18 MICROSCOPIC TECHNIQUES 



PROCEDLUE 



1. Transfer frozen or parafl5n sections which have been washed 

 with distilled water to the silver nitrate soln. in the dark for up to 1 

 hr. ; wash with distilled water in the dark, and expose to bright hght 

 for 30 min. or longer. 



2. Wash well in distilled water, dehydrate, clear, and mount. 

 Result. Calcium salts are rendered black. 



MAGNESIUM 



A method for the demonstration of magnesium in plant cells was 

 developed by Broda ( 1939) . The principle of this method could be 

 adapted to studies on animal tissue. Most of the tests used for 

 calcium also give positive results for magnesium. 



Broda Method for 3Iagnesiuin 



SPECIAL REAGENTS 



Quinalizarin Reagent. Triturate 100 mg. quinalizarin and 500 mg. 



sodium acetate crystals, and dissolve 500 mg. of the mixture in 



100 ml. of 5% sodium hydroxide. 

 0.2% Titian Yellow. 

 10% Sodium Hydroxide. 

 0.1% Azo Blue. 



PROCEDURE 



1. Prepare paraffin sections as usual. 



2. Add 1-2 drops of quinalizarin reagent to a section on the slide, 

 followed by 1-2 drops of 10% sodium hydroxide. 



3. To a different section add 1-2 drops of the Titian yellow 

 solution followed by 1-2 drops of 10% sodium hydroxide. 



4. To another section add a drop or two of the azo blue dye. 

 Result. In the presence of magnesium the quinalizarin reagent 



develops a blue color over several hours, the Titian yellow a brick- 

 red, and the azo d3'e a violet stain. 



ZINC 



Very little has been done in regard to the histological localization 

 of zinc and the procedure of Mendel and Bradley (1905) is still 



