BACTERIA IN DIPHTHERIA. 379 



cultures were found by these experimenters to contain more of the 

 toxic substance than recent ones, and to cause the death of a guinea- 

 pig in the dose of two cubic centimetres in less than twenty-four 

 hours. The filtered cultures produced in these animals the same 

 effects as those containing the bacilli local oedema, hsemorrhagic 

 congestion of the organs, effusion into the pleural cavity. Some- 

 what larger doses were fatal to rabbits, and a few drops injected 

 subcutaneously sufficed to kill a small bird within a few hours. In 

 their second paper (1889) the authors mentioned state that so long as 

 the reaction of a culture in bouillon is acid its toxic power is com- 

 paratively slight, but that in old cultures the reaction is alkaline, 

 and in these the toxic potency is greatly augmented. With such a 

 culture, filtered after having been kept for thirty days, a dose of 

 one-eighth of a cubic centimetre, injected subcutaneously, sufficed 

 to kill a guinea-pig ; and in larger amounts it proved to be fatal 

 to dogs when injected directly into the circulation through a vein. 



The same authors, in discussing the nature of the poison in their 

 filtered cultures, infer that it is related to the diastases, and state 

 that its toxic potency is very much reduced by exposure to a com- 

 paratively low temperature 58 C. for two hours and completely 

 destroyed by the boiling temperature 100 for twenty minutes. It 

 was found to be insoluble in alcohol, arid the precipitate obtained by 

 adding alcohol to an old culture proved to contain the toxic sub- 

 stance. Loffler also has obtained, by adding five volumes of alco- 

 hol to one of a pure culture, a white precipitate, soluble in water, 

 which killed rabbits in the dose of 0. 1 to 0. 2 gramme when injected 

 beneath the skin of these animals. It gave rise to a local oedema 

 and necrosis of the skin in the vicinity of the point of inoculation, 

 and to hypersemia of the internal organs. This deadly toxin appears 

 to be an albuminoid substance, but its exact chemical composition 

 has not yet been determined. * 



Brieger and Frankel have succeeded in rendering guinea-pigs 

 immune against virulent cultures of the diphtheria bacillus by inject- 

 ing bouillon cultures three weeks old, which had been sterilized by 

 exposure for an hour to 60 to 70 C., into the subcutaneous tissues 

 (ten to twenty cubic centimetres). At first the susceptibility of the 

 animal is rather increased than diminished, but at the end of two 

 weeks immunity is said to be complete. Frankel is of the opinion 

 that immunity results from the introduction of a substance which is 

 not identical with the toxic product to which the cultures owe their 

 pathogenic power. This latter is destroyed by a temperature of 55 

 to 60 C., while the substance which gives immunity is still present 

 in the cultures after exposure to a temperature of 60 to 70, as shown 

 by the protective results of inoculations made with such cultures. 



