Soil Changes Produced By Micro-organisms. 
5 
It will be impossible in an article of this kind to tell how they are 
measured, although the process is comparatively simple. The reader 
will have to take the writer’s word for it that it can be done and 
with a remarkable degree of accuracy. Some of the cocci or spher¬ 
ical forms are so small that it has been estimated that one billion 
could easily be contained in a drop of water having a volume of 
about one fortieth of a teaspoonful. With many of the rods or 
bacilli, we should need fifteen to twenty thousand individuals placed 
end to end to make one inch. The largest bacteria, as a rule, are 
found among the spirilla. These vary in length from one twelve 
thousandth to one six hundred twenty-fifth of an inch and from 
one fifty thousandth to one seven thousandth of an inch in diameter, 
while the bacilli average around one fifteen thousandth of an inch 
long by one thirty thousandth of an inch in diameter. 
Although extremely small, bacteria make up for this deficienc 
by their tremendous numbers, through which agency they are cap¬ 
able of accomplishing wonderful results, both as friends and foes, 
in a remarkably short time. Multiplication takes place, by a process 
called fission, once about every twenty minutes to a half hour and 
proceeds by a geometrical progression. Thus, if we have a single 
living germ at the present moment, it will increase in size, and at 
the end of twenty minutes, will divide in the middle by the forma¬ 
tion of a cross partition (fission), and each half will become a com¬ 
plete organism in itself. We thus have two germs; these two again 
divide by the same process so that after twenty minutes more, there 
are four and then eight, sixteen, thirty-two, sixty-four, etc. If 
there were no forces to check this growth, it would be difficult, 
indeed, to predict just what would become of the rest of us here 
upon the earth; but, fortunately, multiplication is controlled by the 
excretions of the germs themselves. It has been estimated that if 
division took place once every twenty minutes, and that it pro¬ 
ceeded at this rate uninterrupted for twenty-four hours, the de¬ 
scendants of one germ would number 1,806,655,286,826,042,269,- 
696, or, in round numbers, 1,800,000 trillions. Considering that 
each organism was one fifteen thousandth of an inch long, the 
above number, if placed end to end, would make a string nearly 
two trillion miles long; it would reach to the sun and back again 
10,000 times, would go around the earth’s equator 70,000,000 times, 
and it would take a ray of light 100,000 years to pass from one end 
of it to the other. 
The parent cell and all of its descendants constitute a bacterial 
colony, and when the microorganism is grown on a suitable food 
