BACTERIOLOGICAL EXAMINATION OF SOIL 435 



which can be closed up by turning a handle, or opened by 

 turning in the opposite direction. The borer is pushed 

 down to the necessary depth ; the handle is then turned, 

 with the result that the earth enters the cavity; the handle 

 is again turned, enclosing the sample of earth completely ; 

 the borer is then withdrawn. The soil can now be examined 

 by thoroughly mixing a very small quantity of the earth 

 with melted nutrient gelatine, which can then be poured on 

 a plate, or better, made into a roll culture by Esmarch's 

 method. Another method is to wash the soil with sterile 

 water, which is examined as usual by the plate method. 



28—2 



