BACTERIUM PSEUDODIPHTHERIT1CUM. 415 



diphtheria bacterium to attract attention, but is distin- 

 guishable from it by certain morphological and cultural 

 peculiarities aside from the question of virulence. 



It is a well-known fact that many pathogenic organ- 

 isms conspicuous among these being bacterium pneu- 

 monias, micrococcus aureus, streptococcus pyogenes, and 

 the group of so-called " hemorrhagic septicaemia " 

 organisms undergo marked variations in their patho- 

 genic properties ; and yet these organisms, when found 

 either devoid of this peculiarity, or possessing it in a 

 diminished degree, are not designated as " pseudo " 

 forms, but simply as the organisms themselves, the viru- 

 lence of which, from various causes, has been modified. 



It must nevertheless be admitted that in the course 

 of microscopic examination of materials from various 

 sources, including the pharynx, one occasionally encoun- 

 ters micro-organisms whose morphology is so like that 

 of the genuine bacterium diphtherice as to create suspi- 

 cion, and yet they are at the same time sufficiently 

 unlike it to make one cautious in forming an opinion 

 as to their real nature. 



BACTERIUM PSEUDODIPHTHERITICUM. For a long 

 time bacterium pseudodiphtheriticum was looked upon as 

 being entirely harmless, and the only particular in which 

 it was regarded as being of importance was in the fact 

 that it was likely to be mistaken for bacterium diph- 

 therias. The wide dissemination of this class of organ- 

 isms and the demonstration of pathogenic effects in iso- 

 lated instances has led to the more systematic study of 

 members of this group of organisms. 



Bacterium pseudodiphtheriticum, as found under dif- 

 ferent conditions, varies markedly in its morphologic 

 and biologic characters. Some of the varieties have 



