BACTERIA IN DIPHTHERIA. 451 
that we were two years ago, owing to the large number of important re- 
searches which have been made in the interim, in saying that the name 
diphtheria, or at least primary diphtheria, should be applied, and exclusively 
applied, to that acute infectious disease, usually associated with a pseudo- 
membranous inflammation of the mucous membranes, which is primarily 
caused by the bacillus called Bacillus diphtheriz of Loffler.” 
With reference to the question as to how long after convalescence 
is estabiished the diphtheria bacillus may be present in the throat 
of an infected person, Léffler has made the following research (1890). 
In a typical case a bacteriological examination was made daily from 
the commencement until fourteen days after its termination. Fever 
disappeared on the fifth day, and the exudation had all disappeared 
on the sixteenth day. Up to this time the bacillus was daily ob- 
tained in cultures, and subsequently nearly every day up to the 
twenty-fifth—that is, for three weeks after the febrile symptoms had 
disappeared. Roux and Yersin have also obtained the bacillus in 
cultures from mucus scraped from the throats of convalescents sev- 
eral days after the disappearance of all evidence of the disease. 
Seconp. The Klebs-Léffler bacillus is found only in diph- 
theria.—In his earlier researches Léffler obtained the bacillus in a 
single instance from the mouth of a healthy child, and this fact led 
him to hesitate in announcing it as his conviction that it was the 
true cause of diphtheria. Butin extended researches made subse- 
quently he has not again succeeded in finding it, except in associa- 
tion with diphtheria, and admits now that he may have been mis- 
taken as to the identity of the bacillus found. This seems not 
improbable in view of the fact that very similar bacilli have been 
found by various bacteriologists. Thus Von Hoffmann obtained a 
very similar but non-pathogenic bacillus from the mucus of chronic 
nasal catarrh and from healthy mucous membranes; Babes from 
cases of trachoma, Neisser from ulcers, Zarinko from the surface of 
various mucous membranes. But all of these were shown to present 
certain differences in their biological characters by which they could 
be differentiated from the true diphtheria bacillus. 
Welch and Abbott in their comparative studies did not find the 
Léffler bacillus, “‘or any bacillus that an experienced bacteriologist 
would be likely to confound with it.” They examined mucus from 
the throats of healthy children, from those suffering from simple in- 
flammation of the tonsils and pharynx, and from four cases of so- 
called follicular tonsillitis. As a result of their investigations they 
agree with Léffler, and with Roux and Yersin, as to “the great prac- 
tical value, for diagnostic purposes, of a bacteriological examination 
of cover-glass specimens and by cultures” of cases in which there is 
any doubt of the true character of the disease. They say further : 
