GENERAL MORPHOLOGY 25 



than the others, extending from a simple comma shape 

 to that of a long wavy spiral when looked at from the 

 side. These last are in reality corkscrews, as they twist 

 in three planes. In size microorganisms vary consider- 

 ably. Perhaps a proper conception of some organisms 



FIG. 3 



-^ 



<^>w V 



a, bacilli in pairs; b, single bacilli; c and d, bacilli in threads; e and /, 

 bacilli of variable morphology. (Abbott.) 



FIG. 4 



o b c d 



a and d, spirilla in short segments and longer threads the so-called 

 comma forms and spirals; b, the forms known as spirochsetse, c, the thick 

 spirals sometimes known as vibrios. (Abbott.) 



can be obtained when one considers that to cover one 

 square inch in single layer it would require 6,250,000,000 

 influenza bacilli, a very small organism, or 45,000,000 

 anthrax bacilli, a bacterium of moderate size. Bac- 

 teria are measured in terms of microns. The metric 

 unit, a micron, equals about 2TTro^r f an inch. 



