MEDICAL AND BIOLOGICAL STAINING TECHNIQUES 



re-dissolves. A few drops of the reserved silver 

 nitrate are then added, with shaking, until the final 

 solution is slightly opalescent. 



Technique: 



1. Air-dried films are flooded with Solution A for one minute; 

 then washed with distilled water. 



2. Flood with Solution B and heat until steam arises ; then pour 

 ofi^ and allow the slide to cool somewhat before rinsing with dis- 

 tilled water. 



3. Flood with Solution C; heat till steam rises; then allow the 

 solution to act for one half to one minute. 



4. Wash with distilled water; dry and blot in air; and mount 

 before examining as the stain may fade immediately in contact 

 with immersion oil. 



Result: 



Spirochaetes are stained dark brown to black, against a maroon 

 background. 



GENTIAN VIOLET (Noland) 

 A combined fixative and stain for Protozoa 



Solutions required: 



Gentian violet 2% aqueous . . i ml. 



Phenol, saturated aqueous . . . . 80 ml. 



Formaldehyde 40% . . . . . . 20 ml. 



Glycerin . . . . . . • • 4 rnl- 



Technique : 



1 . Place a drop of the culture to be examined on a scrupulously 

 clean slide. 



2. Add a drop of the staining solution and mix and spread with 

 a platinum wire loop into a film. 



3. Allow to dry; then examine under the oil immersion ob- 

 jective. 



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