22 CLINICAL BACTERIOLOGY AND H/EMATOLOGY 



METHOD OF EXAMINING CULTURES 



Requisites. I. -Clean slides and cover-glasses. (The latter 

 must be the thinnest in ordinary use i.e., No. I.) 



2. A platinum needle (straight or loop). 



3. A Bunsen burner or a spirit-lamp with a tall flame. 



4. The stain to be employed (see p. 29). 



5. Canada balsam dissolved in xylol. This should be 

 bought ready for use. 



6. A pair of dissecting forceps. 



7. Strips of white blotting"- or filter-paper. 



Process. i. Sterilize the needle, and place a small drop of 

 water (preferably distilled) in the centre of a clean slide. 



2. Take the culture-tube in the left hand between the index 

 and middle fingers with its mouth directed to the right and (in 

 the case of a culture on a solid medium) slightly downward. 



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

 plug with the forceps (previously sterilized by being passed 

 slowly throug'h 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. Sterilize 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 bacteria which it 



. carries are mixed with the water. Now spread out the emul- 

 sion thus produced so as to form a patch about J inch in 



