THE HOFMANN BACILLUS 345 



sion of the Hofmann into Klebs-Loffler bacillus and vice 

 versa. Moreover, the Hofmann bacillus seemed in many 

 instances to replace the Klebs-Loffler bacillus in the throat 

 during convalescence, and it is possible in a large series of 

 cultures to obtain connecting links between the Klebs- 

 Loffler bacillus on the one hand and the Hofmann bacillus 

 on the other. Cobbett, 1 however, suggests that these 

 facts are capable of another explanation, viz. that during 

 the acute stage, diphtheria bacilli being readily found, the 

 Hofmann bacillus is likely to be overlooked, whereas at a 

 later stage a more careful search may be necessary to 

 detect the diphtheria bacillus, and the Hofmann bacillus 

 is therefore more frequently seen. 



Miss Knight and Hewlett came to the conclusion that 

 in some cases, at least, the Hofmann bacillus is a modified 

 Klebs-Loffler bacillus, and the view taken of its relation 

 to the Klebs-Loffler bacillus was, that it is a very at- 

 tenuated Klebs-Loffler bacillus, i.e. one far removed from 

 virulence. 



Salter 2 claimed to have found that the Hofmann 

 bacillus is virulent to many small birds (goldfinch, 

 chaffinch, canary, etc.), and that by successive passages 

 it becomes converted morphologically into a Klebs-Loffler 

 form with feeble virulence for the guinea-pig. He also 

 found the filtered broth culture of the Hofmann bacillus, 

 though harmless to guinea-pigs, to be toxic to smalt birds, 

 and that it contains a non -toxic substance (toxoid) which 

 has the power of combining with, and neutralising, 

 diphtheria antitoxin. Salter concluded, therefore, that 

 diphtheritic organisms are to be met with of every grade 

 of virulence, the weakest, known as Hofmann's or the 

 pseudo -diphtheria bacillus, representing the most at- 

 tenuated form of the Klebs-Loffler bacillus. The author, 



1 Journ. of Hygiene, vol. i, 1901. 



3 Trans. Jenner Inst. Prev. Med., vol, ii, p. 113. (Bibliog.) 



