BACTERIOLOGICAL TECHNIC. 89 



taining bouillon broth, blood serum, milk and other media with or without 

 indicators. 



C. Studying Anaerobic Microbes. — Some microbes have anaerobic tend- 

 encies (facultative aerobes) and some are absolutely anaerobic (obligative 

 anaerobes). The deep stab culture will show anaerobic tendencies. If 

 such tendency exists, development will be more active near the bottom of 

 tube (in the line of the stab). The culturing of obligative anaerobes re- 

 quires special apparatus though the methods are not in any way difficult. 

 The following methods are used: 



a. Deep stab culture. This has already been sufficiently explained. It 

 merely indicates possible anaerobic tendencies. 



b. High-culture methods. Fill the tube of a deep stab culture, shallow 

 stab or streak, with liquid agar or gelatin and incubate in the usual way. 

 The medium to be poured must not be warmer than is absolutely necessary 

 to render it liquid. This brings out possible anaerobic tendencies to a more 

 marked degree than does the simple deep stab culture. 



c. Make an Esmarch roll tube culture as follows: Roll a dilution 



^//////MMm/m///////A 



Fig. 42. — Hanging-drop culture, sectional profile view. These slides can be procured 

 from dealers in microscopical supplies. 



gelatin or agar tube culture (1:10, 1:100, 1:1000, etc.) so that all of the 

 medium (5 c.c, 9 c.c. to 10 c.c.) is spread oyer the inner surface of the tube 

 to within a short distance of the cotton plug. Keep on rolling slowly until 

 the medium has set. Roll on ice, under the tap water, in ice water, holding 

 the tube at the proper slant. When the medium has set, fill in the entire 

 tube with liquefied gelatin or agar; cool, and incubate. Like the other 

 methods described, this will show possible anaerobic tendencies. 



d. Various methods are used to either remove the air (vacuum), dis- 

 place the air, or remove the oxygen from the air. In the so-called Buchner 

 method, potassium hydroxide and pyrogallic acid are used to take up the 

 oxygen of the air. The air in a suitable container may be replaced by 

 hydrogen by means of a Kipp generator. As it is not likely that the phar- 

 macist will have any occasion to employ these methods we shall pass them 

 by with this mere mention. The full description of the methods will be 

 found in any of the larger works on medical bacteriology XJr in the larger 

 text-books on bacteriological technic. 



D. Microscopical Examination of Microbes. — The compound microscope 

 is used in examining hanging-drop cultures, water mounts and cover-glass 

 preparations. To make a hanging-drop culture, hollow ground slides 



