438 THE DIPHTHERIA BACILLUS GROUP 
In addition to the non-virulent but morphologically typical diph- 
theria bacilli, other bacteria have been described which resemble 
B. diphtherise superficially, but differ from it in certain important 
details. Two principal types have been recognized: B. hofmanni and 
B. xerosis. They are frequently called diphtheroids.^ 
Bacillus Hofmanni.— Bacillus hofmanni appears to have been first 
observed by Loffler.'- Somewhat later Hofmann'' studied it in consider- 
able detail. 
Morphologically the Hofmann bacillus is somewhat shorter and 
relatively thicker than B. diphtheriae, and more uniform in size and 
shape. Stained with Loffler's methylene blue, but a single unstained 
area is observed typically, the organism being somewhat diplococcoid 
in form under these conditions. 
Growth is relatively more luxuriant in artificial media than that 
of the diphtheria bacillus, and no toxin is produced in sugar-free broth. 
The organism ferments no sugars, not even glucose. 
B. hofmanni is found not infrequently in normal and diseased throats, 
and occasionally in the nasal secretion. 
Bacillus Xerosis.— Bacillus xerosis, first observed by Bezold^ was 
obtained in pure culture from several cases of a chronic type of con- 
junctivitis known as xerosis by Kirschbert and Neisser.^ Since then 
the organism has been isolated repeatedly from the healthy conjunc- 
tiva and the nasal secretion. The morphological similarity between 
B. hofmanni and B. xerosis has doubtless led to confusion in the past. 
Knapp*^ has studied the fermentation reactions of the group and has 
shown that within the diphtheria group three cultural types are recog- 
nizable, as follows: 
Glucose. Saccharose. 
Bacillus diphtheriiE Acid Alkaline 
Bacillus hofmanni Alkaline Alkaline 
Bacillus xerosis Acid Acid 
Bacillus Hodgkini.— Hodgkin's disease, a malignant granulomatous 
lymi)hatic infection long regarded as a special type of infection with 
the tubercle bacillus, is now generally regarded as an infectious entity 
quite apart from tuberculosis. The etiology remained obscure until 
Negri and Mieremet'' published a description of a pleomorphic, diph- 
theroid bacillus obtained from two undoubted cases. The organism, 
which was found to be Gram-positive, received the name Corynebac- 
terium granulomatis maligni. Bunting and Yates^ have recovered 
' See Parker: Jour. Med. Res., 1922, 43, 3S7 for description of certain toxin-producing 
diphtheroids isolated from otitis media. 
2 Centralbl. f. Bakteriol., 1887, 2, 102. 
3 Ibid., 1887, 2, 543. 
4 Berl. klin. Wchnschr., 1874, 11, 408. 
5 Breslauer arztl. Ztschr., 1883, No. 4. 
« Jour. Med. Res., 1904, 12, 475. 
■ Centralbl. f. Bakteriol., orig., 1913, 68, 292. 
8 Arch. Int. Med., 1913, 12, 236; see also Bull. .Johns Hopkins Hosp., 1915, 26, 376, 
for relation of pseudodiphtheria bacilli to leukemia, pseudoleukemia and Banti's disease. 
