<;!:. \ERAL CHARACTERISTICS OF BACTERIA 



27 



they generate rod-like forms. These apparently spherical bacteria we can 

 properly regard as short forms of bacilli, which, owing to the rapidity of 

 division, are for the time being of the same size in both diameters. Under 

 suitable conditions, however, the true rod-shape is always developed. 



FIG. 3 



W*f 



Various forms of bacilli : a, bacilli with sides parallel to their Ion? axis and with ends perpen- 

 dicular ; 6, bacilli with sides swollen or narrowed, causing irregular forms. (Alter FlUgge.) 



2. ROD FORM, OR BACILLUS. The type of this group is the cylinder. 

 The length of the fully developed cell is always longer than its breadth. 

 The size of the cells of different varieties varies enormously, from a length 

 of 30u and a breadth of 4u to a length of 0.2, and a breadth of O.I/*. 

 The largest bacilli met with in disease do not, however, average over 

 3. In describing their forms bacilli are roughly classed as slender 



FIG. 4 



FIG. 5 



Medium bacilli, single and in pairs. 



Small bacilli, mostly in pairs. 



when the ratio of the long to the transverse diameter is from 1 : 4 to 

 1 : 10, and as thick when the proportions of the long to the short diameter 

 is approximately 1 : 2. 



The characteristic form of the bacillus is one with a straight axis, 

 uniform thickness throughout, and flat ends (Fig. 3 a, and Fig. 6); but 



