130 



BACTERIOLOGY. 



and at certain points in the thread a speck ap- 

 pears, which gradually enlarges and develops into 

 a circular or egg-shaped, sharply defined, highly 

 refractive body. The spore grows at the expense 

 of the protoplasm of the cell, which in time, to- 

 gether with the cell-wall, entirely disappears, and 

 the spore is set free. These phenomena are best 

 seen in an immotile bacillus, in a drop-cultivation 



FIG. 53. CLOSTRIDIUM BUTYRICUM, x 1020. 



B. Stages of spore-formation. 



C. Stages of germination. 



[After Prazmowski.] 



on a warm stage, the whole process may then 

 be observed continuously from beginning to end. 

 Spores may form in each link of the thread, so 

 that a regular row results, or they may occur at 

 irregular intervals. Spore-formation also occurs in 

 free rods in the centre or at one end. Occasionally 

 a spore develops at the extreme end, giving a bacillus 

 the appearance of a drum-stick. The spore may be 



