DIPHTHERIA BACILLUS. 375. 
the diphtheria bacilli. If, on the other hand, no cases 
of diphtheria have been known to exist in the neigh- 
borhood, even cases of a more suspicious nature would 
probably not be regarded as diphtheria. 
Appearances Characteristic of Diphtheria. The pres- 
ence of irregular-shaped patches of adherent grayish or 
yellowish-gray pseudomembrane on some other por- 
tions than the tonsils is, as a rule, an indication of the 
activity of the diphtheria bacilli. Restricted to the 
tonsils alone their presence is less certain. 
Occasionally, in scarlatinal angina or in severe phleg- 
monous sore-throats, patches of exudate may appear on 
the uvula or borders of the faucial pillars, and still the 
case may not be due to the diphtheria bacilli; these 
are, however, exceptional. Thick, grayish pseudo- 
membranes which cover large portions of the tonsils, 
soft palate, and nostrils are almost invariably the 
lesions produced by diphtheria bacilli. 
The very great majority of cases of psendomem- 
branous or exudative laryngitis, in the coast cities at 
least, whether an exudate is present in the pharynx or 
not, are due to the diphtheria bacilli. Cases in which 
no exudate is apparent and those in which the laryngeal 
obstruction is sudden and the spasmodic element is 
marked, are, however, frequently due to the activity of 
other bacteria. Nearly all membranous affections of 
the nose are true diphtheria. When the membrane 
is limited to the nose the symptoms are, as a rule, very 
slight; but when the nasopharynx is involved the 
symptoms are usually grave. Usually a small area of 
inflammation indicates a slight or moderate severity, 
and an extensive area a severe infection. 
Most cases of pseudomembranes and exudates entirely 
