Io6 MICRO-ORGANISMS AND DISEASE [chap. 



make their appearance in bacilli are spores ; thus in the 

 typhoid bacillus growing on potato, and in other species of 

 bacilli growing on potato, there appear bright granules, 

 either terminally or centrally, which are not spores ; they 

 do not show the reaction of spores, either to dyes, or on 

 drying, or heating. Nor are all the bright granules that 

 make their appearance in bacilli capable of forming spores 

 to be at once taken as spores, since under certain con- 

 ditions such granules do occur, but never reach the size of 

 full spores ; this is observed occasionally in anthrax bacilli 

 when growing under conditions unfavourable for the forma- 

 tion and development of spores. The appearance of real 

 spores in all bacillary species is very characteristic ; the spores 

 are of a bright, glistening aspect, are oval in shape, and gener- 

 ally thicker than the typical bacilli. The substance of these 

 latter is at the same time pale and transparent, and broader 

 than the bacilli not containing spores ; the threads of the 

 bacilli appear beaded by the spores, the beads being the 

 glistening oval thick spores, while the rest of the thread is 

 pale and appears thinner. In the single bacilli the spores 

 are placed either centrally or terminally ; in the latter case, 

 if the bacillus is of some length, it looks not unlike a 

 spermatozoon, the spore corresponding to the head, the 

 bacillus to the tail. Sometimes in motile bacilli short 

 chains are noticed, in which, in one terminal element, a 

 spore has already made its appearance, while the other 

 bacillus is still possessed of motility ; and here, on account 

 of the motility, the resemblance to a spermatozoon is still 

 more striking. Under the most favourable conditions 

 almost every element constituting a bacillary thread or 

 chain forms a spore, in other threads only here and there 

 a cell contains a spore ; in the first case the thread is 

 regularly and densely beaded, in the latter the beads are 



