To tube No. 1 add 1 c.c. liquefied butter. 2 add 0.5 c.c. liquefied butter. 3 add 0.3 c.c. liquefied butter. 4 add 0.2 c.c. liquefied butter. 5 add 0.1 c.c. liquefied butter. 6 add 0.05 c.c. liquefied butter. 7 add 0.03 c.c. liquefied butter. 8 add 0.02 c.c. liquefied butter. 9 add 0.01 c.c. liquefied butter. 5. Pour a plate cultivation from each of the gelatine-agar tubes and incubate at 28° C. 6. "Count" the plates after three days' incubation, and from the figures thus obtained estimate the number of organisms present per cubic centimetre of the sample. ~Qualitative.~-- _Apparatus Required_: Sterile beaker, its mouth plugged with sterile cotton-wool. Counterpoise for beaker. Scales and weights. Sterilised spatula. Water-bath regulated at 42° C. Separatory funnel, 250 c.c. capacity, its delivery tube protected against contamination by passing it through a cotton-wool plug into the interior of a small Erlenmeyer flask which serves to support the funnel. This piece of apparatus is sterilised _en masse_ in the hot-air oven. Large centrifugal machine. Sterile tubes (for the centrifuge) closed with solid rubber stoppers. Case of sterile pipettes, 10 c.c. Case of sterile graduated pipettes, 1 c.c. (in tenths of a cubic centimetre). METHOD.-- 1. Weigh out 100 grammes of the sample in a sterile beaker. 2. Plug the mouth of the beaker with sterile cotton-wool and immerse the beaker in a water-bath at 42° C. until the contents are completely liquefied. 3. Fill the liquefied butter into the sterile separatory funnel. 4. Transfer the funnel to the incubator at 37° C. and allow it to remain there for four days. At the end of this time the contents of the funnel will have separated into two distinct strata. (a) A superficial oily layer, practically free from bacteria. (b) A deep watery layer, turbid and cloudy from the growth of bacteria. 5. Draw off the subnatant turbid layer into sterile centrifugal tubes, previously warned to about 42° C., and centrifugalise at once. 6. Pipette off the supernatant fluid and fill the tubes with sterile 1 per cent. sodium carbonate solution previously warmed slightly; stopper the tubes and shake vigourously for a few minutes. 7. Centrifugalise again. 8. Pipette off the supernatant fluid; filling the tubes with warm sterile bouillon, shake well, and again centrifugalise, to wash the deposit. 9. Pipette off the supernatant fluid. 10. Prepare cover-slip preparations, fix and clear as for milk preparations, stain carbolic methylene-blue, Gram's method, Ziehl-Neelsen's method, and examine microscopically with a 1/12 inch oil-immersion lens. 11. Proceed with the examination of the deposit as in the case of milk deposit (see pages 450 _et seq._). EXAMINATION OF UNSOUND MEATS.