48 THE GROUSE DISEASE chap. 



In this disease, as in others, certain accessory or 

 secondary conditions are required in order to enable 

 the disease to assume the epidemic character. This 

 has been already mentioned ; and now we wish to 

 add that the microbe of the autumn disease seems 

 distinctly less virulent than that of the spring 

 disease. Inoculations of mice were made with recent 

 broth cultures derived from the heart's blood microbe 

 of autumnal cases, but in the majority of cases no 

 fatal result was produced, although all the animals be- 

 came ill. In a series of such experiments comprising 

 ten mice, all were quiet and off their food the day 

 after inoculation ; one died after three, one after seven 

 days, the other eight survived ; while of six mice 

 inoculated for control with recent broth culture of 

 the microbe of the lung of the spring disease, four 

 died in 48 hours, one during the third day, and only 

 one survived. 



Buntings and ammers so highly susceptible to 

 the spring microbe are also found less affected by 

 the autumn microbe ; most of them die, it is true, 

 but conspicuously at a later period than after inocu- 

 lation with the spring microbe ; they are ill for several 

 days, some die after the fourth, others after the fifth 

 day, their heart's blood containing the microbe in 

 large numbers. To prove that the autumn microbe 

 is of an attenuated virulence, I re-inoculated, after 



