104 MICRO-ORGANISMS AND DISEASE. [CHAP. 



the bottom of the fluid layer, is thus removed from the surface. 

 The spores which were freely formed while the growth went 

 on on the surface, germinate again into bacilli, but because 

 these have now sunk into the depth, although rapidly 

 multiplying and growing into filaments, they cease to form 

 any spores. 1 



Bacilli which are not possessed of the power of locomotion 

 (i.e. are without a flagellum) when sown into the depth of a 

 fluid or solid material, if they have no chance, accidental or 

 otherwise, of reaching the surface, do not as a rule form 

 spores; but there are some such bacilli which, although 

 not growing on a free surface, nevertheless form spores, 

 e.g. the bacillus butyricus or amylobacter (Prazmowski). 

 Some putrefactive bacilli occurring after death in the 

 abdominal organs (intestine, kidney, spleen, liver), and 

 in fluid exudations within the peritoneal and pleural 

 cavities, show also spore-formation ; probably they get 

 their oxygen from the tissues. Anthrax-bacillus, however, 

 never forms spores except it is growing well exposed to the 

 outer air. 



The bacilli which are possessed of a flagellum (e.g. hay- 

 bacillus, bacillus of putrefaction) generally form a pellicle 

 on the surface, and in this pellicle copious spore-formation 

 goes on. 



The spores first formed, when shaken down into the 

 fluid, again germinate into bacilli, and there multiply. 

 The last pellicle formed in a culture, before exhaustion, 

 represents the last crop of spores ; and these, owing to the 

 exhaustion of the nourishing fluid, remain as spores, only 

 capable of germinating into bacilli when new nourishing 

 material is added, or when they are transplanted to new 

 nourishing material. 



1 Report of the Medical Officer of the Local Government Board, 1881. 



