LIFE OF ELIE METCHNIKOFF 211 



and in virulence. He had described this phenomenon 

 in 1888 in a memoir entitled PleomorpJiism of 

 Microbes. His hypothesis would explain the liability 

 of the Kabnuks, since, if no tuberculous bacilli 

 existed in the steppes, the inhabitants could not 

 acquire a natural vaccination. When placed in an 

 environment which was not free from tuberculosis, 

 they became infected very easily, being in no wise 

 prepared for the struggle against the virus. 



The expedition to the Kalmuk country was there- 

 fore planned in order to ascertain whether tuber- 

 culosis was really absent from the steppes. This could 

 easUy be done by Pirquet's test,^ which at the same 

 time would show whether the number of Kalmuks 

 infected increased from the centre to the outer limit 

 of the steppes and corresponded with the greater 

 degree of contact with the surrounding population. 

 If the enquiry confirmed the hypothesis, there would 

 remain to be seen which microbes might best be used 

 as vaccines. 



The expedition was also intended to elucidate ^ 

 few questions on the etiology of endemic plague in 

 the Kirghiz steppes. When this intention became 

 known, the Russian authorities desired to add to it 

 a local mission on the study of plague epidemics in 

 the steppes. MetchnikofE, who was chiefly concerned 

 with the question of tuberculosis, was only able to 

 draw up a plan of work for the Russian mission and 

 to start it going in one of the plague centres. 



The Pasteur Institute expeditionary party com- 

 prised, besides MetchnikofE, MM. Burnet, Salimbeni, 

 and lamanouchi. They were joined at Moscow by 



^ A cutaneous soarifioation by tuberculin which provokes local inflam- 

 matory redness on the scarified point in tuberculous subjects only. 



