CORYNEBACTERIUM DIPHTHERIA. 403 



4. Virulent D. B. , typical in every way, but with very 

 little tendency to the formation of longer forms. 



5. Virulent D. B. , typical in every way, but with such 

 luxuriant growths upon glycerin-agar and potato that they 

 cannot be distinguished macroscopically from the Coryne- 

 bacterium pseudodiphtheriticum. 



In other words, we speak of a true diphtheria bacillus 

 'whenever a bacillus stains in segments and presents a dis- 

 tinct, specific pathogenic action, without taking much ac- 

 count as to whether it corresponds exactly in one of the 

 peculiarities of length, granule staining, appearance of 

 cultures, and production of acid as given in the scheme 

 for the diphtheria bacillus. Even if several of these pecu- 

 liarities are found to differ from those in the scheme for 

 the diphtheria bacillus, still a typically pathogenic organ- 

 ism remains for us a Corynebacterium diphtherias, for clin- 

 icians have formed this species, and the single pathogenic 

 property appears so characteristic that we may build a 

 differential diagnosis upon it alone. 



It is much more difficult, if pathogenesis fails, to pro- 

 nounce regarding the relationship to the true diphtheria 

 bacillus. If all the morphologic and biologic peculiar- 

 ities are present which belong to the true diphtheria 

 bacillus, and the pathogenic property only is lacking, then 

 it is safe to decide that one is dealing with a non- virulent, 

 true diphtheria bacillus. 



It is more uncertain if, besides the virulence, still other 

 peculiarities fail; for example, the production of acid. 

 Here the decision is doubtful, and the uncertainty in- 

 creases the more peculiarities are simultaneously lacking 

 the more the organism approaches what are now cus- 

 tomarily called "bacteria resembling diphtheria." We 

 have devoted the following section to these. 



The Pseudodiphtheria Bacilli of Writers. 



Organisms resembling those of diphtheria, but not viru- 

 lent, are found in great numbers in the mouths of diph- 

 theritic and healthy persons, in the conjunctival sacs of 

 healthy and diseased eyes, etc. l Proof has not been fur- 



1 Schutz very frequently found in the sputum in tuberculosis, 

 bacilri resembling those of diphtheria (Berl. klin. Wochenschr., 1898, 



