CHAPTEE III, 



Principles of sterilization by heat — Methods employed — Discontinued 

 sterilization— Sterilization under pressure— Apparatus employed— Chemical 

 disinfection and sterilization. 



Most important for the proper performance of bac- 

 teriological manipulations are acquaintance with the 

 principles underlying the methods of sterilization and 

 disinfection, and familiarity with the approved methods 

 of applying these principles in practice. 



In many laboratories it is customary to employ the 

 term sterilization for the destruction of bacteria by heat, 

 and the term disinfection for the accomplishment of the 

 same end through the use of chemical agents. This 

 distinction in the use of the terms is not strictly correct, 

 as we shall endeavor to explain. 



The laboratory application of the word sterilization for 

 the destruction of bacteria by high temperatures prob- 

 ably arose from the circumstance that culture media, 

 and certain other articles that it is desirable to ren- 

 der absolutely free from bacterial life, are not treated 

 by chemical agents for this purpose, but are exposed to 

 the influence of heat in various forms of apparatus 

 known as sterilizers; and the process is, therefore, 

 known as sterilization. On the other hand, cultures 

 no longer useful, bits of infected tissue, and apparatus 

 generally, that it is desirable to render free from danger, 

 are commonly subjected for a time to the action of chem- 

 ical compounds possessing germicidal properties — i. e., 



