Till- HACILLUS AXD THE BACTERIOLOGY OF DIPHTHERIA 197 



catarrhal inflammations of the mucous membranes, and depressing 

 conditions generally. Under these conditions an infected mucous mem- 

 brane may become susceptible to disease. In connection with Beebe 

 (1894) I made an examination of the throats of 330 healthy persons 

 who had not come in contact, so far as known, with diphtheria, and 

 we found virulent bacilli in 8 only, 2 of whom later developed the dis- 

 ease. In 24 of the 330 healthy throats non-virulent bacilli or attenuated 

 forms of the diphtheria bacillus were found. Very similar observations 

 have been made by others in many widely separated countries. 



Persistence of Diphtheria Bacilli in the Throat. The continued pres- 

 ence of virulent diphtheria bacilli in the throats of patients who 

 have recovered from the disease, and after the disappearance of the 

 exudate, has been repeatedly demonstrated. Beebe and I found that 

 in 304 of 605 consecutive cases the bacilli disappeared within three 

 days after the disappearance of the pseudomembrane ; in 176 cases 

 they persisted for seven days, in 64 cases for twelve days, in 36 cases 

 for fifteen days, in 12 cases for three weeks, in 4 cases for four weeks, 

 and in 2 cases for nine weeks. Since then I have met with a case in 

 which they persisted with full virulence for eight months. Later figures 

 agree substantially with these. 



Pseudodiphtheria Bacilli. Besides the typical bacilli which produce 

 diphtheria toxin and those which do not, but which, so far as we can 

 determine, are otherwise identical Avith the Loeffler bacillus, there are 

 other bacilli found in positions similar to 

 those in which diphtheria bacilli abound, 

 which, though resembling these organisms 

 in many particulars, yet differ from them as 

 a class in others equally important. The 

 variety most prevalent is rather short, plump, 

 and more uniform in size and shape than 

 the true Loeffler bacillus (Fig. 83). On 

 blood-serum their colony growth is very 

 similar to that of the diphtheria bacilli. 

 The great majority of them in any culture 

 show no polar granules when stained by the 



x ^ . . J Pseudodiphtheria bacilli. 



Neisser method, and stain evenly through- 

 out with the alkaline methylene-blue solution. They do not produce 

 acid by the fermentation of glucose, as do all known virulent and many 

 non-virulent diphtheria bacilli; therefore, there is no increase in acidity 

 in the bouillon in which they are grown during the first twenty-four 

 hours from the fermentation of the meat-sugar regularly present. They 

 are found in varying abundance in different localities in New York 

 City, in about 1 per cent, of the normal throat and nasal secretions, 

 and seem to have now at least no connection with diphtheria; whether 

 they were originally derived from diphtheria bacillus is doubtful; they 

 certainly seem to have no connection with it now. They never pro- 

 duce diphtheria toxin, and to them properly has been applied the name 

 psendodiphtheria bacilli. In bouillon they grow, as a rule, less luxuri- 



