin is removed from the tetanus ba¬ 
cilli, they can then be introduced into an experimental animal 
without evil effects, because they are quickly taken up by phag¬ 
ocytes and destroyed; but when tetanus bacilli containing 
antitoxin are introduced they are not taken up by phagocytes, 
and quickly produce toxin, causing the development of tetanus. 
The antitoxin, injected immediately after the toxin-containing 
bacilli are introduced into the body, neutralizes their poison to 
such an extent that they can be destroyed by the phagocytes ; 
but if the antitoxin is not present in the blood ^^en the animal 
is inoculated with the germs of tetanus, or if it is not introdnced 
into the circulation shortly thereafter, the tetanus bacilli pro¬ 
duce so much toxin that it cannot be neutralized, and the de- 
