40 BACTERIOLOGY. 



material, and are known as zooglcea of bacteria. (See 

 Fig. 6.) 



Very short oval bacilli may sometimes be mistaken 

 for micrococci, and at times micrococci in the stage of 

 segmentation into diplococci may be mistaken for short 

 bacilli ; but by careful inspection it will always be 

 possible to detect a continuous outline along the sides of 

 the former and a slight transverse indentation or par- 

 tition-formation between the segments of the latter. 

 The high index of refraction of spores, the property 



Fig. 6. 



;v.f..-«^" 

 •-'■■ - ■"'-v..';<;^v.---c!.'» 



Zooglcea of iDacilli. 



which gives to them their glistening appearance, will 

 always serve to distinguish them from micrococci. This 

 difference in refraction will be especially noticed if the 

 illumination from the reflector of the microscope with 

 which they are to be examined is reduced to the smallest 

 possible bundle of light-rays. The spores, moreover, 

 take up the staining reagents much less readily than 

 do the micrococci. The most reliable differential point, 

 however, is the property, possessed by the spores, of 

 developing into bacilli ; and of the spherical organism 

 with which it has been confounded, of producing other 

 micrococci of the same round form. 



For convenience, a common classification of the 

 bacilli is that based upon constant characteristics which 

 are seen to appear in the course of their development 



