30 BACTERIOLOGICAL DIAGNOSIS. 
3. Burn the surface of the plug inthe 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. Asa 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 forma 
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. 
g. 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 
