Il6 PHARMACEUTICAL BACTERIOLOGY 



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 

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

 medium (5 cc. to 10 cc.) is spread over 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. 



E%%%%i^^ 



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

 from dealers in microscopical supplies. 



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 or in the larger 

 text-books on bacteriological technic. 



D. Microscopical Examination of Microbes. The compound micro- 

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

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

 (concave center) are required. Touch a small drop of the culture to be 

 examined on the center of a clean and heat-sterilized cover-glass, by means 

 of a heat-sterilized platinum wire loop. Smear a little plain petrolatum 

 around the rim of the concavity of the slide and invert the cover-glass prep- 

 aration upon the slide, pressing it gently in place on the petrolatum. 

 Examine for a period of several hours or longer as may be desired. Cell 

 division, spore formation, etc., can be studied very conveniently. Ob- 

 servations on the effects of temperature and rate of septation may be 

 made. The hanging-block preparation is made by touching the surface of 

 a cube of nutrient agar with the bacteria and then applying this bacterial 

 side against the cover-glass and mounting like the hanging drop. The 

 bacteria will be found close to the cover-glass. 



Bacteria can be examined mounted in water on a slide covered with 

 cover-glass, in order to make observations regarding motility. Of course 

 it is not desirable to examine pathogenic microbes in this manner because 



