Fill a graduated cylinder with water to the 20 cc. mark, and then add the sample till the level of the mixture reaches the 30 cc. mark. Close the graduate, or pour the contents into an Erlenmeyer flask, and shake the mixture vigorously for 15 to 20 seconds. To facilitate thorough mixing the mixture should not fill more than three-fourths of the container in which the shaking is performed. For tomato sauce or pastes, or products running very high in the number of organisms, or of heavy consistency, 80 cc. of water should be used with 10 cc. or 10 grams of the sample. In the case of exceptionally thick or dry pastes, it may be necessary to make an even greater dilution. Pour the mixture into a beaker. Thoroughly clean the Thoma-Zeiss counting cell so as to give good Newton’s rings. Stir thoroughly the contents of the beaker with a scalpel or knife blade, and then, after allowing to stand 3 to 5 seconds, remove a small drop and place upon the central disk of the Thoma-Zeiss counting cell and cover immediately with the cover-glass, observing the same precautions in mounting the sample as given under 28.[8] Allow the slide to stand not less than 10 minutes before beginning to make the count. Make the count with a magnification of about 180 diameters to obtain which the following combination, or their equivalents, should be employed: 8 mm. Zeiss apochromatic objective with X6 Zeiss compensating ocular, or an 8 mm. Spencer apochromatic objective with X10 Spencer compensating ocular with draw-tube not extended. Count the number of yeasts and spores[9] on one-half of the ruled squares on the disk (this amounts to counting the number in 8 of the blocks, each of which contains 25 of the small ruled squares). The total number thus obtained equals the number of organisms in 1/60,000 cc. if a dilution of 1 part of the sample with 2 parts of water is used. If a dilution of 1 part of the sample with 8 parts of water is used the number must be multiplied by 3. In making the counts, the analyst should avoid counting an organism twice when it rests on a boundary line between two adjacent squares. [8] This number refers to the section as given in the Methods of Analysis of the Association of Agricultural Chemists. [9] Comment by authors: The organisms counted as “yeasts and spores” are the yeast cell and yeast and mold spores, not bacteria spores. Bacteria.—Tentative Estimate the number of rod-shaped bacteria from the mounted sample used in 29[10] (yeasts and spores), but before examination allow the sample to stand not less than 15 minutes after mounting. Employ a magnification of about 500, which may be obtained by the use of an 8 mm. Zeiss apochromatic objective with X18 Zeiss compensating ocular with draw-tube not extended, or an 8 mm. Spencer apochromatic objective with X20 Spencer compensating ocular and a tube length of 190, or their equivalents.[11]