SUMMARY 
ii 5 
It is fermentation of substances containing nitrogen 
—putrid fermentation. 
The products of these fermentative changes are 
gases which give odors; acids—lactic, acetic and bu¬ 
tyric ; weak alcohol, occasionally, and ptomaines 
which, when poisonous, are called toxines. 
When putrefaction has ended and the disagreeable 
products have disappeared, the residue is usually harm¬ 
less and inoffensive. If the processes of decomposition 
go on in an abundance of oxygen, decay is usually 
reached without offensive products. 
Sterilization is the removal of all life and is effected 
by steam, dry heat, chemicals, or filtration. 
To remove bacteria, air may be filtered through cot¬ 
ton wool and liquids through unglazed clay or similar 
substances. 
An antiseptic retards or prevents growth. A dis¬ 
infectant kills. 
Some substances are antiseptic or disinfectant ac¬ 
cording to their strength or the conditions under 
which they act. Sunshine is Nature’s free disin¬ 
fectant; light is commonly an antiseptic, and may be 
a disinfectant. Dryness, excess of moisture, salt, 
strong acids, the essential oils, soap, hot water, etc., 
may be antiseptic with some species and disinfectants 
with others. 
Pasteurization , chiefly applied to milk and cream, 
is a process for killing certain germs which cannot 
endure the temperature of 155 0 to 165° F. for twenty 
Decay 
