370 DIPHTHERIA. 



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 considerable confusion has arisen. 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. 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 im- 

 portant points. Some have not the same morphological and 

 staining characters in young cultures, others do not produce 

 an acid reaction in broth containing glucose; along with 

 these characters the colonies may be whiter and more 

 shining on the surface, or other minor differences in cultures 

 may be present. Such organisms have been cultivated 

 from the throat, both in the healthy condition and in non- 

 diphtheritic affections, rarely in true diphtheria along with 

 the diphtheria bacillus. The term " pseudo-diphtheritic " 

 if used at all should be applied to such organisms, but only 

 as indicating a group with the common character of 

 resemblance to the diphtheria bacillus in certain points, 

 seeing that there are more than one species. Whether 

 some of these may be really diphtheria bacilli modified by 

 certain conditions is a further question which must be con- 

 sidered undecided. The following observations may be 

 mentioned in illustration of these statements. 



