BIOLOGICAL PROPERTIES 375 



them, this is an indication sufficiently reliable to justify a suspicion of the presence 

 of the typhoid bacillus. 



For choice, the following medium, composed by Remy and Sugg, may be used : 

 Distilled water, - - - - - 1000 c.c. 



Glucose, 



Nitrate of soda, 



Magnesium sulphate, 



Neutral phosphate of potassium, 



Calcium chloride, 



20 grams. 



10 

 2 

 1 gram. 



Inability to grow on " vaccinated " media. Chantemesse and Widal have 

 demonstrated the following curious property of the typhoid bacillus. If 

 a tube of agar or gelatin be sown with the bacillus and after incubation 

 the growth be scraped off and the medium resown with the organism the 

 second sowing remains unfertile on incubation, the medium having been, as 

 it were, " vaccinated " by the first growth. Unfortunately this phenomenon 

 sometimes fails and taken alone is not a reliable test. The colon bacillus 

 also frequently fails to grow on a medium which has been used for the growth 

 of the typhoid bacillus. 



Growth on coloured media. D'Abundo ; Nceggerath ; and also Gasser have 

 drawn attention to the property possessed by the typhoid bacillus of 

 decolourizing during growth media stained with certain dyes. 



Nceggerath's medium (p. 57) was recommended by its discoverer and later by 

 Deschamps and Grancher as a diagnostic agent for the typhoid bacillus. When 

 sown on the surface of gelatin plates coloured with Nceggerath' s fluid, the typhoid 

 bacillus gives rise to colonies of a purple colour while the surrounding medium 

 becomes decolourized. 



Gasser, recognizing that Nceggerath' s medium gives inconstant results, substituted 

 fuchsin-agar (p. 57). The typhoid bacillus sown on this medium and incubated at 

 37-39 C. for 2 days gives red colonies, the surrounding medium being decolourized. 



These reactions are unfortunately not constant and cannot be relied upon 

 for the purpose of recognizing the typhoid bacillus. 



Growth on arsenical broth. Thionot and Brouardel found that the typhoid 

 bacillus does not grow in broth containing arsenious acid to the extent of 

 0'02 gram per litre, while the colon bacillus grows not only in this medium 

 but also when the broth contains as much as 1-2 grams of arsenious acid 

 per litre. 



Growth on artichoke. According to Roget, the typhoid bacillus produces 

 no apparent growth on artichoke and does not change the colour of the 

 medium, while the colon bacillus gives a thick yellowish growth and the 

 artichoke at the same times assumes an intense green colour. 



Technique. Remove the leaves of the artichoke but leave the choke adhering to 

 the heart : cut into small cubes with a silver- bladed knife, place the cubes with the 

 choke uppermost into potato tubes containing a few drops of water in the lower 

 bulb, plug with wool and sterilize at 115 C. Sow at the junction of the choke 

 and heart. 



Growth on caffeine media. Roth has shown that the addition of 0*5 per 

 cent, of caffeine to media prevents the growth of the colon bacillus but has 

 no action on the growth of the typhoid bacillus. This characteristic is not 

 absolutely constant since some strains of the typhoid bacillus will not grow 

 in the presence of caffeine (Courmont). 



Growth on malachite-green. According to Lceffler the addition of a small 

 amount (about 1 in 4000) of malachite-green to culture media favours the 

 growth of the typhoid and paratyphoid bacilli while impeding the growth of 



