20 GENERAL BACTERIOLOGY LESSON 



(c) Place the films in 20 per cent acetic acid for three to 

 five minutes. 



(d) Wash them in water, dry them between folds of 

 blotting-paper, and pass them again through the flame. The 

 films are now ready for staining. 



(1) Lqffler's methylene-blue. 



(a) Place one film in the stain for two to five minutes. 



(b) Wash in water, dry and mount in xylol balsam. 



Examine with -^ in. oil immersion : observe the 

 leucocytes and cocci (Staphylococci or Streptococci, 

 or both many probably in the leucocytes). 



(2) Gram's method. 



(a) Place the other film in absolute alcohol for one to 

 two minutes. 



(b) Stain it in aniline gentian- violet for one to two minutes. 



(c) Remove the superfluous stain with blotting-paper. 



(d) Now place in Gram's solution of iodine for half a 

 minute, until the specimen turns black. 



(e) Soak up the superfluous iodine solution. 



(/) Wash in alcohol till the film is almost colourless. 



(g) Pass quickly through a diluted alcoholic solution of 

 eosine, which stains the leucocytes and ground substance 

 pink. 



(h) Wash in water, dry and mount in xylol balsam. 



Examine with a high power, and then with j^- in. oil 

 immersion : the pus cocci are stained dark violet, 

 and also the chromatine of the nuclei ; the ground 

 substance and protoplasm of the leucocytes are pink. 



