366 TETANUS. 



neutralises the effects of the toxine. The standardisation 

 of the antitetanic serum is of the highest importance. 

 Behring recommends that for protecting animals a serum 

 should be obtained of which one gram will protect 1,000,000 

 grams weight of mice against the minimum fatal dose of the 

 bacillus or toxine. A mouse weighing twenty grams would 

 thus require .00002 grams of such a serum to protect it 

 against the minimum lethal dose. In the injection of such 

 a serum subsequent to infection, if symptoms have begun 

 to appear, 1000 times this dose would be necessary ; a few- 

 hours later 10,000 times, and so on. 



As the result of his experiments, Behring aimed at obtain- 

 ing a curative effect in the natural disease occurring in man. 

 For this purpose, as for his later laboratory experiments, 

 he obtained serum by the immunisation of such large 

 animals as the horse, the sheep, and the goat. The prin- 

 ciples of the process were the same as in his earlier work, 

 namely, the injection of toxine, accompanied at first with 

 the injection of iodine terchloride. It was found that 

 the greater the degree of the natural susceptibility of an 

 animal to tetanus, the easier was it to obtain a serum of a 

 high antitetanic potency. The horse was, therefore, the 

 most suitable animal. If now we take for granted that the 

 relative susceptibility of man and the mouse towards tetanus 

 are nearly equal, a man weighing 100 kilograms would 

 require . i gram of the serum mentioned above, to protect 

 him from inoculation with the minimum lethal dose of 

 bacilli or toxine. If symptoms had begun to appear, 100 

 c.c. at once would be necessary, and as the injection of 

 such a quantity might be inconvenient, Behring recom- 

 mended that for man a more powerful serum should be 

 obtained, viz. a serum of which one gram would protect 

 100,000,000 grams weight of mice. 1 Here, as in all anti- 

 tetanic sera, the potency is maintained for several months 

 if precautions are taken to avoid putrefaction. To this end 



1 The antitetanic serum sent out by the Pasteur Institute in Paris has 

 a strength of i : 1,000,000,000. Of this it is recommended that 50 to 

 100 c.c. should be injected in one or two doses. 



