BACTERIOLOGICAL INTRODUCTION 21 



as the resistant cells which occur in nearly every 

 culture. 



The formation of the Endospores is much better 

 known, and occurs in certain of the bacilli and 

 spirilla. Bacilli with endospores are shown in Fig. 

 11 and in several other photographs (17, 94, and 97) 

 illustrating special organisms. The spore appears 

 as a refracting granule within the cell in the position 

 subsequently occupied by the developed spore, or as 

 a number of scattered granules which coalesce to 

 form the spore. In any case, as development pro- 

 ceeds, the granule grows and becomes an oval or 

 spherical thick-walled, highly refractile body, while 

 at the same time, as a rule, the protoplasm of the 

 cell grows more and more translucent, and appears 

 to be absorbed in the formation of the spore. The 

 spores may, in relation to the mother cells, be 

 central or polar. In Fig. 12 and in Fig. 17 they are 

 centra] and do not deform the cell, the short axis of 

 the spore being less than the diameter of the cell. 

 In Fig. 97 they are central, and in Fig. 94 they 

 are polar, but in both cases cause by their size a 

 modification in the mother cell, causing it in the 

 first case to become fusiform, and in the second to 

 assume a drumstick character. These modified 

 spore-bearing cells are known as clostridia. One 



