40 BACTERIOLOGY. 



Not infrequently bacteria may be observed irregu- 

 larly massed together as a pellicle. When in this condi- 

 tion they are held together by a gelatinous material, and 

 are known as zoogloea 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. G. 



Zooglcea of bacilli. 



which gives to them their glistening appearance, will 

 always serve to distinguish them from micrococci. This 

 difference in refraction is especially noticeable if the 

 illumination from the reflector of the microscope with 

 which they are examined be 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, how- 

 ever, is the property, possessed by the spores, of develop- 

 ing into bacilli; and by the spherical organism with 

 which it has been confounded, of producing other micro- 

 cocci of the same round form. 



For convenience, a common classification of the 



