MEDICAL AND BIOLOGICAL STAINING TECHNIQUES 



Technique: 



1. Filter about ten drops of the sudan black solution, which 

 should be two or three days old, into a test-tube. 



2. Emulsify bacteria from a slant culture directly into the fil- 

 tered Sudan black in the test-tube. 



3. Allow the tube to stand undisturbed for fifteen to twenty 

 minutes until the precipitate has settled. i 



4. On a scrupulously clean slide place a loopful of the emulsion 

 from the top and smear with a circular motion to facilitate rapid 

 drying. 



5. Stain with the safranin solution for about fifteen seconds. 



6. Wash with distilled water; drain. 



7. Blot dry, and examine under the oil-immersion objective. 



Results: 



Bacterial cells are stained pink ; fatty material is bluish grey or 

 blue-black. 



Note: With reasonable care, unmounted smears will remain 

 unchanged for at least six months. 



From J. Bact.y 43, 717-24, 1942, Burdon, K. L., Stokes, J. C, and Kim- 

 brough, C. E. " Studies of the common aerobic spore-forming bacilli ". 



SUDAN 3 



A stain for blood in the spinal fluid, differentiating fresh 



haemorrhage from old 



Solution required: 

 Sudan 3, saturated in 70% alcohol. 



Technique: 



1. Smears of spinal fluid are made on scrupulously clean slides 

 and allowed to dry thoroughly in the air for about half an hour. 



2. Without fixing, immerse in the sudan 3 solution for five to 

 fifteen minutes, in a stoppered staining jar. 



3. Rinse well with distilled water ; then immerse for one minute 

 each in four or five changes of distilled water. 



398 



