SECTION THREE 



cooling and thereby obviating crystallization of the wax and conse- 

 quent crumbling of the block when it is mounted on the micro- 

 tome and sections are cut. 



Section Cutting 



This can only be learnt by practical experience under skilled 

 guidance in the laboratory, and it is not proposed to make any 

 attempt to deal with the subject here. However, readers are 

 referred to the specialist books on section cutting. 



Mounting Sections on Slides and Hydrating 



1. Wet the tip of the finger slightly with glycerine albumen 

 (Mayer) and make a smear over an area large enough to take the 

 section in the centre of the slide. 



2. Pick a section up with a needle or forceps and place it over 

 the smear of albumen. 



3. With the thumb, gently press the section on to the smear so 

 that it is quite flat and without folds or creases, taking care not to 

 damage the section in the process. 



Note: If the sections are curled up or folded, first place a drop of 

 1% potassium dichromate on the slide and float the section on 

 this; then heat very gently until the section floats out flat. Blot 

 round the edges of the section to remove excess solution; then 

 carefully but thoroughly blot until all traces of liquid are removed. 

 Leave the slide on a warm surface for a few minutes to drive away 

 the last traces of water ; then proceed as follows : 



4. Gently warm the slide until the paraffin wax just melts; then 

 wash away all traces of wax with two or three changes of xylol. 



5. Remove the xylol by washing the preparation thoroughly 

 with absolute alcohol. 



6. Wash with two changes of 90% alcohol. 



7. Wash with 70% alcohol. 



8. Wash with two changes of distilled water if an aqueous stain 

 is to be used ; but if an alcoholic stain will be used staining may 

 commence immediately after washing with 70% alcohol. 



9. Proceed to stain in accordance with the staining technique it 

 is desired to employ. 



R 501 



