APPENDIX 305 



before staining if the sections hold together well ; if they do not 

 the celloidin should be dissolved after staining and fixing to the 

 slide. 



Mounting. Sections in which the celloidin is not stained 

 may be mounted in glycerine or in balsam without removing 

 the celloidin. 



In mounting in balsam, when the celloidin is not to be 

 dissolved, the sections are placed in 95 p.c. alcohol to remove 

 most of the water ; then in origanum oil or cajeput oil (neither 

 of these dissolves aniline colours). 



It aids the clearing process to blot the sections on the slide, 

 add a drop or two of the clearing agent, pour it off after a 

 minute or two, blot again and repeat the process. 



The following clearing agents are also used: bergamot oil; 3 parts 

 white oil of thyme and 1 part of clove oil ; 3 parts of xylol and 1 part 

 of carbolic acid ; to this calcined copper sulphate may be added to 

 dehydrate it (it discolours certain aniline stains, and for such 

 Weigert substitutes aniline oil for the carbolic acid). 



Some specimens of origanum oil and of cajeput oil are said to 

 have a slight solvent action on celloidin. 



Equal parts of chloroform and absolute alcohol may be used 

 instead of 95 p.c. alcohol to dehydrate. 



Solvents for celloidin. A mixture of equal parts of ether and 

 absolute alcohol ; or either alone ; the former has a much greater 

 solvent power than the latter. 



Carvol (01. carvi). 



Clove oil and cedar-wood oil also dissolve celloidin, though 

 slowly. Clove oil should not be used for aniline dyes which are 

 soluble in it. 



Fixing sections to the slide. Of the various methods the 

 following may be mentioned. A thin layer of egg-albumin and 

 glycerine is spread upon the slide, which is then placed at 100 C. 

 for a few minutes to coagulate the albumin. The celloidin 

 sections from 70 p.c. alcohol are arranged on this. The alcohol 

 is then soaked up with blotting-paper, and the sections pressed 

 firmly with a pad of blotting-paper. 



L. 20 



