PATHOGENIC SPIRILLA. 505 



Bolton's experiments (1887) mercuric chloride was effective in two 

 hours in the proportion of 1 : 10,000 ; sulphate of copper, 1 : 500. 



The low thermal death-point and comparatively slight resisting 

 power for desiccation and chemical agents indicate that this spiril- 

 lum does not form spores, and most bacteriologists agree that this 

 is the case. Hueppe, however, has described a mode of spore for- 

 mation which is different from that which occurs among the bacilli, 

 viz. , the formation of so-called arthrospores ; these are said to be 

 developed in the course of the spiral threads, not as endogenous re- 

 fractive spores, but as spherical bodies which have a somewhat 

 greater diameter than the filament and are somewhat more refrac- 

 tive. This mode of spore formation has not been observed by Kita- 

 sato and other bacteriologists who have given attention to the ques- 

 tion, and cannot be considered as established. In competition with 

 the ordinary putrefactive bacteria the cholera spirillum soon disap- 

 pears, and, as determined by Neffelman and by Kitasato, they only 

 survive for a few days when mixed with normal fseces. 



A test for the presence of the cholera spirillum has been found 

 by Bujwid and by Dunham in the reddish-violet color produced in 

 bouillon cultures containing peptone, or in cultures in nutrient gela- 

 tin, when a small quantity of sulphuric acid is added to the culture. 

 According to Frankel, this test serves to distinguish it from the ordi- 

 nary bacteria of the intestine and from the Finkler-Prior spirillum, 

 but not from Metschnikoff's spirillum (" vibrio "). The reaction is 

 shown by bouillon cultures which have been in the incubating oven 

 for ten or twelve hours, and by gelatin cultures in which liquefac- 

 tion has occurred. The sulphuric acid used should be quite pure ; 

 the color quickly appears and is reddish- violet or purplish-red. Ac- 

 cording to Salkowski, the red color is due to the well-known indol 

 reaction, which in cultures of the cholera spirillum is exceptionally 

 intense and rapid in its development. A test which is said to dis- 

 tinguish cultures of the cholera spirillum from the spirillum of De- 

 neke and that of Finkler-Prior, has been proposed by Cahen. This 

 consists in adding a solution of litmus to the bouillon and in making 

 the culture at 37 C. The cholera cultures show on the following 

 day a decoloration which does not occur at this temperature with the 

 other spirilla named. 



For determining as promptly as possible whether certain suspected 

 excreta contain cholera spirilla, a little of the material may be used 

 to inoculate greatly diluted bouillon, gelatin plates being made at 

 the same time. At the end of ten or twelve hours the cholera spiril- 

 lum, if present, will already have formed a characteristic wrinkled 

 film upon the surface ; a little of this should be used to start a new 

 culture in diluted bouillon, and a series of gelatin plates made from 



