354 BACTERIOLOGY. 
hacillus is absent. This, or one similar to it, has been 
described by Vincent.’ It does not grow on artificial 
media and is not pathogenic in animals. From its 
presence in the false membrane of a number of cases, 
it is believed to have some causal relation to them. 
_ These cases show most of the local appearances of 
true diphtheria, the superficial necrosis of the epithe- 
lium, the membrane of the glandular swellings. The 
pseudomembranes may persist for from one to two 
weeks, or even, in exceptional cases, longer. This 
bacillus is apparently frequently present in the normal 
throat, and is probably only able under certain favor- 
ing conditions, such as syphilis, to produce lesions. 
Nerve degeneration and paralysis do not follow an 
attack. 
The pseudomembranous angina accompanying scarlet 
fever, and to a less extent other diseases, may not 
show the presence of diphtheria bacilli, but only the 
pyogenic cocci, especially streptococci, or, more rarely, 
some varieties of little known bacilli. The deposit 
covering the inflamed tissues in these non-specific cases 
is, it is true, usually but not always, rather an exudate 
than a true pseudomembrane. The majority of these: 
cases, however, are mild affections, being only of im- 
portance in adding to the severity of the disease which 
they complicate. An exception should be made when 
the larynx is affected, as here the lungs are often sec- 
ondarily involved. The bacteria which occur in false 
diphtheria are streptococci, staphylococci, diplocosci, 
and sometimes pseudodiphtheria bacilli or bacilli which 
are morphologically and culturally distinct from the 
1 Annales de l'Institut Pasteur, August, 1899. 
