AGAR HANGING-BLOCK CULTURE 81 



3. Place the ring on the slide and press it down gently 

 to make contact complete. The vaselin renders the cham- 

 ber water tight. 



4. Seal the ring to the slide with melted paraffin as in 

 the adhesion culture, to keep it from slipping around. 



5. With a sterile pipette convey into this chamber 

 just enough (boiled) water to cover the bottom. 



6. Vaselin the upper edge of the ring. 



7. Inoculate lightly the tube of liquid medium with the 

 organism to be studied. Distribute throughout the liquid 

 with the needle. 



8. Transfer one loopful to a cover-glass. 



9. Using the straight needle, spread in a thin film over 

 the entire surface of the cover-glass. If any of the liquid 

 adheres in droplets, shake them off. 



10. Press the cover-glass, medium side down, upon the 

 upper vaselined edge of the ring. 



11. Seal the edge of the cover-glass to the glass ring in 

 several places with paraffin to prevent it from slipping 

 around. 



12. Incubate at the desired temperature. 



This possesses some advantages over the adhesion cul- 

 ture, as more air and moisture and consequently more favor- 

 able conditions are furnished for growth. With a little 

 more delicate manipulation agar or gelatin can be used 

 in place of the liquid medium. 



EXERCISE 24. PREPARATION OF AGAR HANGING- 

 BLOCK CULTURE 



This method was devised by Hill * for studying to 

 better advantage the morphology and manner of multi- 

 plication of bacteria. 



Carry out this procedure in a special plating room or 

 chamber if possible, to avoid contamination from air cur- 

 rents. 



*Hill, Journal of Medical Research, Vol. VII, March, 1902, p. 202. 



