434 TETANUS 



tion procedures. In fact it is doubtful if small animals can be 

 immunised at all by fresh filtrates. ) In some cases the injection 

 of non-lethal doses instead of commencing an immunity actually 

 increases the susceptibility of the animal, and this may be related 

 to the development of supersehsitiveness to proteids generally 

 (see " Anaphylaxis " under Immunity). (^More successful in 

 producing immunity are the methods of accompanying the early 

 injections of crude toxin with the subcutaneous introduction of 

 small doses of iodine terchloride, or of using toxin which has 

 been acted on with iodine terchloride or with iodine itself. 

 Living cultures attenuated in various ways, e.g., by heat, have 

 also been used. By any of these methods susceptible animals 

 can be made to acquire great immunity against large doses of 

 tetanus toxin, and also against living bacilli. Immunity thus 

 acquired remains in existence for a very long time. The serum 

 of such immune ' animals possesses the capacity of protecting 

 animals susceptible to the disease against a subsequent injection 

 of a fatal dose of tetanus bacilli or toxin. Further, if injected 

 subsequently to infection, the serum can in certain cases 

 prevent a fatal result, even when symptoms have begun to 

 appear. The degree of success* attained depends, however, on 

 the shortness of the time which has elapsed between the injection 

 of the bacilli or of toxin and the injection of the serum. In 

 animals where symptoms have fully manifested themselves only 

 a small proportion of cases can be saved. As with other anti- 

 toxins, there is no evidence that the antitetanic serum has any 

 detrimental effect on the bacilli. It only neutralises the effects 

 of the toxin. The standardisation of the antitetanic serum is of 

 the highest importance. Behring recommended that for protecting 

 animals a serum should be obtained of which one gramme will 

 protect 1,000,000 grms. weight of mice against the minimum 

 fatal dose of the bacillus or toxin. A mouse weighing twenty 

 grms. would thus require '00002 grm. of the 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. 



The Therapeutic Application of Tetanus Antitoxin. — As 

 the results of his experiments, Behring aimed at obtaining a 

 curative effect in the natural disease occurring in man. For 

 this purpose he immunised large animals such as the horse, the 

 sheep, and the goat. It is found that the greater the degree of 

 the natural susceptibility of an animal to tetanus, the easier is it 

 to obtain a serum of a high antitetanic potency. The horse is, 



