MEDICAL AND BIOLOGICAL STAINING TECHNIQUES 



17. Transfer to 70% alcohol; then immerse for five minutes in 

 each of two lots of 96% alcohol. 



Note: Absolute alcohol must be avoided as Celloidin is dis- 

 solved by it. 



18. Immerse for five minutes each in two lots of Carbol-Xylol. 



19. Pass into two changes of xylol. 



20. Mount in balsam or Dammar-Xylol. 



{b) Dry Method 



1. Proceed exactly as described above up to and including step 

 No. 8 ; then take the tissue out of the Celloidin and put it into a 

 paper mould as described in step No. 9 (above). 



2. Place the block in a desiccator for a day, lifting the lid for a 

 few seconds every hour or so; then leave in the desiccator over- 

 night. 



3. Next morning place the block in a mixture consisting of equal 

 volumes of cedarwood oil and chloroform and add another 8 vol- 

 umes of cedarwood oil, one volume at a time, every hour for small 

 objects, or every day in the case of large objects. The Celloidin 

 should now be wholly transparent. 



4. Fix the Celloidin block to the wooden or vulcanite block as 

 described in step 10 (above). 



5. Sections may now be cut without the necessity of moistening 

 the knife or the block. 



Note: Blocks prepared by this method are stored in a dry wide- 

 mouth stoppered bottle. 



CELLOIDIN - PARAFFIN WAX (Double Embedding) 

 For serial sections embedded in Celloidin 



Solutions required: 

 Celloidin 1% in Methyl Benzoate 



This is prepared by adding the appropriate weight of air-dried 

 Celloidin flakes to a quantity of Methyl Benzoate in a clean dry 



20 



