450 BACTERIA IN DIPHTHERIA. 
obtained it in pure cultures, and by inoculations in pigeons, chickens, 
rabbits, and guinea-pigs proved that it gave rise to a diphtheritic 
inflammation when inoculated into the mucous membrane of the 
trachea, conjunctiva, pharynx, or vagina. In a second communica- 
tion Léffler reported his success in finding the same bacillus in ten 
additional cases, and also that he had isolated from the same source 
a non-pathogenic bacillus which resembled it very closely. This 
pseudo-diphtheria bacillus has since been found by other bacteri- 
ologists (Von Hoffmann, Roux and Yersin), and it is uncertain 
whether it is to be considered a distinct species, or a non-pathogenic 
variety of the diphtheria bacillus as maintained by Roux and Yersin. 
But its occasional presence does not invalidate the very positive ex- 
perimental evidence relating to the specific pathogenic power of the 
true diphtheria bacillus. 
Léffler, in 1890, reviewed the evidence upon which this bacillus is 
now generally conceded by bacteriologists to be the specific infectious 
agent in true diphtheria. The following are the principal points in 
the demonstration : 
First.—It is found in all undoubted cases of diphtheria, In 
support of this we have the results of researches made by Léffler, 
Wyssokowitsch, D’Espine, Von Hoffmann, Ortmann, Roux and 
Yersin, Kolisko and Paltauf, Zarinko and Sérensen, who in nearly 
every case have demonstrated without difficulty the presence of this. 
bacillus. On the other hand, Prudden failed to find it in a series of 
twenty-four cases studied by him; but his own account of these 
cases indicates that they were not cases of true diphtheria. He says 
in a subsequent communication : 
“In view of the doubt existing among practitioners as. to whether all 
forms of pseudo-membranous inflammation should be called diphtheria or 
not, and with the purpose of making a wholly objective study, the writer 
distinctly stated at the outset of that paper that all the fatal cases of exten- 
sive pseudo-membranous laryngitis, as well as pharyngitis, should in his 
study be considered as cases of diphtheria. This left the question as to the 
propriety of establishing separate groups of pseudo-membranous inflamma- 
tion open and free from bias. It was distinctly stated, however, that six- 
teen out of the twenty-four cases occurred in a large asylum, in which 
measles and scarlet fever were prevalent during the period in which these 
studies were under way. Five other cases in another asylum were ex- 
posed to similar conditions.” 
In a subsequent series of “‘ twelve cases of fatal pseudo-mem- 
branous inflammation occurring in two children’s asylums, in which 
for many months there had been no scarlatina and no measles, and 
in which there was no complicating suppurative inflammation and 
no erysipelas,” Prudden (1890) obtained Léffler’s bacillus in cultures 
from eleven, and he says: 
‘‘We are now, it would seem, justified, as it did not appear to the writer 
