DEVIATION 



27 



These various types in propagation or multiplication always 

 reproduce their own type, but it must be stated that under varying 

 conditions bacteria sometimes vary from their most typical shape. 

 For instance, the cause of pneumonia in man and animals is a double 



FIG. 4 



O 



5) 



b c d 



Types of bacteria (schematic): a, coccus; 6, bacillus; c, vibrio; d, spirillum. 



coccus, a so-called diplococcus, which in artificial cultures sometimes 

 becomes elongated, so that it is lancet-shaped instead of ball-shaped. 

 Other cocci may, under certain conditions, become flattened, so that 

 they look like a half-moon or somewhat like a crescent. Sometimes 

 bacilli in multiplying may become very short, so that they look on 



FIG. 5 



FIG. 



Very large spirilla. (Park.) 



Medium-sized spirilla. 



superficial examination like cocci. The three kinds named, however, 

 never change their shape permanently or so completely that they 

 really assume another type. 



Deviation (Pleomorphous Bacteria). Some bacteria, however, may 

 show, under certain conditions, not always well understood, certain 

 deviations from the common normal or average type. They may, for 



