106 PA THOGENIC BA CTERIA. 



The Sterilization and Protection of Instruments 

 and Glassware Used in Experimentation. Steriliza- 

 tion may be accomplished by either moist or dry heat. 

 For the perfect sterilization of objects capable of with- 

 standing it dry heat is preferable, because more certain 

 in its action. If we knew just what organisms we had 

 to deal with, we might be able in many cases to save 

 time and gas, but while some simple non-spore-producing 

 forms are killed at a temperature of 60 C., others can 

 withstand boiling for an hour ; it is therefore best to 

 employ a temperature high enough to kill all with cer- 

 tainty. Platinum wires used for inoculation are held in 

 the direct flame until they become incandescent. In 

 sterilizing such wires attention must be bestowed upon 

 the glass handle, which should be held in the flame for 

 at least half its length for a few moments when used for 

 the first time each day. Carelessness in this respect may 

 cause the loss of much time by contaminating cultures. 



Knives, scissors, and forceps may be exposed for a very 

 brief time to the direct flame, but this affects the temper 

 of the steel when continued too long. They may also 

 be boiled, steamed, or carbolized. 



All glassware is sterilized by exposure to a sufficiently 

 hijLjh temperature, 150 C. or 302 F., for one hour in the 

 well-known hot-air closet (Fig. 9). A temperature of 

 150 C. is sufficient to kill all known bacteria and their 

 spores if continued for an hour. 



Rubber stoppers, corks, wooden apparatus, and other 

 objects which are warped, cracked, charred, or melted 

 by so high a temperature must be sterilized by moist 

 heat in the steam apparatus for at least an hour before 

 they can be pronounced sterile. 



It must always be borne in mind that after sterilization 

 has been accomplished the same sources of contamination 

 that originally existed are still present, and begin to 

 operate as soon as the objects are removed from the 

 sU-rili/ini; apparatus. 



To Schroder and Van Dusch belong the credit of 



