DIPHTHERIA BACILLUS. 353 
the streptococcus being particularly active in this 
respect, often opening the way for the invasion of the 
Loffler bacillus into the deeper tissues or supplying 
needed conditions for the development of its toxin. 
Thus diphtheria is not always a primary, but often a 
secondary disease, following some other infection, as 
measles or scarlet fever. In most fatal cases of bron- 
chopneumonia following laryngeal diphtheria we find 
not only abundant pneumococci or streptococci in the 
inflamed lung areas, but also in the blood and tissues 
of the organs. As these septic infections due to the 
pyogenic cocci are in no way influenced by the diph- 
theria antitoxin, they frequently are the cause of the 
fatal termination. Other bacteria cause putrefactive 
changes in the exudate, producing alterations in color 
and offensive odors. 
Pseudomembranous Exudative Inflammations Due to 
Bacteria other than the Diphtheria Bacilli. The diph- 
theria bacillus, though the most usual, is not the only 
micro-organism that is capable of producing pseudo- 
membranous inflammations. There are numerous bac- 
teria present almost constantly in the throat secretions, 
which, under certain conditions, can cause local lesions 
very similar to those in the less marked cases of true 
diphtheria. The streptococcus and pneumococcus are 
the two forms most frequently found in these cases, 
but there are also others which, under suitable condi- 
tions, take an active part in producing this form of 
inflammation. Some of these bacteria do not develop 
on artificial media, so that we know little of their 
characteristics. Among these is a long slender bacillus 
which is occasionally found in great abundance in the 
middle layers of pseudomembranes when the diphtheria 
23 
