SOIL 473 



metres from the drill-pointed extremity. It is pro- 

 vided 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 .-r-Four distinct investigations are in- 

 cluded in the complete quantitative bacteriological 

 examination of the soil : 



i. The enumeration of the aerobic organisms. 



2.' The enumeration of the spores of aerobes. 



3. The enumeration of the anaerobic organisms (in- 

 cluding 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, i 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. 



