House and Garden 
PARASITIC BACTERIA WHICH ATTACK LIVING TISSUES 
bined use of which satisfactory results are obtained. 
Inasmuch, however, as all methods of sewage treat¬ 
ment depend upon, or are preliminary to, bacterial 
action, it is of interest to consider first the natural 
laws governing these life processes, without which 
all efforts at sewage purification would be futile. 
Let it be clearly understood that to change organic 
matter into harmless compounds, it must be burned. 
Therefore, to burn by fire or oxidation, is the only 
practical way of destroying filth. A simple example 
is afforded by impurities in our blood, which in the 
presence of air are oxidized or burned up in the lungs, 
from which we exhale, in the form of carbonic acid 
gas, the products of combustion. Kitchen refuse in 
cities is burned at garbage works, and in the country 
districts much is destroyed by being fed to pigs and 
poultry, while the remainder is turned into manure 
and feeds the land, the top soil of which contains 
countless millions of lower organisms. 
It is all changed by fast or slow oxidation. The 
same law applies to the excretions of men and ani¬ 
mals. These always contain aerobic or oxidizing 
bacteria, as well as those organisms which prepare 
sewage for being oxidized. It is not uncommon for 
a single gallon of sewage water, of which i-ioooth 
part only is polluting matter, to contain 24,802,000, 
000 of these little scavengers. This is approxi¬ 
mately the number per gallon in the sewage of the 
city of London. 
Here then indeed, is a force provided by nature, 
of immeasurable service. Were it to cease, all forms 
of life would quickly become extinct. The number 
of the known varieties of health preserving bacteria 
is upward of four hundred, or ten times that of the 
pathogenic or disease producing species, which mi¬ 
nority is fortunately to a greater or lesser degree 
“crowded out” of existence by the vastly superior 
numbers of health protecting antagonists. The rel¬ 
ative numbers of these two classes of bacteria have 
frequently been compared to the proportion that 
law abiding citizens bear to criminals in a com¬ 
munity. The laws which govern the action of bac¬ 
teria are not as dissimilar from those under which 
mankind exists as might be supposed. To the 
greater majority, air, moisture and food are requi¬ 
sites. Many varieties of these minute agents may be 
cultivated for the special purpose of sewage purifi¬ 
cation. That is to say, suitable environment and 
control will assist their life purposes. What are 
these life purposes ? A generation has not passed 
since it was believed that sewage purified in soil, 
underwent changes, due entirely to chemical action. 
Now it is well established that these changes are 
the result of bacteria, a low form of vegetable life. 
I he majority of those indigenous to sewage, belong 
to that class which are most active in the presence 
of air, and are known as “aerohes,” the minority 
are known as “anaerobes,” living without air. Of 
this latter class, a small number are “obligate an¬ 
aerobes,” which not only do not require oxygen, 
but may actually be inhibited or even killed by its 
presence, but the greater number are “facultative 
anaerobes,” and can live either with or without oxy¬ 
gen. This is fortunate, seeing that sewage water 
may at one time contain little or no oxygen, while 
at another may be well oxygenated. The products 
also of bacteria, known as “enzymes,” not only 
possess immense power in breaking up organic com¬ 
pounds, but enable a bacillus to act at a considerable 
distance, as well as in its immediate neighborhood. 
These then, are the agents with which we must live 
in friendly relationship, if our highly civilized com¬ 
munities are not to be decimated by disease. It 
cannot be expected that the neglect of an army of 
such useful bacteria can take place with impunity. 
Food must not be lacking, and for the greater num¬ 
ber of varieties, air is equally necessary. Although 
differences of opinion exist, it seems to be generally 
conceded that preliminary to the process of oxidi¬ 
zing sewage, it is wise to collect and retain it, not in 
ordinary cesspools, which are a menace to health, 
but in correctly designed and properly managed 
water tight reservoirs, known as “septic” or “reso¬ 
lution” tanks, because, (1) they avoid the deposit 
of solid matters at the entrance to passages leading 
downwards from the surface of the ground or other 
filtering material in which the sewage is purified; 
for, although in volume this solid matter is less than 
i-ioooth part that of the sewage water, it is sufficient 
to quickly interfere with the all important aeration of 
the interstices or spaces, in which the presence of 
air is a sine qua non, and which otherwise can only 
be insured by continual manual labor in raking the 
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