. A laboratory guide in bacteriology, for the use of students, teachers and practitioners. Bacteriology. l6 LABORATORY GUIDE IN BACTERIOLOGY At the end of this period the gas is shut off and the pressure allowed to decrease gradually. The valve should not be opened, nor the lid removed, until atmospheric pressure has been restored, otherwise the sudden release of pressure would cause the media to boil suddenly and push the plugs out of place. When large autoclaves are used (Fig. lo) pro- vision must be made for proper circulation of air, or "air cushions" form and media will not be s
. A laboratory guide in bacteriology, for the use of students, teachers and practitioners. Bacteriology. l6 LABORATORY GUIDE IN BACTERIOLOGY At the end of this period the gas is shut off and the pressure allowed to decrease gradually. The valve should not be opened, nor the lid removed, until atmospheric pressure has been restored, otherwise the sudden release of pressure would cause the media to boil suddenly and push the plugs out of place. When large autoclaves are used (Fig. lo) pro- vision must be made for proper circulation of air, or "air cushions" form and media will not be sterilized. If an aperture remains in the outlet the discharge of air is facili- tated. Attachment of a vacuum pump is often desirable to remove all air. Blood serum or egg media are the most diffi- cult to sterilize. The tem- perature of coagulation of these media is relatively low, and sudden heating causes the mass to break up, form bubbles, and be- come useless for cultural purposes. The Koch inspis- sator may be used, or, with certain precautions, the autoclave. The Koch inspissator (Fig. ii) allows the tubes to rest in an inclined position and to be heated gradually to 75° C. This temperature is maintained. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Heinemann, Paul Gustav. Chicago, Ill. , The University of Chicago Press
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