46 STERILIZATION. 
test-tubes stopped with a cotton-wool plug remain 
sterile indefinitely. 
I. Steam Sterilization. 
Ber objects liable to be injured by dry heat, such 
Fic. 22.—Kitasato’s fil- 
ter: a, porcelain bougie ; 
6, attachment for suction- 
pump; ¢, reservoir; d, 
sterile receiver. 
as culture-media, fluids, in- 
struments, etc.: 
(a) Fill the water-tank 
of the sterilizer’ and start 
the flame. 
(6) When the chamber is 
filled with steam place the 
objects ,to be sterilized 
within and close the door. 
(c) If the objects will not 
be injured by prolonged 
heating, allow them to re- 
main for one hour. 
(2) If prolonged heating 
is injurious, allow them to 
remain twenty minutes, 
and repeat the process 
three times at intervals of 
twenty-four hours. 
II. Steam Sterilization under Pressure. 
For rapid and effective sterilization. In this 
method an ‘‘ 
autoclave’’ is used. 
(a) Adjust the safety-valve at the desired press- 
ure, say thirty pounds. 
See that an abundance of water is present, so that 
the steam will not be superheated. 
? An “Arnold”? sterilizer is the form usually employed. 
