DII'HTHEROID ORGANISMS. 77 



attaches importance to the dots at both ends as showing 

 diphtheria. 



2. They tend to stain solidly or at most with only a single 

 unstained segment. They are shorter, thicker and do not 

 curve so gracefully as the true diphtheria bacillus. They 

 are stockier. 



3. They produce very little acid in sugar media, not one-half 

 that produced by true diphtheria. 



4. They are nonpathogenic for guinea-pigs. 



5. Many of them grow quite luxuriantly and often show 

 chromogenic power. 



Xerosis Bacillus. This organism is frequently found in normal 

 conjunctival discharges. There is question as to its pathogenesis, and 

 the finding of this organism should not exclude the previous presence of 

 strictly pathogenic organisms, such as the gonococcus or the Koch- 

 Weeks. It resembles the diphtheria bacillus in being Gram positive 

 and showing parallelism, but differs (i) in being nonvirulent for 

 guinea-pigs; (2) in requiring about two days for the appearance of 

 colonies; (3) in not showing Neisser's granule staining, and (4) in 

 producing very little acid in sugar media. 



