370 DIPHTHERIA. 



with streptococci, inoculation of the bacilli alone not being suc- 

 cessful for this purpose. If, however, the virulence had fallen 

 very low, even the presence of the streptococci was insuificient 

 to restore it. As a rule, the cultures most virulent to guinea- 

 pigs are obtained from the gravest cases of diphtheria, though 

 to this rule there are frequent exceptions. It has been abun- 

 dantly established that after the cure of the disease, the bacilli 

 may persist in the mouth for weeks and months, though they 

 often quickly disappear. Roux and Yersin found, by making 

 cultures at various stages after the termination of the disease, 

 that these bacilli in the mouth gradually become attenuated. 

 These observations are of importance in relation to the subject 

 of the pseudo-diphtheria bacillus. At present it would scarcely 

 be safe to make a definite statement as regards the relation of 

 virulence to the size of the bacilli. Perhaps the majority of 

 observers have found that the bacilli of the larger form are 

 usually more virulent than those of the shorter form ; but this 

 is not invariably the case, as sometimes short forms are obtained 

 which possess an extremely virulent character. Both the long 

 and the short forms may become attenuated in the same way. 



The so-called Pseudo-diphtheria Bacillus. — Under this term 

 more than one species of bacillus has been described and con- 

 siderable confusion has arisen, {a) The name has been applied 

 by some observers to an organism differing from the diphtheria 

 bacillus solely in its want of virulence. Such an organism must 

 be regarded merely as the diphtheria bacillus in an attenuated 

 condition, and should be spoken of as such, {b') On the other 

 hand, there have been cultivated several species of bacilli which 

 resemble the diphtheria bacillus in some respects, but differ from 

 it in certain important points. They have not all the morpho- 

 logical and staining characters in young cultures, and do not 

 produce an acid reaction in broth containing glucose ; along 

 with these characters minor differences in cultures may be 

 present. Such organisms have been cultivated from the throat, 

 both in the healthy condition, in non-diphtheritic affections, 

 and also in true diphtheria along with the diphtheria bacillus. 

 The term "pseudo-diphtheria" if used at all should be applied 

 to such organisms. The type most commonly met with is a 

 shorter bacillus than the diphtheria bacillus, with usually a 

 single unstained septum running across it, though sometimes 



