1917] Studies on Coccobacillus Acridiorum D'Herelle 57 



as sharply defined and compact as they appear in a more con- 

 centrated agar. The typical colonies appeared within ten 

 hours and the culture was always ready for use within 18 hours. 



An attempt was made to estimate the number of viable 

 organisms found in the digestive tract of insects which had died 

 from the disease and also of those which survived infection. 

 As one would expect, the number of coccobacilli in the intestines 

 of dead locusts varied between very wide limits, depending 

 probably on the length of time elapsing between infection and 

 death, and on the number of organisms originally injected. 

 The number usually exceeded 100,000 and our experiments 

 showed that this number continued to increase after the death 

 of the host. 



4 hours after inoculation, just dead, 100,000 organisms. 



10 hours after inoculation, 6 hours dead, 400,000 organisms. 



24 hours after inoculation, 20 hrs. dead, 5,000,000 organisms. 



Locusts which survived infection gave a much lower count, 

 as the following table shows: 



TABLE VI. 



NUMBER OF COCCOBACILLI IN INTESTINAL TRACT OF LOCUSTS SURVIVING INFECTION. 



Viability of Coccobacillus acridiorum i?i Bran Mash. 



If bran mash is used for the conveyance of the coccobacillus 

 it would be important to know how long the organism will retain 

 its virulence in the mash. To test this we placed a shallow 

 receptacle of bran in the shade out of doors. On the first day 

 there were 365 million coccobacilli per gram of bran mash. 

 After four days the numb.er was reduced to 100 million, and a 

 few of the locusts which were fed this mash died. At the end of 

 eight days there were 250,000 coccobacilli per gram of bran 

 mash. Locusts injected with a pure culture of coccobacilli 

 from the eight day old bran did not die. 



