210 CLINICAL BACTERIOLOGY. 



theria-bacillus generates acid. The increase in acidity is dis- 

 tinctly appreciable within twenty-four hours ; it augments from 

 the second day, then to subside. Later, after two or three weeks, 

 the bouillon becomes again alkaline. On addition of litmus to 

 the culture-medium these variations can be distinctly followed 

 by the changes in color. 



Tenacity of the Diphtheria-bacilli. A solution of 

 mercuric chlorid, I : 1000, destroys cultures in a thick 

 layer within twenty seconds ; and five per cent, potassium 

 permanganate, five per cent, aqueous solution of carbolic 

 acid, three per cent, solution of carbolic acid in thirty per 

 cent, alcohol, four per cent, solution of kresol in forty 

 per cent, alcohol, within the same time. Five per cent, 

 potassium chlorate is still ineffective after sixty seconds 

 (Loffler). Pure lemon-juice likewise destroys the bacilli 

 speedily. They are destroyed by exposure for ten minutes 

 to a temperature of 60 C. (140 F.), although in a some- 

 what thicker layer they withstand drying for months. In 

 the form of dust, however, they rapidly die. They with- 

 stand cold well, although in the refrigerator the diphtheria- 

 bacilli rapidly lose their property of generating toxins. 

 Abel found diphtheria-bacilli on building-blocks with which 

 a child suffering from diphtheria had played six months 

 previously. Diphtheria-bacilli have been found, further, 

 upon soiled bed-linen, on the rim of a drinking-glass, 

 in the hair and on the shoes of nurses, etc. In gelatin- 

 cultures they may survive, according to Loffler, for three 

 hundred and thirty-one days. Diphtheric membranes dried 

 and preserved in the dark yield cultures even after the 

 lapse of months. 



Pathogenic Properties of the Diphtheria-bacillus for 

 Animals. Diphtheria does not naturally occur in animals. 

 So-called spontaneous diphtheria of fowl, of pigeons, etc., 

 are etiologically different diseases. 



Diphtheria-bacilli give rise to the formation of true diph- 

 theric pseudomembrane, with multiplication of the bacilli, 

 in the previously injured vagina or conjunctiva of guinea- 

 pigs, in the trachea of guinea-pigs and rabbits after trache- 

 otomy. Most birds, especially pigeons and chickens, then 

 young dogs, rabbits, and especially guinea-pigs, are suscep- 

 tible to the diphtheria-bacillus. Subcutaneous introduction 

 of the bacilli is first followed by purely local alterations : 

 more or less extensive hemorrhagic edema of the subcuta- 



