SECTION THREE 



the removal of the deposits of mercuric chloride which would 

 obscure the picture. 



B. 



A crystal of thymol should be added to the stock 

 bottle. 



Technique: 



1. Sections are mounted on slides and the paraffin wax removed 

 with xylol. If there is any doubt as to the nature of the fixative 

 which has been used, examine a section under the microscope: 

 mercuric chloride, if present, will be seen as a fine brown granular 

 deposit, more abundant in the centre of the section than on the 

 outer edges. 



2. Wash with absolute, followed by 90% alcohol. 



3. Immerse for half to two minutes in Solution A. 



4. Wash well with water. 



5. Immerse in Solution B for half to two minutes or until the 

 natural colour of the sections has been restored. 



6. Rinse well with water. 



7. Stain, dehydrate and clear in the usual manner. 



Method II (Cellosolve Method) 



Simultaneous dehydration of tissue blocks and removal of 

 mercuric precipitates of fixatives 



I. Fix for the required time. 



" 2. Wash for a short time in water or immerse directly in 

 cellosolve. 



3. Immerse in three changes of cellosolve for a total time of 

 twenty-four to forty-eight hours. 



497 



