156 



THE AMERICAN MONTHLY 



[May 



call them staphylococci ; an example of these is furnished 

 by the ordinary pns-germs. When in groups of two, 

 they are termed diplococci (Fig 2); perhaps the most im- 

 portant illustration of this class is the germ of pneu- 

 monia. When occurring in chains or threads containing 

 many cells, the name streptococcus (Fig. 3) is given ; as 

 the streptococcus of erysipelas or tonsilitis. Then again, 

 from division in three directions, we may gel little square 



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packages of germs: these are called sarcines (Fig. 4); 

 many of our harmless water bacteria form groups in this 

 way. The second class, called bacilli (the word bac- 

 illus means ''a small rod" — see Fig. 5), may occur in 

 dense masses or singly, as with the tubercle bacilli, ty- 

 phoid fever and many of the other common pathogenic bac- 

 teria. Again, they may form long threads, as is noticed 

 with anthrax germs, which, until Pasteur's discoveries a 

 few years ago, threatened to annihilate all the herds of 

 Europe. Bacilli may be short or long, thick or slender,, 



