BY R. GRKIG-SMITH. 



685 



bottom of a moist chamber), and, in this, the soil showed a 

 depth of two inches. The soil was then thorougiily wetted by 

 sprinkUng from above with distilled water, and allowed to dry in 

 the air. The top half was separated from the lower, and both por- 

 tions were exposed to the air for a day. Suspensions of Bac. 

 piodigiosns were added to the soil and to its extract, as in 

 previous experiments. 



EXPKRIMKNT V. 



The greater toxic power of the bottom soil appears to show 

 that the toxin is carried down by the water percolating from 

 above. 



Treatment of the Soil with Non-Volatile Disinfectants. — 

 If the action of the volatile disinfectants is solely to kill phago- 

 cytic protozoa, the non-volatile disinfectants should behave 

 in a precisely similar manner, while the fatty bodies in the 

 soil should be unaffected. To test if this reasoning was good, 

 portions of a soil were treated with solutions of 5 /' phenol, 

 0-1 % mercuric chloride, 1 % potassium bichromate, and 1 % 

 copper sulphate, for a day. They were then washed and 

 dried. A portion of each was treated with chloroform, and com- 

 pared with the untreated portion. Unfortunately all the 

 portions were toxic, and the whole of the added bacteria were 

 killed off. Evidently the non-volatile disinfectant adheres 

 tenaciously to the soil-particles, and resists removal by a 

 moderate quantity of water. Upon again moistening the 

 soil, the residual disinfectant is dissolved, and checks bac- 



