STAINING, PRACTICAL AND THEORETICAL 



(b) Fixatives containing metals must be avoided. 



(c) Tlie use of metal instruments in handling the sections must 

 be avoided. 



Solutions required: 



A. Gum acacia io% aqueous, filtered lOO ml. 

 Silver nitrate, A.R. grade . . 2 gm. 



Note: This solution should be prepared immedi- 

 ately before use. 



B. Gum acacia 10% aqueous, filtered 100 ml. 

 Hydroquinone . . . . . . i gm. 



Note: This solution should be prepared the day 

 before it is required for use. 



C. Solution A . . . . . . 10 ml. 



Solution B . . . . . . 10 ml. 



Citric acid 5% . . . . . . 0-5 ml. 



Note: This solution should be prepared only 

 when required for immediate use. 



D. Sodium thiosulphate 5% aqueous. 



Technique: 



1. Small pieces of tissue are fixed in 20% formalin, and frozen 

 sections are employed. 



2. Rinse thoroughly in distilled water. 



3. Immerse sections in Solution C and leave therein for five to 

 ten minutes. 



4. Plunge sections directly into the sodium thiosulphate solu- 

 tion, without prior washing, and leave therein for five minutes. 



5. Wash thoroughly in several changes of distilled water. 



6. Mount in Aquamount or in Farrant's medium. 



Results: 



The presence of gold is indicated by a black deposit in the cells. 



Reference: Roberts, W. J. (1935). 



408 



