116 Manual of Veterinary Microbiology. 



Seat. — As we already know, bacteria and their 

 spores are killed by heat. For this it is necessary 

 that the objects which contain the germs be raised to 

 a temperature varying according to the case. There 

 are several processes. 



a) Flaming. — Objects which can support the ac- 

 tion of a rather high temperature are brought into 

 the flame of a spirit lamp and subjected, in all their 

 parts, to a temperature of about 200°. Flaming is 

 practiced chiefly for glassware, occasionally for metal- 

 lic instruments: spatulas, platinum wire. 



6) Dry air ovens at 150° C. — The objects to be steril- 

 ized are kept for about two hours at a temperature 

 of 150°. To this end they are placed in appropriate 

 ovens, furnished with a temperature regulator and 

 arranged in such a manner that the temperature, 

 through the_circulation of hot air, is nearly the same 

 in all parts of the apparatus. These ovens are pro- 

 tected from too free radiation by walls composed of a 

 substance which is a bad conductor of heat, such as 

 asbestos. Sterilization by this process is practiced 

 chiefly on glassware, wadding and metallic objects. 



c) Koch's steam sterilizer. — This is a generator of 

 steam, of cylindrical form, containing water which is 

 kept in ebullition by the combustion of gas ; it is sur- 

 mounted by a dome of plate tin enveloped in felt to 

 prevent cooling. The temperature of the cylinder, 

 charged with steam, is maintained at 100°, a tempera- 

 ture sLifiicient for the destruction of germs and spores 

 in the moist state. Objects to be sterilized must be 

 left in the upper part of the apparatus from two to 

 three hours. The steam sterilizer is employed chiefly 



