376 THE TYPHOID BACILLUS 



the colon bacillus. Kiralyfi has shown that this is not a constant pheno- 

 menon : according to this observer though malachite-green inhibits the 

 growth of many micro-organisms e.g. streptococci, staphylococci, vibrio 

 cholerse, it generally has no action on the colon bacillus. 



Krystal-violet has the same action as malachite-green (Drigalski and Con- 

 radi) : both typhoid and colon bacilli grow on media containing this dye while 

 the growth of many other organisms is inhibited. 



2. Variability of flagella. 



Sunlight, antiseptics in dilute solution and temperatures unsuitable to 

 growth have practically no influence on the number and shape of the flagella 

 (Kemy and Sugg). When the typhoid bacillus has been grown in culture 

 with the colon bacillus for some weeks the flagella are sometimes difficult to 

 stain (Kemy). The rarity of variation in the morphology of the flagella 

 is of importance in diagnosing the typhoid bacillus. 



3. Viability and virulence. 



Viability. Exposure to a temperature of 60 C. kills the typhoid bacillus 

 in 10-20 minutes but very low temperatures have no effect on its vitality ; 

 thus, Prudden found the organism still alive in a block of ice which had been 

 kept for 3 months between - 1 and - 11 C. On the other hand, alternate 

 freezing and thawing rapidly kills the bacillus. 



In water, the typhoid bacillus retains its vitality for some time (Strauss 

 and Dubarry, Chantemesse and Widal). In sterile water it has been found 

 to be alive after 3 months. If the water contains saprophytic micro-organisms 

 the typhoid bacillus disappears more quickly, but it can still be isolated after 

 more than 1 month. 



In soil, the bacillus can survive five months and a half (Grancher and 

 Deschamps) : drying kills it only after 1 or 2 months (UfFelmann). Levy 

 and Kaiser isolated the organism from stools which after being in a cesspool 

 for 5 months had been spread on the surface of the ground for 15 days in 

 winter. 



Light rapidly kills the typhoid bacillus. Cultures exposed to sunlight in 

 the month of May were sterilized in 48 hours. Vincent has found that the 

 blue, violet and ultra-violet rays are more efficient as bactericidal agents 

 than the red and ultra-red rays. Cultures spread and dried on pieces of 

 cloth, and then exposed to direct sunlight, were found to be sterilized in 

 9-26 hours (Vincent). 



The typhoid bacillus is very sensitive to the action of antiseptics : the 

 solutions of perchloride of mercury, carbolic acid, etc. in general use will 

 kill the bacillus in a few minutes. 



Virulence. The great variations observed in the virulence of the typhoid 

 bacillus and the methods by which the virulence can be raised have already 

 been studied under the head of experimental inoculation. 



4. The toxin of the typhoid bacillus. 



The experiments conducted by Brieger and Fraenkel with a view to isolating 

 a toxin from the typhoid bacillus gave very little result. Attempts are now 

 no longer made to extract a definite chemical substance from cultures. The 

 crude toxin found in sterilized cultures has been studied by Sanarelli, Chante- 

 messe and others. Other observers (Macfadyen and Rowland, Besredka and 

 others) have prepared extracts containing an endotoxin from the bodies of 

 the organisms, 



