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 i 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 i 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 

 i 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. 



