TECHNIC BACTERIOLOGICAL EXAMINATION OF SOILS. 301 



are later on put in the bottles for silt and clay are found to work up around 

 the stoppers and cause them to stick unduly. (This holds true even when 

 the proper stoppers are kept with the bottles they are made for.) 



Summary. 



(1) All apparatus used should be sterile. 



(2) Fresh samples of soil are used for analysis. 



(3) A 50 gram aliquot of fresh soil has been found as satisfactory as a 

 100 gram aliquot. 50 grams of fresh soil is recommended as the standard 

 amount of soil to take. 



(4) Dilutions are made of the bacteria and not of the soil. 



(5) Fifty grams of fresh soil and 200 cc of sterile water are used as the 

 basis of all dilutions. 



(6) Each higher bacterial dilution should be made by taking 10 cc of 

 the lower bacterial dilution and 90 cc of sterile water. 



(7) Water should be added to dilution bottles after the water and 

 bottles have been sterilized. 



(8) Bacterial dilutions should be shaken long enough so that variations 

 in carrying out the teehnic of shaking will be eliminated. 



(9) A one cc aliquot of the proper dilution is used for plating. This is 

 added direct to the petri dish. 



(10) The procedures followed in preparing the apparatus, in mixing the 

 soil sample, in making the liacterial dilutions, and in plating are given in 

 detail. 



References 



^Special Committee appointed by Society of American Bacteriologists, 

 at Philadelphia meeting, December, 1914. 



-Noyes, H. A., Journal of American Society of Agi'onomy. Volume 

 7, No. 5. 



^Brew, J. D., Paper on Use of 0.01 cc pipettes in Milk Analysis. 



Breed, Rob. S. and Brew, J. D., New York Agricultural Experiment 

 Station, Technical Bulletin No. 49. 



^Brown, P. E., Iowa Experiment Station Research Bulletin No. 11. 

 page 399. 



^Conn, H. Joel, New York Agricultural Experiment Station, Technical 

 Bulletin No. 35, page 9. 



''Conn, W. H., Reprint 295 from the Public Health Reports, August. 1915. 



8432 — 20 



