52 THE GROUSE DISEASE chap. 



conditions — those that form spores, and as spores, 

 resist all the above influences. In the case of 

 pathogenic bacteria those that form spores, e.g. the 

 bacillus antkracis, the bacillus of the classical malig- 

 nant oedema, the tetanus bacillus, — having formed 

 spores, as spores are, for the above reasons, of 

 the utmost importance in etiological respects ; for 

 the spores, even when finding themselves under very 

 unfavourable conditions, retain their vitality, and, 

 having access to a suitable animal body, are capable 

 of setting up the disease. In the case of non-spore- 

 bearing forms this can only happen if they are for- 

 tunate enough to be shielded in one way or another 

 from these obnoxious influences. 



Now the bacillus of grouse disease belongs to the 

 group of pathogenic organisms which do not form 

 spores. On microscopical examination of fresh and 

 of stained specimens there is no indication of the 

 presence of anything that will compare with the 

 spores in those species of bacilli in which spores do 

 occur, and the experiments on the influence of heat 

 and of drying fully bear this out. A culture of the 

 grouse bacillus exposed to a temperature of 60° C. for 

 five minutes becomes hereby completely sterilised ; 

 no new sub-culture can be produced from it. Or, if 

 a culture medium in a test-tube or flask is inoculated 

 with the living grouse bacilli, then exposed to 60° C. for 



