21. Calculate the ratio existing between spores and spores + vegetative forms under each of the two groups, aerobic and anaerobic micro-organisms. ~Qualitative Examination.~--The qualitative examination of soil is usually directed to the detection of one or more of the following: Members of the Coli-typhoid group. Streptococci. Bacillus anthracis. Bacillus tetani. Bacillus oedematis maligni. The nitrous organisms. The nitric organisms. 1. Transfer the remainder of the soil water (88 c.c.) to a sterile Erlenmeyer flask by means of a sterile syphon. 2. Fix up the filtering apparatus as for the qualitative examination of water, and filter the soil water. 3. Suspend the bacterial residue in 5 c.c. sterile bouillon (technique similar to that described for the water sample, _vide_ pages 434-436). Every cubic centimetre of suspension now contains the soil water from nearly 1 gramme of earth. The methods up to this point are identical no matter which organism or group of organisms it is desired to isolate; but from this stage onward the process is varied slightly for each particular bacterium. ~I. The Coli-typhoid Group.~-- ~II. Streptococci.~-- ~III. Bacillus Anthracis.~-- ~IV. Bacillus Tetani.~-- The methods adopted for the isolation of these organisms are identical with those already described under water (page 437 _et seq._). ~V. Bacillus Oedematis Maligni.~--Method precisely similar to that employed for the B. tetani. ~VI. The Nitrous Organisms.~-- 1. Take ten tubes of Winogradsky's solution No I (_vide_ page 198) and number them consecutively from 1 to 10. 2. Inoculate each tube with varying quantities of the material as follows: To tube No. 1 add 1.0 c.c. of the soil water. To tube No. 2 add 0.1 c.c. of the soil water. To tube No. 3 add 1.0 c.c. from Capsule I. To tube No. 4 add 0.1 c.c. from Capsule I. To tube No. 5 add 1.0 c.c. from Capsule II. To tube No. 6 add 0.1 c.c. from Capsule II. To tube No. 7 add 1.0 c.c. from Capsule III. To tube No. 8 add 0.1 c.c. from Capsule III. To tube No. 9 add 1.0 c.c. from Capsule IV. To tube No. 10 add 0.1 c.c. from Capsule IV. Label and incubate at 30° C. ~VII. The Nitric Organisms.~-- 3. Take ten tubes of Winogradsky's solution No II, number them consecutively from 1 to 10 and inoculate with quantities of soil water similar to those enumerated in section VI step 2. Label and incubate at 30° C. 4. Examine after twenty-four and forty-eight hours' incubation. From those tubes that show signs of growth make subcultivations in fresh tubes of the same medium and incubate at 30° C. 5. Make further subcultivations from such of those tubes as show growth, and again incubate. 6. If growth occurs in these subcultures, make surface smears on plates of Winogradsky's silicate jelly (_vide_ page 198). 7. Pick off such colonies as make their appearance and subcultivate in each of these two media. TESTING FILTERS.