(INCLUDING TINNED OR POTTED MEATS, FISH, ETC.) The bacterioscopic examination of unsound food is chiefly directed to the detection of those members of the Coli-typhoid group--B. enteritidis of Gaertner and its allies--which are usually associated with epidemic outbreaks of food poisoning, and such anaerobic bacteria as initiate putrefactive changes in the food which result in the formation of poisonous ptomaines, consequently the quantitative examination pure and simple is frequently omitted. A. Cultural Examination. Quantitative.-- _Apparatus Required_: Sterilised tin opener, (if necessary.) Erlenmeyer flask (500 c.c. capacity) containing 200 c.c. sterile bouillon and fitted with solid rubber stopper. Counterpoise. Scissors and forceps. Scales and weights. Water steriliser. Hypodermic syringe. Syringe with intragastric tube. Rat forceps. Case of sterile capsules. Filtering apparatus as for water analysis. Case of sterile plates. Case of sterile graduated pipettes, 10 c.c. (in tenths of a cubic centimetre). Case of sterile graduated pipettes, 1 c.c. (in tenths of a cubic centimetre). Plate-levelling stand. Tubes of nutrient gelatine. Tubes of nutrient agar. Water-bath regulated at 42° C. Bulloch's apparatus. METHOD.-- 1. Place the flask containing 200 c.c. sterile broth on one pan of the scales and counterpoise accurately. 2. Mince a portion of the sample by the aid of sterile scissors and forceps, and add the minced sample to the bouillon in the flask to the extent of 20 grammes. 3. Make an extract by standing the flask in the incubator running at 42° C. (or in a water-bath regulated to that temperature) for half an hour, shaking its contents from time to time. Better results are obtained if an electrical shaker is fitted inside the incubator and the flask kept in motion throughout the entire thirty minutes. Now every centimetre contains the bacteria washed out from 0.1 gramme of the original food. 4. Inoculate tubes of liquefied gelatine as follows: To tube No. 1 add 1.0 c.c. of the extract. 2 add 0.5 c.c. of the extract. 3 add 0.3 c.c. of the extract. 4 add 0.2 c.c. of the extract. 5 add 0.1 c.c. of the extract. Pour plates from these tubes and incubate at 20° C. 5. Prepare a precisely similar set of agar plates and incubate at 37° C. 6. Pipette 5 c.c. of the extract into a sterile tube, heat in the differential steriliser at 80° C. for ten minutes. 7. From the heated extract prepare duplicate sets of agar and gelatine plates and incubate anaerobically in Bulloch's apparatus at 37° C. and 20° C. respectively.