THE MICROBES OF THE SOIL 



277 



To study the microbes present in soil, both solid 

 and liquid media are used, but the employment of 

 the former is much more satisfactory. The follow- 

 ing methods are used by bacteriologists to ascertain 

 the number of microbes in a known weight, etc., of 

 soil : (a) A sample of the dried soil is triturated with 

 sterilised distilled water, and then a small quantity 

 of this water is sprinkled on the surface of a gelatine 

 plate, (b) The soil is introduced into a test-tube 

 containing liquefied gelatine. After a thorough 

 shaking the mixture is poured out upon a glass 

 plate, so as to form a plate- cultivation, (c) When 

 bouillon is used the soil is first triturated with water, 

 and then a drop of the water is transferred to a 

 flask containing sterilised bouillon. 



Among the results obtained of the number of 

 microbes present in various soils are the following : 



(A) GRIFFITHS' ANALYSES. 



Samples of Soil from 



Number of 

 Microbes in 1 gram. 



Lincoln (Monk's Road), 



,, (Castle grounds), 

 Manchester (Infirmary grounds), . 



,, (Plymouth Grove), 

 London (Forest Gate), .... 

 ,, (Hyde Park), .... 

 Paris (Forest of Ville d'Avray), . 



(Near Sevres) 



,, (Pare Monceaux), 

 Dieppe (near Church of St. Jacques), . 



,, (near the Casino), 

 New Zealand (after 14 weeks' desiccation), 



611,000 



720,000 



1,230,000 



550,000 



430,000 



820,000 



780,000 



880,000 



754,000 



1,360,000 



1,200,000 



240,000 



