344 A MANUAL OF BACTERIOLOGY 



granular deposit, sometimes a general turbidity. On 

 neutral litmus glucose-agar and in litmus milk a blue 

 colour is developed, indicating the production of alka- 

 linity ; milk is not curdled. Cultivated in peptone water 

 an indole-like reaction with sulphuric acid alone can be 

 obtained after a variable time, three to four weeks, while 

 the diphtheria bacillus gives it in about a week ; with a 

 nitrite and sulphuric acid the indole-like reaction can be 

 obtained with both the pseudo- and diphtheria bacilli 

 in about a week. The substance giving this indole-like 

 reaction is not indole, but skatole-carboxylic acid. 1 A 

 broth culture reduces a weak solution of methylene blue. 

 The Hofmann bacillus is non-pathogenic to guinea-pigs 

 in doses of 5 c.c. or more of a forty-eight hours' broth 

 culture, but is stated to be virulent to certain birds (see 

 below). Mandelbaum and Heinemann 2 state that if a 

 glycerin-agar plate be smeared with human blood and 

 inoculated, the diphtheria bacillus produces colonies 

 surrounded by a yellow zone, while the colonies of the 

 Hofmann and xerosis bacilli do not change the red colour 

 of the blood. In addition, the Hofmann bacillus does not 

 ferment any sugar, etc. (see table, p. 348). 



The histories of several cases investigated by Miss 

 Knight and Hewlett seemed to show that the Hofmann 

 bacillus is associated with mild anginal conditions, which 

 are free from complications, end in recovery, and are not 

 followed by sequelae. In many of the cases the anginal 

 condition was associated with distinct patches of mem- 

 brane, and in two symptoms were present suggestive of 

 the toxaemia which is met with in diphtheria. 



In a long series of experiments Hewlett and Miss Knight 

 believed that some evidence was obtained of the conver- 



1 Hewlett, Trans. Path. Soc. Lond., vol. li, 1900, p. 187 ; vol. lii, 1901, 

 p. 113. 



* Centr. f. Bakt. (Orig.), liii, 1910, p. 536, 



