82 CHAPTER VI. 



Clears readily tissues in 95 per cent, alcohol without shrink- 

 age ; does not extract auilin colours. Celloidin sections are 

 cleared in five to six hours. 



Cheap, but requires an inconvenient length of time for 

 the clearing of celloidin sections. 



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 the celebrated firm of Kousseau, 

 Paris. This sample was absolutely colourless. It 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 and delicate tissue-structures than any 

 other medium known to me. 



110- 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. A word of explanation is here necessary. 

 Doubtless 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 colour- 

 less sample you run great risk of obtaining an adulterated 

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

 stances in commerce. 



Two important properties of clove oil should be noticed 

 here. It 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. The second property I wish to call 

 attention to is that 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. 



Clove oil ha,s a high index of refraction, and clears ob- 

 jects more than balsam mounting media. It dissolves cel- 

 loidin (or collodion), and therefore should not be used for 

 clearing sections cut in that medium, without special pre- 



