21 
The filtrate placed in the window in diffuse light gradually lost its 
properties. It lasted, however, a long time before it was entirely 
destroyed. After it had been nine or ten weeks at the window it 
was still toxic, but in large doses. The filtrate kept cold in a dark 
room retained its toxic properties much longer, for after three hundred 
da^^s it was still equally as toxic as when fresh. 
Direct sunlight totally destroys the tetanus poison in from fifteen 
to eighteen hours. 
Diluting the poison with water or bouillon does not seem to harm 
it in any way. 
Hydrochloric acid influences the tetanus poison when added in the 
proportion of 0.55 per cent within one hour, and in the amount of 
0.1365 per cent within twenty-four hours completely destroys the 
poison. 
From similar experiments with many chemical substances Kitasato 
drew the conclusion that the tetanus poison is very susceptible to 
acids, especially mineral acids, as well as alkalies. 
Tizzoni and Cattani,^ 1891, have shown that silver nitrate, subli- 
mate, and hydriodic acid alter the toxicity of filtered tetanus cultures; 
carbolic acid, chlorine water, and iodidum trichloride were also found 
to have the same effect. Tizzoni and Cattani had much difficulty at 
first in immunizing animals with large doses of the tetanus toxine in 
order to obtain potent antitoxin. On account of the virulence of the 
poison many animals were sacrificed. They found that treating the 
toxine with iodine trichloride was useful in order to weaken the poison, 
and thus permit the use of large doses, which could then be rapidly 
increased. 
Vaillard and Vincent,^ 1891, showed that the tetanus toxine is 
modified or destroyed by temperatures exceeding 65° C. It is con- 
siderably attenuated when heated in a vlosed flask for forty minutes 
at 60° C. or twenty minutes at 62° C. Heating for thirty minutes at 
65° C. in closed flasks renders it inactive. Kept in a closed flask free 
from air and light the liquid toxine keeps its activity for a long time ; 
after four months there is no change in its toxicity. Exposed to the 
air in a thin layer it loses its activity after a month; this action is more 
rapid and greater in sunlight. 
Acidification of the liquid by tartaric acid does hot modify its 
toxicity. It can be dried in a vacuum over H 2 SO 4 and is extremely 
toxic. 
« Tizzoni, G., and Cattani, Giuseppina: Ueber die Eigenscliaften des Tetanus- 
Antitoxins. Centblt. f. Bakt., Ref., vol. 9, 1891, pp. 189, 685. 
^Vaillard, L., & ATncent, H.; Contribution a I’etude du tetanos. Ann. Inst. 
Pasteur, vol. 5, 1891, p. 1. 
