APPENDIX A 125 



change in the liquids thus treated. In milk the bacteria are likewise 

 killed, but there is a complete or partial destruction of the enzymes 

 of normal milk. Other workers, like Schwarz and Aumann, have 

 found that complete sterilization is frequently not obtained, although 

 the bacterial content is greatly reduced. 



The process of sterilization by this means seems promising for 

 laboratory work and, when better developed, ought to be of great 

 assistance to the bacteriologist. Whether it will be of equal value to 

 the engineer remains to be seen. 



THE TECHNIQUE OF STERILIZATION FOR 

 SPECIAL PURPOSES 



1. Glassware, pipettes, and instruments. The most effective method 

 of sterilizing these articles is in the hot-air sterilizer. Objects to be 

 sterilized should be perfectly clean, dry, and free from dust. Flasks 

 should be plugged with cotton, and the plugs may be covered with 

 paper caps. Petri dishes, unless they are to be used immediately, 

 should be wrapped in manila paper or inclosed in the sheet-iron 

 cases made for the purpose. Pipettes should have the large end 

 plugged with absorbent cotton and should be sterilized in sheet-iron 

 boxes or wrapped in paper. Knives, scrapers, scalpels, forceps, 

 needles, and spatulas may be sterilized, at the time of using them, 

 in a gas flame. If they cannot be used while hot, they should be 

 sterilized in a sheet-iron box, as pipettes, or in large test tubes 

 plugged with cotton. 



Where time or facilities will not permit of hot-air sterilization, 

 the articles mentioned above may be sterilized with chemicals. 

 Pipettes may be sterilized by drawing up alcohol of 50-70 per cent 

 strength and rinsing the pipette with sterile distilled water or with 

 the solution to be employed. Flasks may be rinsed with alcohol or 

 mercuric bichloride solution and rinsed with sterile water or the test 

 solution. Instruments may be washed with a 1 per cent solution of 

 lysol or tricresol and dried on sterile surgeon's gauze. Wherever 

 possible, however, sterilization by heat is to be preferred. 



2. Liquid media and other solutions. For general work solutions 

 are -most easily and thoroughly sterilized in the Arnold sterilizer or in 

 the autoclave. They may also be sterilized by heat on a steam bath 

 or, if organic compounds be absent, by boiling over a flame, although 

 in the latter case it is difficult to avoid steaming the cotton plugs. 



