DIPHTHERIA BACILLUS. 331 
pseudomembranes were produced, and frequently death 
or paralysis followed, with characteristic lesions. 
In 1887 and 1888 further studies by Loffler, Roux, 
and Yersin added to the proof of the dependence of 
diphtheria on this bacillus. It was found that while 
no other forms of bacteria were constantly. met with, 
the diphtheria bacilli were present in all characteristic 
cases of diphtheria, and that these bacilli possessed the 
morphological, cultural, and pathogenic qualities ’ of 
those described by Klebs and Léffler. The results of 
these investigations have since been confirmed by a 
great number of combined clinical and bacteriological 
observations both in animals and human beings. A 
very instructive accidental experiment was carried out 
under my observation some years ago. One of the 
laboratory workers unintentionally sucked through a 
defective pipette a few drops into the mouth of a 
bouillon culture of a virulent diphtheria bacillus, and 
two days later characteristic diphtheria of a serious type 
developed. All the conditions have been fulfilled for 
diphtheria which are necessary to the most rigid proof 
of the dependence of an infective disease upon a given 
micro-organism—viz., the constant presence of this 
organism in the lesions of the disease, the isolation of 
the organism in pure culture, the reproduction of the 
essential lesions of the disease in animals and in man 
by inoculation with pure cultures, the failure to produce 
all the characteristic lesions of this disease by any other 
bacteria, and the additional proof of the immunizing 
value of the specific substances developed in animals 
subjected to injections of diphtheria toxin. In view of 
these facts we are now justified in saying that the name 
diphtheria, or at least primary diphtheria, should be 
