CHAPTER III. 



Principles of sterilization by heat— Methods employed — Discontinued 

 sterilization — Sterilization under pressure— Apparatus employed — Chemical 

 disinfection and sterilization. 



In the laboratory it is often common 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 thcM'ord sterilization for 

 the destruction of bacteria by high temperatures proba- 

 bly arose from the circumstance that culture media and 

 certain other articles that it is desirable to render abso- 

 lutely free from bacterial life are not treated by chemical 

 agents for this purpose, but are exposed to the influ- 

 ence 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 com- 

 pounds possessing germicidal properties, i. e., to the 

 action of disinfectants ; and the process is, therefore, 

 known as disinfection, though the same end can be 

 reached by the application of heat to these articles also. 

 Strictly speaking, sterilization implies the complete 

 destruction of the vitality of all micro-organisms 

 that may be present in or upon the substance to be 



