484 
The farmer long before this, also, had realized the value of what 
is known as “ fallowing/’ in which sufficient food is allowed to ac- 
cumulate for a period, to supply the bacterium with its food. 
From the fact, however, that these discoveries do not absolutely 
explain or account for all the problems of soil fertility or lack of 
fertility, we realize that these bacteria are merely another determining 
factor in connection with the problem. 
These results have remained without intrinsic alteration till quite 
recently, when we are brought in contact with another phase of the 
question, the elucidation of which has been solved by Russell and 
1 lutchinson within the last year, viz., the partial sterilization of soil 
as a means to increase its fertility. 
Here again we have the accumulated experience of ages of agri- 
cultural practice explained by the results of scientific investigation. 
The effect of heat on soils has been known not only in European 
agricultural practice but in other countries — notably India and I find 
too that it is known to Javanese gardeners in this country, whose 
common practice is to bum together a mixture of earth and dry 
manure before using it in pots for horticultural purposes. When 
asked why they practice this method — they reply that it is valuable* 
although they offer no reason why this is so. 
It is now known that partial sterilization of soils, not only by 
heat, but by certain antiseptics such as chloroform and carbon 
bisulphide, has a very beneficial action, and the reason for this action 
has been most ably explained by the above mentioned investigators. 
Crops grown on soils sterilized by heat become doubled in some 
cases, and almost equally good results are obtained by treating with 
antiseptics. The plants on analysis are also found to contain much 
more nitrogen than those from undertreated soils, showing that the 
result of the treatment has effected an increase of nutriment. 
Russell and Hutchinson found that (1) the nitrogen combined as 
ammonia in the soil increased remarkably under the treatment (2) the 
treatment did not effect complete sterilization (3) the bacteria in the 
soil were greatly reduced in number at first (4) subsequently the bac- 
teria increased to an enormous extent, and far beyond the original 
number, (5) the nitrifying bacteria were destroyed. 
From these results they naturally concluded that the increased 
ammonia content of soil treated in this manner was due to the increase 
in bacteria, and the absence of nitrifying bacteria which enabled the 
ammonia to accumulate ; but the real value and brilliancy of their 
discoveries was the realization that the subsequent enormous increase 
of the bacteria was due to the absence of some factor in the soil which 
had been destroyed in the process of partial sterilization. 
