700 PHARMACEUTICAL BOTANY 
stage. From this point the various succeeding steps in the 
procedure are as follows: 
1. Place material in equal parts of 95 per cent. alcohol and 
ether (known as ether-alcohol) for several hours. 
2. Transfer to a 2 per cent. solution of celloidin in ether- 
alcohol, for 2—5 days. 
3. Transfer to a 6 per cent. solution of celloidin in ether- 
alcohol, for 2—5 days. 
4. Transfer to a 12 per cent. solution of celloidin in ether- 
alcohol, for 3-10 days. 
5. Prepare a pine block sufficiently large in cross section to 
support the material and otherwise adapted to its being clamped 
in the object carrier of the microtome. Soak one end of this 
block in ether-alcohol for a while and then dip it in the 2 per cent. 
celloidin solution. 
6. ‘Take the material from the thick celloidin and set it in 
proper position, for cutting the sections desired, on the prepared 
end of the block and allow the celloidin to thicken for a few 
seconds only. 
7. Dip the celloidin end into the thick solution; remove and 
hold upright so that the new coating may spread out over the 
end of the block and solidify the union. : 
8. As soon as the celloidin has hardened a little to form a sur- 
face film, drop the preparation into a vessel of chloroform and 
allow to remain here 1 day. 
9. Transfer preparation to a vessel containing equal parts of 
glycerin and 95 per cent. alcohol until required for sectioning. 
SECTIONING CELLOIDIN MATERIAL 
Clamp the block in the sliding microtome and set the knife 
obliquely so that the sections can be cut with a long sliding stroke. 
Keep the knife and top of the block wet with the alcohol-glycerin 
mixture and as soon as the sections are cut, sweep them with a 
camel’s hair pencil into a dish of 70 per cent. alcohol. The sec- 
tions can be attached to a slide by placing the slide in a closed 
chamber over ether. The ether vapor dissolves the celloidin and 
causes the sections to adhere to the slide. 
