BACTERIUM DIPHTHERIA 495 



Clinically, membranous rhinitis is never such an alarming 

 disease as is laryngeal or pharyngeal diphtheria, and, as 

 stated, the organisms causing it are often of a low degree of 

 virulence, though they are, nevertheless, genuine diphtheria 

 bacteria. 



For those organisms that are in all respects identical with 

 the virulent bacillus diphtherise, save for their inability to 

 kill guinea-pigs, the designation " pseudodiphtheritic bacil- 

 lus" is usually employed; but from such observations as 

 those just cited we are inclined to the opinion that pseudo- 

 diphtheritic, as applied to an organism in all respects iden- 

 tical with the genuine bacterium, except that it is not fatal 

 to susceptible animals, is a misnomer, and that it would 

 be more nearly correct to designate this organism as the 

 attenuated or non-virulent diphtheritic bacterium, reserving 

 the terms "pseudodiphtheritic" or " diphtheroid " for that 

 organism or group of organisms (for there are probably 

 several) that are enough like the diphtheria bacterium to 

 attract attention, but is distinguishable from it by certain 

 morphological and cultural peculiarities aside from the 

 question of virulence. 



It is a well-known fact that many pathogenic organisms 

 conspicuous among these being bacterium pneumoniae, 

 micrococcus aureus, streptococcus pyogenes, and the group 

 of so-called "hemorrhagic septicemia" organisms undergo 

 marked variations in their pathogenic 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 varieties, the virulence of 

 which, from various causes, has been modified. 



It must nevertheless be admitted that in the course of 



