. The principles of bacteriology: a practical manual for students and physicians. accumulation of gas in closed arms of thetubes. Third, as to the capacity of each solution forreducing copper in Fehlings solution. What differ-ences are observed, and how may they be explained? Cultivation without Oxygen.—As we havealready learned, there is a group of bacteria to whichthe designation anaerobic has been given, whichare characterized by inability to grow in the presenceof free oxygen. For the cultivation of the members ofthis group, a number of devices are employed for theexclusion of free oxygen
. The principles of bacteriology: a practical manual for students and physicians. accumulation of gas in closed arms of thetubes. Third, as to the capacity of each solution forreducing copper in Fehlings solution. What differ-ences are observed, and how may they be explained? Cultivation without Oxygen.—As we havealready learned, there is a group of bacteria to whichthe designation anaerobic has been given, whichare characterized by inability to grow in the presenceof free oxygen. For the cultivation of the members ofthis group, a number of devices are employed for theexclusion of free oxygen from the cultures. Kochs method. Koch covered the surface of a gela-tin plate, wliich had been previously inoculated, witha thin sheet of sterilized isinglass. The organisms CVLTIVATION WITHOUT OXYGEN. 217 which grew beneath it were supposed to develop with-out oxygen. Hesses method. Hesse poured sterilized oil upon thesurface of a culture made by stabbing a tube of growth that occurred along the track of the needlewas supposed to be anaerobic in nature. Fig. Liborius tube for anaerobic cultures. Methods of Liborius. Liborius has suggested twouseful methods for this purpose. One is to nearly (aboutthree-quarters) fill a test-tube with gelatin or agar-agar,which, after having been sterilized, is to be kept in avessel of boiling water for ten minutes to expel all airfrom it. It is then rapidly cooled in ice-water, andwhen between 30° and 40° C, still fluid, is to be inoc-ulated and very rapidly solidified. It is then sealed inthe flame. Anaerobic bacteria develop only in the lower 218 BACTERIOLOGY. layers of the medium. In his other method he employsa special tube, known as the Liborius tube. Its con-struction is shown in Fig. 41. Through the side tube hydrogen is passed until it re-places all the air; the contracted parts, both of the neckof the tube and the side arm, are then sealed in theflame. This tube can be used for either solid or liquidmedia, but, ow
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