186 ORIENTAL PLAGUE chap. 



Experiment 4. — After a further week's (July 16) 

 withdrawal from sulphuric acid, the samples having been 

 kept meanwhile at the room temperature and in the air 

 of the laboratory, the same " sand-gelatine " and " earth- 

 gelatine" were used for injection of guinea-pigs Nos. 7 

 and 8 respectively. The " earth-gelatine " appeared now 

 as dry and hard as brick. The " sand-gelatine " guinea- 

 pig, No. 7, remained without swelling and quite well; 

 whereas the " earth - gelatine " guinea-pig, No. 8, de- 

 veloped a small firm nodule at the seat of inoculation. 

 This, however, almost entirely disappeared in the course 

 of a fortnight, the animal remaining lively and well. 



From these experiments it appears that gelatine 

 cultures mixed with sand and earth can be dried over 

 sulphuric acid for three days, until, for instance, the 

 material becomes distinctly hard and dry, without the 

 plague microbes losing their vitality ; and, further, it 

 appears that the " earth -gelatine" kept for additional 

 five days, till it had become as hard as brick, still retained 

 living and active B. pestis. 



Experiment 5. — In this experiment gelatine cultures 

 about six weeks old were (June 30) melted in warm 

 water and poured over wheat and rice in separate glass 

 dishes. After being well mixed in each instance the 

 materials were placed over sulphuric acid, of course in a 

 hermetically closed space. 



On July 1, i.e. after twenty -four hours, the materials 

 being now quite dry, a little of each sample was placed in 

 warm water and a guinea-pig was injected subcutaneously 

 with the emulsion thus obtained ; viz. guinea-pig No. 9, 

 with " rice-gelatine," and guinea-pig No. 10 with "wheat- 

 gelatine." Both animals developed big tumours in the 



