Gelatine streak. Agar streak. Potato. Nutrient broth. Litmus milk. Dextrose peptone solution. Lævulose peptone solution. Galactose peptone solution. Maltose peptone solution. Lactose peptone solution. Saccharose peptone solution. Raffinose peptone solution. Dulcite peptone solution. Mannite peptone solution. Glycerin peptone solution. Inulin peptone solution. Dextrin peptone solution. 17. Differentiate the bacilli after isolation by means of their cultural reactions and biological characters into members of: I. The Escherich Group. B. coli communis. B. coli communior. B. lactis aerogenes. B. cloacæ. II. The Gærtner Group. Bacillus enteritidis (of Gærtner). B. paratyphosus A. B. paratyphosus B. Bacillus choleræ suum. III. The Eberth Group. B. typhosus. B. dysenteriæ (Shiga). B. dysenteriæ (Flexner). B. fæcalis alcaligines. 18. Confirm these results by testing the organisms isolated against specific agglutinating sera obtained from experimentally inoculated animals. If a positive result is obtained when using this method, it only needs a simple calculation to determine the smallest quantity (down to 0.1 c.c.) of the sample that contains at least one of the microbes of indication. For instance, if growth occurs in all the tubes from 4 to 10, and that growth is subsequently proved to be due to the multiplication of B. coli, then it follows that at least one colon bacillus is present in every 10 c.c. of the water sample, but not in every 5 c.c. If, on the other hand, the presence of the B. coli can only be proved in flask No. 7, then the average number of colon bacilli present in the sample is at least one in every 50 c.c. (i. e., twenty per litre), but not one in every 25 c.c. and so on. The general outline of the method of identifying the members of the coli-typhoid group is given in the form of an analytical schema--whilst the full differential details are set out in tabular form. ANALYTICAL SCHEME FOR ISOLATION OF MEMBERS OF THE COLI AND TYPHOID GROUPS.