240 



Journal of Applied Microscopy. 



The filtered agar is then filled into tubes and sterilized in steam for thirty 

 minutes on each three successive davs. 



Fig. 4. 



Fig. 



STERILIZATION. 



The tubed media are always sterilized in steam. If an autoclave (Fig. 4) is 

 at hand, a single steaming at 11 "i degrees C. for fifteen minutes will be sufficient, 



otherwise it is necessary to resort to fractional 

 sterilization, in which case the material is 

 steamed on each of three consecutive days. 

 This is done in order to allow the spores that 

 may be present an opportunity to germinate. 

 \'arious steam sterilizers are used for this 

 purpose. The Koch sterilizer (Fig. n) and 

 that of Arnold (Fig. G) are well known. In 

 the author's laboratory, where there are seventy- 

 five students at work at the same time, the 

 use of these sterilizers has been found unsatis- 

 factory. They have been replaced by small 

 copper pails which are placed upon the water- 

 b?ith. 



At a very small outlay, each student is 

 provided with his own .sterilizer. Conse- 

 quently, no time is wasted in waiting either 

 for a .sterilizer or for the water to boil. For 

 the details of construction, the reader is re- 

 i"- i; ferred to this journal, vol. 1, page oH. 



STERILIZI^4G CHAMBER 



