STAINING, PRACTICAL AND THEORETICAL 



4. Clear in two changes of toluene or benzene for a total time 

 of one to two hours. 



5. Embed in paraffin wax as usual. 



Results: 



The mercuric precipitates are completely eliminated from the 

 tissues. 



Notes: 



This method not only saves time in the embedding process but 

 when the tissues have been fixed in fluids containing mercury 

 compounds, it also obviates the use of iodine and sodium thio- 

 sulphate (page 497), and in consequence, the mordant action of 

 iodine also. It would appear that the needle crystals or spots 

 deposited in tissues which have been fixed in fluids containing 

 mercury compounds, which according to Baker (1950) represent 

 a reaction product between mercuric chloride and tissue phos- 

 phates, are soluble in cellosolve and are thus dissolved and 

 washed away. 



Reference: Gonzalez, G. (1959). 



PARAFFIN WAX EMBEDDING AND SECTIONING 



(a) Dehydration 

 Technique: 



1 . Pieces of tissue are fixed and washed by any of the standard 

 methods. 



2. Immerse in 50% alcohol from twelve to twenty-four hours. 



3. Transfer to 70% alcohol for the same length of time as 

 stage 2. 



4. Transfer to 90% alcohol for the same length of time. 



5. Transfer to 96% alcohol for the same length of time. 



6. Immerse in absolute alcohol for the same length of time. 



Note: Where possible use a series of corked specimen tubes for 

 the above procedures. By occasionally shaking the tube containing 

 the specimen the process of penetration of the alcohol is acceler- 

 ated. Twelve hours in each change of alcohol is sufficient for small 

 pieces, but larger pieces of tissue usually require eighteen or 



498 



