CHAPTER 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 is an acquaintance with the 

 principles underlying the methods of sterilization and 

 disinfection, and a familiarity with the approved meth- 

 ods 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 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 chemical 

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



