BACTERIA IN DIPHTHERIA. 461 
Park and Beebe (1894), in an extended research made for the pur- 
pose of determining the persistence of the diphtheria bacillus in the 
throats of convalescents (2,566, cultures made), found that in 304 out 
of 605 consecutive cases the bacillus disappeared within 3 days after 
the disappearance of the exudate; in 176 cases it persisted for 7 days; 
in 64 cases for 12 days; in 36 cases for 15 days; in 12 cases for 3 
weeks; in 4 cases for 4 weeks; in 2 cases for 9 weeks. Park and 
Beebe arrive at the following conclusion with reference to pseudo- 
diphtheria bacilli: 
“The name pseudo-diphtheria bacillus should be regarded as ap- 
plying to those bacilli found in the throat which, though resembling 
the diphtheria bacilli in many respects, yet differ in others equally im- 
portant. These bacilli are rather short, and more uniform in size 
and shape than the typical Léffler bacillus. They stain equally 
throughout with the alkaline ‘methyl-blue solution, and produce 
alkali in their growths in bouillon. They are found in about one 
per cent of the healthy throats in New York City, and seem to have 
no connection with diphtheria. They are never virulent.” 
Park (1894) has shown that virulent diphtheria bacilli are fre- 
quently found in the throats of persons who have been associated 
with diphtheria patients, although no manifestations of the disease 
were visible. It is therefore apparent that infection requires not 
only the presence of virulent bacilli, but also of a predisposition to 
the disease. This corresponds with the facts relating to other in- 
fectious diseases—e.g., tuberculosis, typhoid fever—and among’ the 
probable predisposing causes we may mention “sewer-gas poisoning,” 
catarrhal inflammations of the mucous membranes most commonly 
involved, inanition, “crowd poisoning,” and depressing agencies 
generally. 
Bacteriologists have given much attention to the question of mixed 
infection in diphtheria. Funck (189+) accepts the generally received 
view that mixed infections with the diphtheria bacillus and Strepto- 
coccus pyogenes are more serious than an uncomplicated diphtheria, 
and in an experimental research has attempted to determine whether 
this is due to an increased production of the diphtheria bacillus or to 
the presence of the streptococcus. His experiments on guinea-pigs 
showed that when infected with streptococci these animals did not 
prove to be more sensitive to the action of the diphtheria poison 
(without living bacilli), and he concludes that the unfavorable influ- 
ence of the streptococcus in mixed infections is due to increased patho- 
genic activity on the part of the diphtheria bacillus. Bernheim 
(1894) found, in his experiments on guinea-pigs, that they suc- 
cumbed more rapidly to diphtheria infection when they previously 
