Laboratory Outline for General Bacteriology 



recommended for sterilizing platinum needles, spatulas, forceps, 

 etc. When sterilizing a needle heat the entire length of it to redness 

 in the flame. When sterilizing hold needle vertically in flame. Pass 

 the lower part of the handle three or four times through the flame. 



Before sterilization a platinum needle should be dried by hold- 

 ing it near the flame. This prevents sputtering which scatters 

 organisms, especially when materials such as fat and protein are 

 thrust into the flame. This drying is of special importance when 

 working with pathogenic material. 



Cool the sterilized needle before using. 



Do not let the sterilized needle touch anything except the cul- 

 ture from which the inoculation is being made and the medium to 

 be inoculated. 



Sterilize needle after using before laying it down. 



By passing instruments like forceps and spatulas several times 

 through a hot flame they may be sterilized. 



Sterilization by hot air. The usual method of sterilizing all 

 glassware, instruments with metal handles, etc., is by exposure to 

 hot air. A temperature of 160 C. should be maintained for one 

 hour. Heating and cooling is done slowly to avoid breaking the 

 glassware. 



Sterilization by steam. Under ten pounds pressure for fifteen 

 minutes in an autoclav all life is destroyed unless the material 

 is in large bulk. For flasks and larger volumes of liquid the period 

 of heating is prolonged to twenty minutes. The temperature thus 

 obtained is from 114 to 115 C. 



Steam without pressure at 100 C. is used. Materials are 

 heated for twenty to thirty minutes on three successive days. On 

 the first day the vegetative cells are killed. The spores remaining 

 develop in time to be killed by the heating on the second day. Heat- 

 ing on the third day is to make certain that all spores have had 

 time to change to the vegetative stage and be killed. 



LOCKERS AND EQUIPMENT 



Lockers fitted out with apparatus needed in the work of the 

 course are assigned to students. A deposit of 25c is required for 

 the key. This is refunded at the end of the course when the key 

 is returned. The following materials are in each locker : 



1 counting plate 



1 hand lens 



1 platinum needle 



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