THE METHODS OF STERILIZATION. 



83 



7. For applying moist heat, bacteriologists commonly use 

 a. Koch's apparatus (Fig. 40). b. Arnold's apparatus (Fig. 41). 



8. For the application of steam under pressure preference 

 is felt for the autoclave of Chamberlain or of Wiesnegg 

 (Fig. 42). 



9. For discontinuous fractional sterilization at a low tem- 



FIG. 42. 



Vk. 



A B 



Autoclave, pattern of Wiesnegg: A, external appearance; B, section. 



(Abbott.) 



perature the apparatus in more general use is the blood-serum 

 sterilizer of Koch (Fig. 43). 



10. Filtration under pressure through unglazed porcelain, the 

 pores of which are too small to allow bacteria to go through, 

 will render certain liquid substances sterile or bacteria-free. 

 This method is made use of in the case of certain pathogenic 

 bacteria which secrete soluble poisons which we desire to 

 separate from the bacteria themselves. The Chamberlain 



