282 BACTERIOLOGY. 



tures it will be found on microscopic examination to 

 present an arrangement somewhat like a chain of beads. 

 (Fig. 560 



Determine its peculiarities and describe them accu- 

 rately. They should be as follows : 



Upon microscopic examination a micrococcus should 

 be found, but differing in its arrangement from the 

 staphylococci just described. The single cells are not 

 scattered irregularly or arranged in clumps similar to 

 bunches of grapes, but are joined together in chains like 

 strands of beads. These strands are sometimes regular 

 in the arrangement and size of the individual cells com- 



FIG. 56. 



Streptococcus pyogenes. 



posing them, but more commonly certain irregular groups 

 may be seen in them. Here they appear as if two or 

 three cells had fused together to form a link, so to speak, 

 in the chain, that is somewhat longer than the remaining 

 links ; again, portions of the chain may be thinner than the 

 rest, or it may appear broken or ragged. Commonly the 

 individuals comprising this chain of cocci are not round, 

 but appear flattened on the sides adjacent to one another. 

 The chains are sometimes short, consisting of four to six 

 cells ; or, again, they may be much longer, and extend from 

 a half to two-thirds across the field of the microscope. 



Under artificial conditions it sometimes grows well, 

 and can be cultivated through many generations, while 



