ANTITETANIC SERUM. 365 



potency of such poisons explains how, even in a fatal case, 

 extreme small ness of the wound and difficulty in isolating 

 the bacillus do not detract from the theory that the latter 

 is the cause of the disease. 



Immunity against Tetanus. Antitetanic Serum. 

 The artificial immunisation of animals against tetanus has 

 received much attention. The most complete study of the 

 question is found in the work of Behring and Kitasato in 

 Germany, and of Tizzoni and Cattani in "Italy. The former 

 observers found that such an immunity could be conferred 

 by the injection of very small and progressively increasing 

 doses of the tetanus toxine. The degree of immunity 

 attained, however, was not high. More successful was the 

 method of accompanying the early injections of such 

 toxine with the subcutaneous introduction of small doses 

 of iodine terchloride. Tizzoni and Cattani have also used 

 the method of administering progressively increasing doses 

 of living cultures attenuated in various ways, e.g., by heat 

 By any of these methods susceptible animals can rapidly 

 acquire great immunity, not only against many times the 

 fatal dose of tetanus toxine, but also against injections 

 of the living bacilli. The degree of immunisation acquired 

 by an animal remains in existence for several months. Not 

 only so, but the injection of the serum of such immune 

 animals can protect susceptible animals against the subse- 

 quent infection with a fatal dose of tetanus bacilli or toxine. 

 Further, if injected subsequently to such infection, the 

 serum can 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 infection with the bacilli or toxine and 

 the injection of the serum. The longer the interval which 

 is allowed to elapse, not only the greater must be the dose 

 of the serum but the less likely is cure to occur. In 

 animals, where symptoms have fully manifested themselves 

 only a small proportion of cases can be saved. As 

 in other cases, there is no evidence that the antitetanic 

 serum has any detrimental effect on the bacilli. It only 



