FUNDAMENTAL CONSIDERATIONS 
29 
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 surface 
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 
camels hair pencil into a dish of 70 per cent, alcohol. The sections 
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. 
STAINING AND MOUNTING CELLOIDIN SECTIONS 
1. Place sections in safranin solution for 1 day. This safranin 
solution should be made by dissolving as much safranin in 95 per 
cent, alcohol as it will take up and then diluting with an equal 
quantity of water. 
2. Rinse sections in 50 per cent, alcohol to remove excess of stain. 
3. Transfer them to Delafield’s haematoxylin (made by dissolving 
1 gram of haematoxylin in 6 mils of absolute alcohol and adding 
this gradually to 100 mils of a saturated aqueous solution of ammonia 
alum. This is left exposed for a week, filtered, 25 mils each of 
methyl alcohol and glycerin added, allowed to stand 6 hours, again 
filtered, and ripened about 2 months before using) for 10 minutes. 
