398 THE COLON BACILLUS 



Nceggerath's medium and fuchsin-agar. The typhoid bacillus gives similar 

 results. 



7. Growth on arseniated broth. A typical colon bacillus grows in broth 

 containing as much as 2 grams of arsenious acid per litre (Thoinot and 

 Brouardel). 



8. Growth on artichoke. A typical colon bacillus grows luxuriantly on 

 artichoke, and turns the medium green (p. 375). 



9. Growth on media containing caffeine. The colon bacillus does not 

 grow on media containing 0*5 per cent, of caffeine (p. 408). 



10. Growth on malachite-green media. According to Loeffler the addition 

 of a small quantity of malachite-green to culture media prevents the growth 

 of the colon bacillus, but does not interfere with the growth of the typhoid 

 bacillus. As a matter of fact, the colon bacillus grows on media containing 

 either malachite green or crystal violet (pp. 409 and 407). 



2. Variability of flagella. 



The variability of the flagella is very limited, their characteristics being 

 little influenced by antiseptics, temperatures unfavourable to growth, etc. 

 (Kemy and Sugg). 



Examination of the flagella should never be neglected when it is desired to 

 identify the colon bacillus. 



3. Vitality and Virulence. 



Vitality. All that has been said with regard to the vitality of the typhoid 

 bacillus is equally applicable to the colon bacillus. 



Virulence. The virulence of the colon bacillus is subject to great variation 

 (vide experimental inoculation, p. 394). 



4. Toxin. 



Malvos has shown that porcelain-filtered broth cultures are toxic. Broth 

 cultures also yield a toxic precipitate when heated with sulphate of ammonia. 

 As a rule, the toxin is not very harmful and large doses of filtered cultures 

 must be inoculated to produce a fatal result in experimental animals. 



The inoculation of a large dose of toxin into the ear- vein of a rabbit pro- 

 duces the following symptoms : At first there is muscular weakness, sub -normal 

 temperature, drowsiness and coma : later, convulsions set in and finally a 

 generalized tetanic condition which continues till the animal dies (Gilbert). 

 A smaller dose produces a chronic intoxication with diarrhoea, drowsiness 

 and wasting, the animal often dying of cachexia. 



In guinea-pigs, the inoculation of large quantities of toxin into the peri- 

 toneal cavity is followed by a sub-normal temperature and leads to collapse 

 and death (Boix). The blood may contain organisms (especially the colon 

 bacillus) which have found their way from the intestinal canal (Achard and 

 Renault). 



Colilysin. In suitable media the colon bacillus forms an haemolytic sub- 

 stance (Kayser). 



Colilysin is only produced in any quantity if the broth has a markedly acid 

 reaction (80 c.c. of decinormal oxalic acid per litre). 



The hsemolysin is present after incubating for 2 days at 37 C. but continues to 

 increase in amount until the fourth day and remains at its maximum until the end 

 of the second week. 



Colilysin is a powerful solvent of dog red-cells ; it has less action on horse, 

 ox, and rabbit cells, and very little and in some cases no action at all on the 



