Xlii] MICROBES OF MALIGNANT ANTHRAX 285 



access of air, or on solid media (e.g. serum gelatine, gelatine 

 broth, Agar-Agar, potato, &c.), the bacilli, having developed 

 into filaments, proceed to form spores. But they may form 

 spores even in fluid media if by some accident, either by 

 sticking to the glass vessel containing the fluid or by means 

 of a cotton-wool fibre, some of the bacilH remain on the 

 surface of the fluid. This formation of spores is not due to 

 exhaustion of the nourishing medium, as has been already 

 discussed on a former page, but represents the last stage in 

 the life-history of the bacilli, provided they have an ample 

 supply of oxygen. If this latter condition is not fulfilled, 

 as when they are grown at the bottom of a fluid, the bacilli 

 gradually degenerate as mentioned above. 



Spore-formation occurs, cmteris paribus, at all tempera- 

 tures between 18° and 45" C. Koch found 15" C. the 

 lower limit. Under the most favourable conditions, each 

 cubical or rod-shaped mass of protoplasm includes one 

 spore, in which case the bacillar filament contains an almost 

 unbroken row of spores ; but in other cases only an elemen- 

 tary mass here and there contains a spore, the rest breaking 

 down and becoming absorbed. In the first case, also, the 

 protoplasm of the elements almost entirely disappears, the 

 sheath swelling up and becoming hyaline, and only the 

 bright spores remaining. Their linear arrangement, however, 

 still indicates that they were formerly contained in one 

 filament. 



If bacilli grow in the depth of a fluid medium, they do 

 not form spores, as has been stated above ; and, as we have 

 also seen, as new bacilli appear, or the old filaments increase 

 in length, degeneration sets in. This degeneration gradually 

 affects greater and greater numbers, and when the fluid is 

 exhausted for the formation of new bacilli it necessarily 

 follows that the whole growth gradually becomes involved in 



