16 LABORATOKr BACTERIOLOGY. 



EXERCISE X. 



THE INFLUENCE OP DEXTROSE ON THE AMMONIFICATION OF 

 DRIED BLOOD AND COTTONSEED MEAL. 



1. "Weigh off twelve 100 gram portions of air-dry, sieved 

 soil, in tumblers. 

 3. Arrange thus : 



1 & 2 — ~> grams dried blood. 



3 & 4 — 5 grams dried blood + 1 gram dextrose. 

 5 & 6 — 5 grams dried blood + 3 grams dextrose. 

 7 & S — ."> grams cottonseed meal. 

 9 & 10 — .'i grams cottonseed meal + 1 gram dextrose. 

 11 & 12 — 5 grams cottonseed meal + 3 grams dextroSe. 



3. Stir thoroughly with a sterile spatula. 



4. To each add 10 cc. of a soil infusion prepared by shak- 

 ing 100 grams of a fresh sample of soil in 200 cc. of sterile 

 water for 5 minutes. 



5. Add sterile water to bring the moisture content up to 

 the optimum for the soil and then 18 cc. additional for the 

 nitrogenous materials. 



6. Cover and incubate 7-8 days at 20° C. 



7. Then determine the ammonia formed by transferring 

 and distilling in the usual way. 



