122 STERILIZATION AND DISINFECTION 
bacteria, the oxidation processes would be limited by the solubility 
of the oxygen in water. According to Winkler (1889) this is 10.14 
parts per million at 15° C. and 760 inm. 
Incineration. As a means of sterilization, this method needs no 
discussion. It is plainly a process of oxidation and very efficient. 
Small incinerators may be purchased which will handle practically all 
ordinary material. 
Flaming. This simple method is a serviceable one for the bac- 
teriologist. Platinum wires may be sterilized by this method. Watch 
glasses, slides, etc., may be completely sterilized if a little care is used 
during the flaming process. The Bunsen burner or alcohol lamp may 
furnish the heat. 
Hot-air Oven. The apparatus for this method is constructed much 
like the ordinary baking oven. Quite often an attempt is made to 
insulate it either by means of a double wall or some special material. 
The temperature is usually maintained by means of a gas flame or 
electricity. Some hot-air sterilizers are so well insulated that after 
the temperature has been raised to 180° C., this temperature is main- 
tained for a long time even though the source of heat is removed. The 
hot-air oven is used for sterilizing all dry glassware. This should 
be put into the sterilizer when it is cool and gradually raised to the 
sterilization temperature. A temperature of 180° C. for from one hour 
to one hour and a half will suffice for all ordinary apparatus. This 
method has definite limitations and should not be applicd to the sterili- 
zation of media, thick glassware, etc, 
Moist Hrat 
The theory of sterilization by moist heat has been studied by 
Chick (1910). Here three essentially different processes take place: 
1. Direct effect of heat on bacterial protein. 
2. Effect of water possibly hydrolytic on these proteins at high 
temperature. 
3. Desiccation of bacteria. 
It was pointed out by Miss Chick that an analogy exists between 
the disinfection of bacteria by hot water and the “ heat coagulation ”’ 
of proteins. This may help to account for the difficulty with which 
spores are disinfected by hot water when compared with the vegetative 
cells. The protein in the spores may be more resistant to hydrolysis 
than that in vegetative cells. Both changes follow the monomolecular 
law and both are greatly increased by the presence of minute amounts 
