MEDICAL BACTERIOLOGY 



271 



CHAPTER VII 

 PATHOGENIC ANAEROBES 



Anaerobic bacteria may be furnished conditions which permit of 

 their development, in a variety of ways, and a very considerable 

 number of pieces of apparatus have been devised to secure this end. 

 In a general way all of the methods may be grouped under the 

 following heads : 



1. Displacement of air. 



2. Absorption of oxygen. 



3. Exhaustion of air. 



4. Exclusion of air. 



5. Miscellaneous methods, in the presence of reducing substances 

 as litmus, or a strongly aerobic germ, etc. 



The first two methods are the most reliable. In the displace- 

 ment method, hydrogen, carbon dioxide or illuminating gas may 

 be used; hydrogen is best. This gas is readily prepared by the 

 action of sulphuric acid (1:8) 

 on zinc. Either a Kipp gen- 

 erator may be used or one of 

 a simpler construction (Fig. 

 32). The gas should be 

 washed, 1st, in lead nitrate 

 to absorb the sulphuretted 

 hydrogen, 2d, in silver sul- 

 phate to absorb any arseniur- 

 etted or phosphuretted hydro- 

 gen, and 3d, in potassium hy- 

 drate to remove sulphur and 

 carbon dioxide. 



The cultures should be made in dextrose media (which should 

 preferably be freshly prepared and always boiled immediately be- 

 fore being inoculated), either as test-tube or plate cultures. Novy's 

 anaerobic jars are perhaps the most satisfactory receptacles for the 

 cultures. (For description of same, see N. 306.) 



FIG. 32. Hydrogen Generator. 



