FLAGELLA STAINS 105 



The fixing fluid should be prepared some days before use and 

 filtered as required. In colour it should be distinctly violet. 



(b) Sensitising Solution. 



Silver nitrate, 0.5 per cent, aqueous solution. 



This solution must be kept in a dark blue glass bottle or in a 

 dark cupboard. 

 Filter immediately before use. 



(c} Reducing Solution. 

 Weigh out 



Gallic acid 5 grammes 



Tannic acid 3 grammes 



Potassium acetate, fused 10 grammes 



and dissolve in 



Distilled water 350 c.c. 



Filter. 



This solution will keep active for several days, but fresh solution 

 must be used for each preparation. 



METHOD. 



1. Prepare emulsion, make and fix films as above in the preced- 

 ing method, steps i to 4. 



2. Pour on the film as much of the fixing solution as the cover- 

 glass will hold, heat carefully over the flame till steam rises, and 

 allow the steaming fixing fluid to act for five minutes. 



3. Wash well in water. 



4. Wash in absolute alcohol. 



5. Wash in distilled water. 



6. Pour some of the sensitising solution on the film and allow 

 it to act for from thirty seconds to one minute ; blot off the excess 

 of fluid with filter paper. 



7. Without washing, transfer the film to a watch-glass contain- 

 ing the reducing solution and allow it to remain therein for from 

 thirty seconds to one minute; blot off the excess of fluid with 

 filter paper. 



8. Without washing, again treat the film with the sensitising 

 solution, this time until the film commences to turn black. 



9. Wash in distilled water. 



10. Dry and mount. 



To Stain Nuclei of Yeast Cells. 



1. Prepare and fix film in the usual manner. 



2. Soak in ferric ammonia sulphate 3 per cent, 

 aqueous solution for two hours. 



