RY R. GREIG-SMITH. 



241 



does, so large a proportion of fat and slime in relation to its organic 

 matter, should only permit the passage of water with difficulty. 



In my experiments with soils, the action of the agricere was 

 demonstrated by treating the soil with a volatile disinfectant, 

 such as chloroform, and after the evaporation of the solvent, the 

 layers of soil were tested for their capacity of producing bacterial 

 growth. As the chloi'oform kills off all the protozoa, this dis- 

 turbing possible factor is removed, and the influence of the chlo- 

 roform in translating the agricere is shown by the nutritive 

 powers of the layers of soil being different. The upper layeis 

 contain the bulk of the agricere, deposited there by the evaporat- 

 ing solvent. The agricere, however, is deposited upon the 

 particles irregularly; there is not the uniform distribution which 

 obtained previous tu the addition of the solvent. Still, there is 

 more of the impervious agricere in the upper layers than in tin; 

 lower, and, as a result, the upper layers are less actively nutritive, 

 and the bacteria grow more quickly in the lower. This method 

 was used in testing the sewage-sick soil. 



The air-dried, sewage-sick soil was wetted with chloroform, and 

 after all odour had passed off, the la^^ers were carefully separated. 

 Ten grams of each were placed in small wide-mouthed bottles, and 

 moistened with i c.c. of sterile water, which was carefully stirred 

 into the soil with a stiff wire. The adhering soil was removed 

 with a small tuft of sterile cotton- wool, which was dropped into 

 the bottle. The soils were incubated for eight days at 28°, 

 evaporation being minimised by the bottles being covered ^\ ith a 

 bell- jar. 



Soil after evaporation of the chloroform. 



Soil-bacLeria in OOOOlj 

 8 days at 28". 



ifte 



19,600 

 29,400 

 28,200 

 29,600 

 35,400 

 .S9,(I00 



The greater growth of the soil-bacteria in the lower, as com- 

 pared with the top layers, is a confirmation of the view that the 



