SOIL 475 



10. In like manner add o.i c.c. of the contents of 

 capsule II to capsule III, and then o.i c.c. of the 

 contents of capsule III to capsule IV. 



Then i c.c. fluid from capsule I contains soil water from .01 gm. 



earth. 

 Then i c.c. fluid from capsule II contains soil water from .0001 



gm. earth. 

 Then i c.c. fluid from capsule III contains soil water from 



.000001 gm. earth. 

 Then i c.c. fluid from capsule IV contains soil water from 



.0000000 1 gm. earth. 



(A) Aerobes (Vegetative Forms and Spores). 



11. Pour a set of gelatine plates from the contents 

 of each capsule two plates in a set, and containing 

 respectively o.i c.c. and 0.4 c.c. of the diluted soil 

 water. Label and incubate. 



12. Pour similar sets of wort gelatine plates from 

 the contents of capsules II and III, label, and incubate 

 at 20 C. 



13. Pour similar sets of agar plates from the contents 

 of capsules II and III; label and incubate at 37 C. 



14. Weigh out a second sample of soil 10 grammes 

 dry over a water-bath until of constant weight and 

 calculate the ratio 



wet soil weight 

 dry soil weight 



15. " Count" the plates after incubation for three, 

 four, or five days, and correcting the figures thus ob- 

 tained by means of the "wet" to "dry" soil ratio 

 estimate 



(a) The number of aerobic micro-organisms present 

 per gramme of the soil. 



(b) The number of yeasts and moulds present per 

 gramme of the soil. 



(c) The number of aerobic organisms "growing at 

 37 C." present per gramme of the soil. 



