Dehydration and Infiltration 71 



Walls {1932) comments that the method offers many advantages: 



I. It will handle anything organic. 

 ^2. It produces no artifacts; no shrinkage or swelling; delicate connections, 



intercellular bridges are preserved. 

 *^3. There is no compression of the sections during sectioning as with 

 paraffin, no disruption of delicate parts. 



4. Sectioning is independent of temperature, humidity, and atmospheric 

 electricity. 



5. Tissues are not rendered brittle or hard. 



6. Mounting is quicker; there is no need for albumen, heating, or drying. 

 N7. Hollow objects section better. 



8. Celloidin supports tissue constantly; tissues cannot be crushed or dis- 

 placed. 



9. Many stains perform better in it. 



10. Time tolerations are great; there is no last minute rush to embed, no 

 worry about tissues staying too long in solutions or hot paraffin. 



In this method toluene cannot be used as a solvent, but there are 

 many other solvents for nitrocellulose. One of the commonest is a com- 

 bination of two so-called latent solvents (not in themselves efficient sol- 

 vents, but possessing excellent solvent qualities when mixed with other 

 compoimds), diethyl ether and ethyl alcohol. The solution is made up 

 of equal parts of the two, ether and absolute ethyl alcohol. 



Dehydration and Infiltration 



The tissue is fixed, Avashed and can be stored in 70% alcohol as usual. 

 The next step is as follows: 



1. 95% ethyl alcohol: 4-24 hours, or longer. 



2. absolute ethyl alcohol, 2 changes: 4-24 hours or longer in each. 



3. ether-alcohol (equal parts of absolute ethyl alcohol and anhydrous 

 ether): 4-24 hours or longer. 



4. 10% nitrocelhUose (dissolved in absolute ethyl alcohol-ether, 1:1): 

 2 days or longer, in a screw-cap jar to keep evaporation to a ixj^ni- 

 mum. 



5. 33-35% nitrocellulose (in absolute ethyl alcohol-ether): 2 days or 

 longer, in tight jar. 



Nitrocellulose solutions should be stored in the dark; light causes the 

 solution to deteriorate. Ferreira and Combs {1951) warn that old light- 

 affected solutions cause fading of nervous tissue blocks. 



