_Fraenkel's Earth Borer._--This instrument consists of a stout hard-steel rod, 150 cm. long, marked in centimetres from the drill-pointed extremity. It is provided with a cross handle (adjustable at any point along the length of the rod by means of a screw nut). The terminal centimeters are thicker than the remainder of the rod, and on one side a vertical cavity about 0.5 cm. deep is cut. This is covered by a flanged sleeve so long as the borer is driven into the soil clockwise, and is opened for the reception of the sample of soil, when the required depth is reached, by reversing the screwing motion, and again closed before withdrawal of the borer from the earth by resuming the original direction of twist. It can be sterilised in a manner similar to that adopted for the scoop, or by repeatedly filling the cavity with ether and burning it off. ~Quantitative.~--Four distinct investigations are included in the complete quantitative bacteriological examination of the soil: 1. The enumeration of the aerobic organisms. 2. The enumeration of the spores of aerobes. 3. The enumeration of the anaerobic organisms (including the facultative anaerobes). 4. The enumeration of the spores of anaerobes. Further, by a combination of the results of the first and second, and of the third and fourth of these, the ratio of spores to vegetative forms is obtained. _Apparatus Required_: Case of sterile capsules (25 c.c. capacity). 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). Flask containing 250 c.c. sterile bouillon. Tall cylinder containing 2 per cent. lysol solution. Plate-levelling stand. 12 sterile plates. Tubes of nutrient gelatine. Tubes of wort gelatine. Tubes of nutrient agar. Tubes of glucose formate gelatine. Tubes of glucose formate agar. Water-bath regulated at 42° C. Bunsen burner. Grease pencil. Sterile mortar and pestle (agate). Sterile wide-mouthed Erlenmeyer flask (500 c.c. capacity). Sterile metal funnel with short wide bore delivery tube to just fit mouth of flask. Solid rubber stopper to fit the flask (sterilised by boiling). Pair of scales. Counterpoise (Fig. 107). Sterile metal (nickel) spoon or spatula. Fractional steriliser (Fig. 140). METHOD.-- 1. Arrange four sterile capsules numbered I, II, III, and IV; pipette 9 c.c. sterile bouillon into the first capsule, and 9.9 c.c. into each of the remaining three. 2. Pipette 100 c.c. sterile bouillon into the Erlenmeyer flask. 3. Remove the cotton-wool plug from the flask and replace it by the sterile funnel. 4. Place flask and funnel on one pan of the scales, and counterpoise accurately. 5. Empty the sample of soil into the mortar and triturate thoroughly.