TECHNIC BACTERIOLOGICAL EXAMINATION OF SOILS. 279 



mark the weight on the bottle and sterilize in the same manner as the other 

 bottles. 



Weigh each of the 30 jell glasses to the nearest decigram and record the 

 weight on the tin lid. As a rule it is advisable to sterilize the jell glasses wtli 

 dry heat so as to be sure that they are free from anj^ contaminations resulting 

 from previous use or storage. 



Plug the stems of the 10 cc. the o ec. and the 1 cc. pipettes with absorbent 

 cotton. Prepare 12 inch by 1 inch test tubes by placing a mat of absorbent 

 cotton in the bottom of each. Place the pipettes in the test tubes, plug the 

 test tubes with cotton and sterilize in a hot air sterilizer. (Two ten cc. or 

 four one cc. pipettes are sterilized in one test tube.) 



Plate I. 

 Ready to Start. 



Media is made up and sterilized and distiUed water for making dilutions 

 is sterilized in the special boiler. The casein solution for ammonification, the 

 mannite solution for nitrogen fixation and the ammonium sulphate solution 

 for nitrification are made up and sterilized. 



The light wooden mallet, a bunsen burner, the two quart saucepan, the 

 aluminum spoon, the sixteen ounce salt mouth bottles, the weighed bottles 

 and jell glasses, the ten one pint mason jars and the balance are arranged on 

 the laboratory table. (Plate I.) The heavy mallet, the driving head, and the 

 samples are taken to the field and the soil samples taken according to direc- 

 tions given in a previous article.- Eleven rubber stoppers of such size that 

 they will fit the twelve ounce bottles are put m the inner part of a double 



