SPORING BACILLI 315 



before symptoms arise. In the guinea-pig this is thirteen 

 to eighteen hours, and in the horse five days. It is shorter 

 after intravenous injection, probably through getting more 

 quickly to the nerve centres. Crocodiles are resistant to 

 tetanus toxin. 



Immunity. Produced by injection of filtered toxin 

 in increasing doses. At Elstree, the serum-producing 

 department of the Lister Institute, London, the horse is 

 immunized by the injection of 0-5 c.c. filtered toxin -f 0-5 

 c.c. of Lugol's solution of iodine (1-300), repeated at 

 intervals of ten days, gradually increasing the dose until 

 10 c.c. of unreduced toxin are given. The iodine solution 

 neutralizes the toxin to some extent. The serum of such 

 an immunized animal is antitoxic ; but the effect of its 

 injection into an infected animal is not so good as is the 

 case with diphtheria antitoxin, because the tetanus is 

 mainly bound to the nervous tissue and is thus less 

 susceptible to the action of the antitoxin. Von Behring 

 believes that there is no hope of its being useful after 

 symptoms have existed for 30 hours, but MacConkey and 

 Green say that if much larger doses were used better 

 results would be got in the human subject, comparable with 

 those reported in horses. The serum is standardized so 

 that 1 grm. will protect 100,000,000 grm. weight of mouse 

 (v. Behring), or 1,000,000,000 grm. weight (Pasteur 

 Institute). Of this 100 c.c. are advised to be injected 

 subcutaneously, and in the case of the first, repeated. The 

 argest dose that can be comfortably given at one spot is 

 20 c.c. Intravenous injection is said to give better results 

 than subcutaneous injection. The serum is warmed to 

 the body temperature and slowly introduced into an 

 arm vein, 10 to 20 c.c. every few hours. Intracerebral 

 injection has also been practised, but with no better 

 results. Prophylactic doses (10 c.c.) are advised as a 

 routine practice in ragged, bruised, and punctured wounds, 

 especially if soiled with material likely to contain tetanus 

 spores. The dose is given without unnecessary delay. 

 In U.S.A., in 1903, out of 4449 Fourth of July accidents, 

 406 were followed by death from tetanus, while in 1907, 

 only 62 tetanus deaths arose from 4413 accidents, and 

 much of the decrease is attributed to the early use of a 



