CHAPTER VI. 67 



121. Cedar Oil (NEELSEN and SCHIEFFERDECKER, loc. cit., 118).- 

 Clears readily tissues in 95 per cent, alcohol without shrinkage ; does 

 not extract anilin colours. Celloidin sections are cleared in five to 

 six hours. 



The observer should be careful as to the quality of the cedar oil. 

 he obtains. I have examined the clearing properties of a sample, 

 obtained from a celebrated firm, which totally failed to clear absolute 

 alcohol objects after many days. 



Cedar oil is very penetrating, and for this and other reasons is, in 

 my experience, the very best of all media for preparing objects for 

 paraffin imbedding. I find it to be less hurtful to cells than any 

 other medium known to me. Tissues may remain in it for any 

 length of time without hurt. If it should become milky through 

 keeping, filter. 



122. Clove Oil. Samples of clove oil of very different shades of 

 colour are met with in commerce. It is frequently recommended 

 that only the paler sorts should be 'employed in histology. Doubt- 

 less it is, in general, best to use a pale oil, provided it be pure ; but 

 it is not always easy to obtain a light-coloured oil that is pure. 

 Clove oil passes very readily from yellow to brown with age, so that 

 in choosing a colourless sample you run great risk of obtaining an 

 adulterated sample, for clove oil is one of the most adulterated 

 substances in commerce. 



Clove oil does not easily spread itself over the surface of a slide, 

 but has a tendency to form very convex drops. This property makes 

 it a very convenient medium for making minute dissections in. It 

 also has the property of making tissues that have lain in it for some 

 time very brittle. This brittleness is also sometimes very helpful in 

 minute dissections. 



These qualities may be counteracted if desired by mixing the clove 

 oil with bergamot oil. 



This is one of the most useful of clearers. According to BEHRENS 

 (Tabellen, 3rd ed., 1898, p. 33), it will clear from alcohol of 74 per 

 cent. 



It has a high index of refraction, and clears objects more than 

 balsam mounting media. It dissolves celloidin (or collodion), and 

 therefore should not be used for clearing sections cut in that medium 

 without special precautions. New clove oil washes out basic tar 

 colours more quickly than old. 



123. Cinnamon (or Cassia) Oil greatly resembles clove oil, but is in 

 general thinner, and is more highly refractive. An excellent medium, 

 which I particularly recommend. 



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