PREPARATION OF UTENSILS. 59 



Tubes which contain old culture media or growths 

 should, after removal of the cotton stoppers, be placed 

 in 5% carbolic acid for 24 hours. The tubes should 

 then be boiled in a 5% solution of washing soda for \ 

 hour. This softens and allows the ready removal of 

 any remaining material in the tubes. The tubes are 

 then rinsed in water and treated like new tubes. 



Slides. New slides need no particular treatment be- 

 fore use. Slides used, should be placed in turpentine 

 for 24 hours, so as to free the cover glasses. On removal 

 from the turpentine rinse through " waste " alcohol and 

 then in water. Boil for a few minutes in 5% solution 

 of washing soda, and again rinse in water, and dry. 

 Slides may then be kept in alcohol. 



Glassware. Thorough rinsing in water suffices for 

 the cleaning of all glassware not contaminated with 

 culture media, or like material. When so contaminat- 

 ed boil in 5% solution of washing soda, and then rinse 

 in water. Flasks should be rinsed in methylated spirit 

 and allowed to dry, before sterilization. Sterilization is 

 effected in the hot air sterilizer at 150° to 300°C, for one 

 hour. 



Instruments. Knives, scissors, forceps and hypo- 

 dermic needles are best sterilized by boiling from 5 to 

 10 minutes, after protecting any cutting edges by wrap- 

 ping absorbent cotton about them. Sterilization may 

 also be effected in 5% carbolic acid solution or in 

 1% formalin, exposing the instruments to their action 

 for at least i hour. Sterilization is readily and rapidly 

 effected, by placing the instruments in the flame, but of 



