THE DIPHTHERIA BACILLUS 113 



doubted that they are really diphtheria bacilli which have 

 lost their virulence. The Hofmann bacillus (' pseudo- 

 diphtheria bacillus ') differs from the Klebs-Loffler 

 bacillus in several particulars. It is a shorter, plumper, 

 somewhat spindle-shaped rod, staining pretty evenly, 

 only exceptionally presenting involution forms, and not 

 giving the Neisser staining reaction. Like the true 

 diphtheria bacillus, it stains well by Gram, and has the 

 same parallelism in arrangement. Its most marked 

 distinguishing feature is that it produces alkali and not 

 acid in milk and glucose media. It is virulent to many 

 small birds, but not to guinea-pigs, and Salter has claimed 

 that, though not forming toxin, it does form toxoids, 

 which are capable of combining with diphtheria antitoxin, 

 but his results have not been confirmed by Hewlett no 

 by Petrie. Some have believed that the Hofmann 

 bacillus is a modified and non-virulent Klebs-Loffler 

 bacillus. Most observers have failed to transform the 

 one bacillus into the other, though success has been claimed 

 in a few instances. The Hofmann bacillus seems to 

 replace the diphtheria bacillus in the fauces during 

 convalescence, and this has suggested the transformation 

 of the latter into the former. But as Cobbett pointed 

 out, diphtheria bacilli being soon found in the acute 

 stage, Hofmann bacilli might pass unnoticed, but would 

 be found when scarcity or absence of Klebs-Loffler 

 bacilli necessitated a longer microscopical examination. 

 Present opinion inclines to regard the Hofmann bacillus 

 as a species distinct from the Klebs-Loffler bacillus. In 

 view of this uncertainty, cases of ' angina,' in which the 

 Hofmann bacillus only can be isolated, are often treated 

 as infective. Van Eiemsdyk (Lancet, 1915, ii. 766) 

 says that true diphtheria bacilli inhabit the throat for 

 choice and not the nose; pseudo-diphtheria bacilli, 

 contrariwise, are most often found in the nose and rarely 

 in the throat. The Hofmann bacillus has been found 

 in the nasal mucus of as many as 71 per cent, of dwellers 

 in large towns. 



Ford Robertson believes the specific organism of general 

 paralysis to be a diphtheroid organism occurring in the cere- 

 bro-spinal fluid (B. paralyticans), and reports remissions in 

 patients by the use of a vaccine. 



The xerosis bacillus, an organism met with on the 



