The Soil 
1 1 
they cease to develop or to do their work. 1 his can 
be remedied by an application of lime, in the proportion 
of 15 to 20 lb. of quicklime to a pole of ground, or 
three times that quantity if chalk is used instead of lime. 
These substances are alkaline, and neutralize the acidity 
of the soil. 
The time of greatest activity of these organisms in 
the soil is in spring and early summer, and then again 
in autumn. During these periods the soil is sufficiently 
warm, and there is enough moisture to allow them to 
move about freely. This, of course, coincides with the 
time of the greatest growth of plants, showing how wisely 
nature regulates everything for mutual advantage. 
The soil, however, is also tenanted by a greater or 
less proportion of bacteria which may cause diseases such 
as lockjaw ( Bacillus tetanus ), &c., and every care should 
be taken of wounds received when working in the soil. 
If wounds are already on the hands, no soil whatever 
should be allowed to get into the wounds. As a general 
rule, healthy persons can withstand even severe cuts when 
working in the soil, but this should not cause us to relax 
our watchfulness with regard to cleanliness in working. 
It is difficult for one to realize such infinitely small 
objects as these bacteria in the soil. A microscope of a 
high power should therefore be used. A little of the soil 
to be examined should be mixed with sterilized water. 
The smallest quantity of this water should then be put 
on a glass slide, covering it with a cover-slip. Great 
care must be taken to ensure that slide and cover-slip 
are perfectly clean. When the slide is placed under the 
microscope, large numbers of bacteria will be seen moving 
