238 BACTERIA PATHOGENIC TO MAN 



EFFECT OF COLON BACILLI IN NITROGENOUS COMPOUNDS. Colon 

 bacilli do not appreciably liquefy gelatin nor peptonize any albumins. 

 They do, however, break down some of the higher nitrogenous com- 

 pounds into smaller atom groups. The first noted of these compounds 



was indol, C 6 H 4 v rr / CH. This is one of the most important products 



of colon activity, although a few varieties lack it. (Witte's peptone solu- 

 tion is used as test.) Sugars interfere with indol production, as also does 

 the absence of oxygen. The maximum amount of indol is present 

 about the tenth day. The test is carried out by adding 1 c.c. of 0.02 

 per cent, potassium nitrite to 10 c.c. of culture fluid, and then some 

 concentrated sulphuric acid. To prevent confusion with other colors a 

 little amyl alcohol is added and shaken. In the intestinal canal in health 

 very little indol appears to be produced by colon bacilli. Sulphuretted 

 hydrogen is liberated from sugar-free fermentable proteid substances. 

 Mercaptan and sometimes skatol have been noted in peptone solution 

 cultures. The colon bacillus liquefies minute quantities of gelatin, but 

 so little as to be inappreciable. 



The colon bacillus can make use of simpler nitrogen compounds 

 than the typhoid bacillus, and can grow well in media such as that of 

 Uschinsky. In urine some colon cultures produce a slight fermentation, 

 yielding ammonium carbonate. By some this is believed not to be due 

 to urea fermentation. Lactose-litmus-urine agar, after twenty-four 

 hours' acidity, often becomes alkaline. 



In media containing fermentable sugars and proteid substances 

 simultaneous action takes place on both with the production of both 

 alkalies and acids. 



Effect on Fats. No action has been noted. 



Reduction Processes. REDUCTION OF PIGMENTS. The action on 

 certain pigments which are reduced to colorless products and interme- 

 diate colors is more vigorous than that of typhoid bacilli. This effect 

 occurs in litmus bouillon in the closed arm of the tube, in bouillon 

 and agar (not in gelatin), indigo-sodium-sulphate-methyl blue, in sugar 

 media, etc. 



REDUCTION OF INORGANIC SALTS. From nitrates coli under certain 

 conditions produce nitrites and from them free nitrogen as follows: 

 2NaN0 3 + H 2 O = 2NaOH + N 2 + O 5 . 



The development of pigments (brownish, greenish, and yellowish), 

 odorous substances, and toxins has been noted, especially on potato. 

 Besides ammonia and the fatty and oxy-fatty acids other bad -smelling 

 products, but little understood, are formed at times. 



Toxins. The bodies of dead colon bacilli contain pyogenic substances, 

 and others which, injected into the circulation, produce paralysis of the 

 striped muscle fibres, convulsions, coma, and death. Extracts from 

 some cultures produce irritation of the mucous membranes of the large 

 intestines with dysenteric symptoms. 



Growth with Other Bacteria. Colon bacilli grown with typhoid bacilli 

 are hindered in 'their gas production and indol formation, while the 



