HOFMANN'S BACILLUS 275 



idea that Hofmann's bacillus is related to the diphtheria bacillus. But this is not 

 right, for his remarks on the pseudo-diphtheria bacillus were made in comparatively 

 early days, when the importance of acid production had not been generally recog- 

 nized and before Hofmann's bacillus had been clearly distinguished from the so-called 

 non- virulent diphtheria bacillus."] 



A. From the morphological point of view the differences between the two organisms 

 are insignificant. The pseudo-diphtheria bacillus is as a rule shorter than the 

 diphtheria bacillus but Martin has shown that this is not always the case : the length 

 of the diphtheria bacillus is subject to great variation and the variations in length 

 afford in some degree an index of its virulence. 



Too great importance must not be attached to certain characteristics said to be 

 possessed by the pseudo-diphtheria bacillus by those who consider it a distinct 

 species, and the constancy of which have not been confirmed. Deguy, for instance, 

 says that the pseudo-diphtheria bacillus is motile (?) ; according to Barbier it 

 shows no granules and stains more deeply than the diphtheria bacillus by Gram's 

 method, etc. Characteristics based upon the staining of the metachromatic granules 

 are of no value whatever for purposes of identification (p. 252). 



B. The pseudo-diphtheria bacillus occasionally produces an oedema at the site of 

 inoculation when inoculated into guinea-pigs but never leads to a fatal result. The 

 same organism may kill small birds. Roux and Yersin were able to increase the 

 virulence of an organism which produced a local oedema in guinea-pigs by mixing 

 it with a streptococcus. The virulence is therefore not a fixed quantity. 



C. Objection to the identity of the two bacilli may be taken on the ground that a 

 totally non- virulent pseudo-diphtheria bacillus has so far never been made virulent. 

 The objection, however, cannot be upheld in view of an experiment of Roux and 

 Yersin : virulent bacilli were isolated from the throat of a person suffering from 

 diphtheria ; as the patient progressed to convalescence, the bacilli became less viru- 

 lent and were finally totally avirulent and their virulence could not be restored. 



Martin has proved that some short bacilli which are not fatal to guinea-pigs are 

 degenerated diphtheria bacilli. 



Martin's experiment. An eight months old broth culture of a long, very virulent 

 bacillus was subcultivated in broth ; the organism failed to grow, but when sown 

 on agar covered with a film of recently prepared veal broth gave a growth of a short 

 bacillus which remained short in subsequent subcultivations. On inoculation, it 

 did not kill guinea-pigs but gave rise to a local oedema from which the short bacillus 

 was recovered. 



This artificially obtained short bacillus was pathogenic for sparrows, and on 

 inoculating a normal sparrow and a sparrow which had been treated with anti- 

 diphtheria serum each with O'l c.c. of a broth culture of the organism, the normal 

 sparrow died while the other survived. This short bacillus, non- virulent for guinea- 

 pigs, was therefore undoubtedly a diphtheria bacillus. 



D. In suitable culture media, non- virulent diphtheria bacilli frequently produce 

 toxin neutralizable by antidiphtheria serum (Martin). 



[In this case apparently a non- virulent diphtheria bacillus was under observation. 

 Such bacilli admittedly exist. See p. 255.] 



E. According to Spronck, a prophylactic inoculation of antidiphtheria serum 

 prevents the development of a local oedema when a diphtheria bacillus is inoculated 

 but not when a pseudo-diphtheria bacillus is inoculated. This however does not 

 appear to be a constant phenomenon. 





