Til !'- HACILLl'S A \ D THE BA C TERIOLOG Y OF DIPH THERIA 20 1 



authors state that there is generally a sequence of types in the varia- 

 tions which appear throughout the course of the disease, the granular 

 types being the most predominating at the outset of the disease, and 

 these giving place wholly or in part to the barred and solid types shortly 

 before the disappearance of diphtheria-like organisms. 



The inference drawn from this work is that the diphtheria bacillus 

 may be rather easily, especially in the throat, converted into non- 

 granular, solidly staining forms of the " pseudodiphtheria" type, and 

 that the converse may occur, and that therefore all diphtheria-like 

 bacilli must be considered a possible source of danger. 



Cobbett 1 considers the pseudodiphtheria bacillus as perfectly innocu- 

 ous to man, but that the relation between the pseudodiphtheria and 

 the diphtheria bacillus remains undecided. He did not meet with bacilli 

 of low virulence. He found a few non-virulent and the others were all 

 highly virulent. He thinks that the reason why the pseudodiphtheria 

 bacilli appear so infrequently during the acute stage is that they are 

 overlooked then because one discovers the virulent bacilli so easily 

 and does not trouble to look any more, and they are found more easily 

 later because the diphtheria bacilli are disappearing and are hard to 

 find; consequently a long and careful search is made, and the pseudo- 

 diphtheria bacilli are seen for the first time. 



All of this work (including the reports of observers not mentioned 

 in this paper) in regard to the relationship of the different diphtheria- 

 like bacilli to the true diphtheria bacillus may be summed up and 

 tabulated as follows: 



Statements in favor of the belief that one form Statements opposed to this belief, 



may be changed readily into another. 



1. The morphological and cultural char- The morphological and cultural charac- 



acteristics of all diphtheria-like teristics of varieties have many points 



organisms from pseudo to typical of difference, 



virulent forms have some points of 

 resemblance. 



2. Diphtheria bacilli possess many Intermediate grades of virulence are rare. 



grades of virulence from the fully 

 virulent to the non-virulent. 



3. Non-virulent bacilli, both typical and There are other reasons than that of 



non-typical, have been found more change of one form to another to 



frequently in the convalescing stage account for this, 

 of diphtheria than in the acute stage. 



4. Non-virulent, atypical bacilli have Virulent diphtheria bacilli have also been 



been the only diphtheria-like organ- frequently found, 



isms found in light anginas. 



5. A sequence of forms in the course of The observation is correct only for the 



diphtheria and in successive genera- forms in the original mixed cultures 



tions of pure cultures, from granular and is due to the effect of the other 



through barred to solid forms, and bacteria on the development of the diph- 



the converse, has been observed. theria bacilli or because both varieties 



were present at the start. 



i Journal of Hygiene, 1901. 



