SECTION TWO 



Results: 



Background, dull yellow. Nerve cells and their processes, 

 black. Blood vessels, black. 



Reference: Golgi, C. (1875). 



GRAM'S IODINE 

 For bacteria in sections 



Solutions required: 



A. Carbol gentian violet. 



B. Gram's iodine. 



C. Carbol fuchsin (Ziehl Neelsen) . . i volume 

 Distilled water . . . . • • 9 volumes 



D. Picric acid, saturated, aqueous. 



Technique: 



1. Pieces of tissue are fixed in 10% formalin; dehydrated; 

 cleared and embedded in paraffin wax. 



2. Fix sections to slides; dewax and take down to distilled 

 water in the usual manner. 



3. Stain in Solution A for about two minutes. 



4. Pour off excess stain and without washing add Gram's 

 iodine and allow the stain to act for one minute. 



5. Differentiate in pure acetone until colour ceases to come out 

 of the sections. 



6. Counterstain in the carbol fuchsin (Solution C) for about a 

 minute. 



7. Pour off excess stain, and drain, without allowing the sections 

 to dry; then without washing: 



8. Cover the sections with the picric acid solution, pouring off 

 after one half to one minute. 



9. Dehydrate and clear with pure acetone for about fifteen 

 seconds. 



10. Clear in xylol and mount. 



Results: 



Gram-positive organisms are stained violet, while Gram- 

 negative are red. Nuclei are stained pink, while cytoplasm is 

 yellow. 



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