STAINING, PRACTICAL AND THEORETICAL 



Technique: 



1. Fix a piece of tissue not more than 3 mm. thick in the for- 

 maldehyde-saline for an hour. 



2. Transfer, without washing, to the dichromate formaldehyde 

 (Solution D) and leave for five hours. 



3. Transfer, without washing, to 5% aqueous potassium 

 dichromate and leave for about eighteen hours. 



4. Leaving the tissue in the same solution, transfer to the paraf- 

 fin oven at 60° C. for twenty-four hours. 



5. Wash in running water for six hours. 



6. Leave overnight in the melted gelatine in the oven at 37° C. 



7. Cool the gelatine, preferably in a refrigerator. 



8. Cut out a rectangular block containing the specimen. 



9. Immerse the block overnight (or any conveniently longer 

 time) in formalum, placing a marble chip in the capsule or tube. 



ID. Cut sections 8 to lo/z on the freezing microtome. 



11. Transfer a section to 70% alcohol. 



Note : It is best to transfer sections from fluid to fluid, up to stage 

 16 in a Royal Worcester Porcelain thimble No. ^.4756, size 2. 



12. Transfer to the Sudan black solution, and leave for I-4 

 minutes. (The best period is usually about 2| minutes.) 



13. Wash in 70% alcohol for five seconds. 



14. Wash in 50% alcohol for one minute. 



15. Wash in water, sinking the section gently with a camel hair 

 brush if it floats. 



16. Transfer to Carmalum for two to three minutes. (The 

 optimum time is usually three minutes.) 



17. Rinse in distilled water. 



18. Transfer the section to a fairly large dish, or a tongue jar 

 of tap water, and leave for two minutes, or any conveniently longer 

 time. 



19. Wash again in another large bowl of water. 



20. Transfer to a petri dish of water. 



21. Float the section on to a slide. 



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