BY R. GREIG-SMITH. 725 



tozoa to soil do not bring about a diminution of the bacteria. I 

 have suggested that the bacteria in raw soils limit themselves by 

 the toxic action of their own products of decomposition. Fred 

 thinks the altei-ation in treated soils is caused by a stimulation 

 of the bacteria by the disinfectant. That the nature of the 

 surviving bacteria may partly explain the rise in bacterial num- 

 bers, was shown by an experiment of Russell and Hutchinson, 

 who found that a soil capable of supporting a definite number of 

 bacteria, could accommodate a further number of foreign bacteria. 



One of the undoubted effects of the treatment by volatile dis- 

 infectants is, that the soil becomes more nutritive. Russell and 

 others have shown that there is an instantaneous production of a 

 small quantity of ammonia. I have suggested that the nutrients 

 are made more available by the translocation of the agricere or 

 fatty substances of the soil, and have shown that the portions of 

 soil, where the agricere gathers, are less nutritive than the other 

 portions. Buddin noted that a disinfectant, such as pyridine, 

 can be attacked and utilised by bacteria. Hutchinson and 

 MacLennan ascribed the growth of bacteria in soils partially 

 sterilised by lime to the chemical action of the lime upon the 

 organic matter of the soil. A number of writers, Stormer, 

 Heinze, Loew and Aso, consider that the treatment brings about 

 a change in the availability of the nitrogen of the soil. 



The action of a volatile disinfectant appears to be similar to 

 the simple drying of the soil, although the effect of the disin- 

 fectant is more exaggerated. Buddin writes— "It is possible to 

 trace a certain relationship between the action of all the sub- 

 stances used. The intensity of the effects shades off' gradually 

 from that of the powerful non-volatile antiseptics through cresol 

 and formaldehyde to the more and less potent volatile antiseptics 

 respectively, till finally the action -of merely spreading out the 

 soil in a thin layer is reached." 



While the effect of air-drying rapidly wears off, that of the 

 disinfectant persists for some time. The effect of the increased 

 soil-activity, which is intimately associated with the growth of 

 micro-organisms, does not appear to be due to an alteration of 



