SECTION THREE 



Technique: 



1. To locate the sites of saponin immerse sections in the barium 

 hydroxide solution for sixteen to twenty-four hours ; then examine 

 under the microscope and observe the insoluble colourless com- 

 pound formed by the interaction of saponin and barium. 



2. Wash well with the calcium chloride solution. 



3. Cover with the potassium dichromate solution and watch the 

 reaction under the microscope. 



Results: 



The insoluble substance first formed between the barium and 

 saponin is broken down, the barium uniting with the chromium, 

 forming barium chromate, which is identified by its yellow colour. 

 Cells containing tannin assume a rich brown colour during the 

 reaction. 



Sodium 



Solution required: 

 Uranium acetate, saturated aqueous. 



Technique: 



1. Sections are placed in a few drops of the reagent on 

 a slide. 



2. Add one drop of hydrochloric acid to the preparation. 



3. Place uncovered slides in a desiccator to facilitate the slow 

 evaporation of the reagents. 



4. Examine at hourly intervals over a maximum period of eight 

 hours. 



Results: 



Pale yellow rhomboidal or tetrahedral crystals (sodium uranium 

 acetate) indicate the presence of sodium in the tissue. 



Note: The presence of magnesium is indicated by large rhom- 

 boidal crystals, with this technique. 



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