. Pharmaceutical bacteriology, with special reference to disinfection and sterilization. Bacteriology. 68 PHARMACEUTICAL BACTERIOLOGY. If the temperature and color differential tests indicate sewage contamina- tion, then the following additional tests should be carried out. III. Indol Reaction and Gas Formula.—The indol reaction has already been explained. The gas formula is determined as follows: To sets of four grad- uated fermentation tubes containing glucose bouillon and lactose bouillon, add , , , and 10 of the suspected liquid. If gas formation is observed the presence of c
. Pharmaceutical bacteriology, with special reference to disinfection and sterilization. Bacteriology. 68 PHARMACEUTICAL BACTERIOLOGY. If the temperature and color differential tests indicate sewage contamina- tion, then the following additional tests should be carried out. III. Indol Reaction and Gas Formula.—The indol reaction has already been explained. The gas formula is determined as follows: To sets of four grad- uated fermentation tubes containing glucose bouillon and lactose bouillon, add , , , and 10 of the suspected liquid. If gas formation is observed the presence of colon bacilli may be suspected. If the tubes show gas formation then the presence of colon bacilli may be assumed. Fill the bulb of a tube, showing gas formation, with a 2-per cent, solution of sodic hydrate, hold thumb tightly over the opening and mix contents by tilting back and forth carefully. The portion of gas absorbed is CO2 whereas the unabsorbed portion is supposedly hydrogen. The colon bacillus shows a gas formation of 1/3 hydrogen. Of course the total volume of gas is recorded before the sodic hydrate is added. 1,^ ^^-^ I 0. 0 o Fig. 40.—Colon bacillus. This microbe is quite large, in the comparative sense, and is morphologically typical of the group bacillus. The flagellae are few in number and comparatively long. • The gas formula with a positive indol reaction is practically conclusive as far as the presence of the colon bacillus is concerned. Add to this the other tests and we have presumptive evidence of sewage contamination, and any article of food or drink showing such contamination is unfit for human consumption. The colon bacillus, the bacilli of the hog cholera group and others have the power of reducing neutral red; producing a greenish-yellow fluorescence. For this reaction use glucose bouillon to which has been added I per cent, of a per cent, solution of neutral red. In examining milk, the pus cell and leucocyte count is considered imp
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