RESEARCHES ON CERTAIN PROBLEMS OF PLAGUE IMMUNITY 5 



resistant of the usual laboratory animals. The toxin is destroyed by a 

 temperature of 70° C. 



Lustig and Galeotti (1897) obtained toxic substances by extraction 

 with a one per cent, solution of caustic potash, and subsequent slight 

 over-neutralisation with a one-half per cent, acetic acid solution. The 

 resulting precipitate is highly toxic, and is employed as a vaccine. 



The German Plague Commission (1899) points out that certain 

 animal experiments indicate that the toxic action is not an important 

 feature of the pathogenic effects produced by the plague bacillus. They 

 refer to the condition observed in monkeys, in which a great part of the 

 body is affected with oedema, and where the exudate swarms with bacilli, 

 and yet in these animals strikingly few symptoms of toxaemia are 

 displayed. 



Notwithstanding this view of the Commission, it cannot be denied 

 that toxaemia is a marked feature in many cases of human plague. In 

 a considerable proportion of all cases the lesions remain localised in the 

 affected lymphatic glands, no bacilli being present in the blood-stream, 

 and yet these cases die with the symptoms of profound toxaemia. It is 

 certain that the pathogenic effects of the plague bacillus are the result of 

 toxic action. 



The English Plague Commission (1898-99), in speaking of the subject 

 of toxin, states, " We, for our part, have tested the effect which is exerted 

 by heat upon the filtrate from a plague culture. It results from these 

 experiments that the soluble toxins which are, under certain conditions, 

 developed in the fluid nutrient medium in which the plague bacilli are 

 grown, are apparently not affected by exposure to a temperature of even 

 100° C." 



The Austrian Plague Commission (Albrecht and Ghon, 1900), 

 obtained results in the main similar to Markl's, to be described directly. 

 Markl's work was done in part with the Commission. They obtained 

 toxic filtrates from broth cultures, the toxicity of which increased with 

 the age of the culture up to a certain period, two to three months, after 

 which no increase took place. The filtrates from cultures even only five 

 days old were toxic, and the toxins differed only quantitatively from 

 those obtained from older cultures. 



The bacillary bodies, from cultures on agar, which had been killed by 

 heating to a temperature of 55°-6o° C, produced toxic effects similar to 

 those observed with the filtrates. (115) I J 



