APPENDIX 155 



Cedar-wood oil, clove oil, creosote, xylol and benzol are some 

 of the common fluids used for this purpose. Not only do 

 they remove the alcohol but they also render the object 

 transparent and are therefore called clearing agents. Cedar- 

 wood oil and xylol are the most commonly used of the oils 

 mentioned. When the object has become transparent it 

 is placed on a slide, the excess of oil allowed to run off, or 

 removed with filter paper, then a drop of Canada balsam 

 placed on the object and this is covered with a thin cover 

 glass which is allowed to gently settle on the object. When 

 the balsam has hardened the object is permanently fixed. 

 If -absolute alcohol is not at hand for the final dehydration, 

 place the object from 95 per cent alcohol directly into a 

 mixture of one-third beechwood creosote and two-thirds 

 xylol, or into the same proportions of xylol and melted car- 

 bolic acid crystals. Cedar oil and oil of cloves will also clear 

 directly from 95 per cent alcohol. After the object has 

 been cleared proceed as directed in the previous paragraph. 

 Before a slide is laid away it should be labeled as to the 

 animal, or part, or tissue; how fixed; how stained; date 

 and name of person making the preparation. 



Reagents. 



Acetic Acid. A solution of 0.2 per cent to 1 per cent 

 applied to fresh tissues will render the nuclei visible. % 



Alcohol. This is the most used reagent in the laboratory 

 and should be kept on hand in abundance, made up in 

 various strengths. Alcohol is rather expensive if bought in 

 small amounts from a druggist or ordinary dealer, but it 

 can be purchased, for scientific purposes, with the revenue 

 tax remitted. The collector of internal revenue of the 

 district, or the Federal Treasury Department can give 



