30 BACTERIOLOGICAL DIAGNOSIS. 



3. Burn the surface of the plug in the flame. Remove 

 the plug with the forceps (previously sterilised by being 

 passed slowly through the flame) and place it between 

 the ring and little fingers of the left hand. Lay the 

 forceps down. 



In cases where you are examining the culture for 

 diagnostic purposes only, and do not care if it becomes 

 contaminated during the process, it is unnecessary to 

 take these precautions. The cotton-wool plug may 

 then be removed with the fingers and laid down on the 

 table. As a matter of fact very few cultures do become 

 contaminated even if no precautions are taken. 



4. Sterilise the needle in the flame and allow it to 

 cool. 



5. Now introduce the needle into the tube and take 

 up a small portion of the growth, taking care not to 

 scrape up the surface of the medium as you do so. 

 Most beginners fall into the mistake of taking up far 

 too much of the growth, and preparing a film which is 

 spread so thickly that the individual bacteria cannot 

 be distinguished. 



6. Take the plug up in the forceps, burn its surface 

 in the flame, re-plug the tube and lay it down. 



7. Stir the droplet of water which has been deposited 

 on the slide with the tip of the needle so that the bac- 

 teria which it carries are mixed with the water. Now 

 spread out the emulsion thus produced so as to form a 

 patch about half an inch in diameter. If it does not 

 spread out uniformly it is a sign that the slide is not 

 clean. 



8. Sterilise your needle. 



9. Allow the film to dry spontaneously. If you have 

 spread it out sufficiently this will take a very short time. 



10. Fix the film by passing the slide slowly through 



