

TETANUS TOXIN 273 



which has been carefully tested. The filtrate so obtained is free 

 from bacteria and spores, and contains the tetanus toxin in solution. 

 A good filtrate should contain a sufficient quantity of a strong toxin, 

 so that one two-hundred-thousandth part of a cubic centimeter will 

 kill a mouse of about 10 grams' body weight. Some investigators 

 have even, by special means, obtained a filtrate five times as 

 strong, of which the one-millionth part of a cubic centimeter would 

 kill a mouse of about 10 grams' body weight. By saturating the 

 filtrate with ammonium sulphate, Brieger, Frankel, Buchner, and 

 others succeeded in precipitating the toxin in the form of a powder, 

 of which the one ten-millionth part of a gram would kill a mouse of 

 10 grams' body weight. Other animals, however, are more suscep- 

 tible than the mouse to the fatal action of tetanus poison; the horse, 

 for example, is twelve times as susceptible, and on the basis of 

 the above figures a horse weighing 2000 pounds can be killed by 

 one twelve-hundreth gram, or about one-eightieth of a grain of 

 dried tetanus poison. Such powerfully poisonous effects are almost 

 inconceivable. The tetanus toxin is even more powerful than the 

 venom of the most dangerous snakes, such as the cobra. Man also is 

 more susceptible than the mouse, but probably less than the horse, 

 which is the most susceptible animal. The exact susceptibility of man 

 as compared with the mouse and the horse is not known, since it 

 cannot, of course, be ascertained by experimental work. The guinea- 

 pig is 6 times as susceptible as the mouse; all other animals tested 

 are less susceptible than the mouse; the rabbit 150 times less sus- 

 ceptible, the goose 1000 times, the pigeon 4000 times, and the chicken 

 30,000 times. The latter figure indicates that for each gram or 

 pound of body weight of chicken 360,000 times as much tetanus 

 toxin is needed as for each gram or pound of body weight of a 

 horse in order to produce the same fatal effect. 



Period of Incubation of the Toxin. Bacteria and their toxins never 

 act like purely chemical poisons, such as acids, alkalies, or salts 

 (strychnine or hydrocyanic acid and its salts, cyanide of potash). 

 Such poisons may be given in doses large enough to produce death 

 almost instantly. However, if the most pathogenic bacteria or their 

 toxins are inoculated into an animal even in very large doses, death 

 never takes place immediately; a certain period of time always elapses 

 between the inoculation and the first symptoms. When tetanus toxin is 

 inoculated into a mouse or guinea-pig the period of incubation becomes 

 shorter as the dose is increased; but it is impossible to go beyond a 

 certain minimum period of incubation, no matter how much the 

 toxic dose is increased. If mice receive 3600 times the fatal dose of 

 tetanus toxin the period of incubation is shortened to a minimum 

 of eight hours. 



Chemistry of the Toxin. Instability. The chemistry of the 

 tetanus toxin is absolutely unknown, and it can only be identified 

 by its effect upon experimental animals; but it can, of course, also 

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