404 THE DIPHTHERIA BACILLUS GROUP 



the remainder after half an hour. The first small injection indicates 

 the susceptibility of the patient; if no symptoms appear the full dose 

 may be given with impunity; even if symptoms do appear the anaphy- 

 lactic shock is aborted by the first injection and the remainder may 

 be given at the end of an hour. 



BACILLI SIMILAR TO THE DIPHTHERIA BACILLUS. 



There is a group of bacteria closely related to Bacillus diphtherise, 

 but differing from it either in virulence, morphology, or both. Certain 

 of these organisms exhibit the characteristic morphology, staining and 

 cultural reactions of the diphtheria bacillus, but do not form toxin; 

 these strains, which are occasionally found in healthy and diseased 

 throats, may be tentatively regarded as non-toxin-producing variants 

 of the type organism. 



In addition to the non-virulent but morphologically typical diph- 

 theria bacilli, other bacteria have been described which resemble 

 Bacillus diphtheria superficially, but differ from it in certain impor- 

 tant details. Two principal types have been recognized: Bacillus 

 hofmanni and Bacillus xerosis. 



Bacillus Hofmanni. Bacillus hofmanni appears to have been 

 first observed by Loffler; 1 somewhat later Hofmann 2 studied it in 

 considerable detail. 



Morphologically the Hofmann bacillus is somewhat shorter and 

 relatively thicker than Bacillus 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 dextrose. 



Bacillus hofmanni is found not infrequently in normal and diseased 

 throats, and occasionally in the nasal secretion. 



Bacillus Xerosis. Bacillus xerosis, first observed by Bezold, 3 was 

 obtained in pure culture from several cases of a chronic type of con- 

 junctivitis known as xerosis by Kirschbert and Neisser. 4 Recently 

 the organism has been isolated repeatedly from the healthy conjunc- 



1 Centralbl. f. Bakt., 1887, ii, 106. 



2 Wien. klin. Wchnschr., 1888, Nos. 3 and 4. 



3 Berl. klin. Wchnschr., 1874, p. 408. 



4 Breslauer arztl. Ztschr., 1883, No. 4. 



