PARAFFIN SECTIONS 109 



section is known to be cleared when it appears quite 

 transparent and almost invisible when the watch-glass 

 or capsule containing it is held over a dark surface. If 

 after two minutes in the clearing agent the section still 

 appears cloudy and opaque, it has not been sufficiently 

 dehydrated, and should be returned to a fresh bath of 

 absolute alcohol for a short time, and then transferred 

 again to the clearing agent. Care should be taken that 

 watch-glasses, etc., used for the absolute alcohol and 

 clearing agent are perfectly dry. The clearing agent, 

 especially clove oil, can be used many times before 

 becoming useless. 



For transferring the sections from one solution to 

 another an ordinary needle, fixed in a light wooden handle, 

 suffices, or, better still, a piece of glass drawn out at one 

 end, the section being carefully lifted by one corner to 

 prevent crumpling ; but for the final process of mounting 

 it is necessary to use a section lifter or cigarette-paper. 

 The section, spread out with care, is raised by means of 

 the section lifter or cigarette-paper introduced under it, 

 and transferred to the slide, any crinkles are removed 

 by spreading with a needle, the superfluous clearing agent 

 is drained off, a drop of xylol balsam put on, and it is then 

 covered with a clean cover-glass. If clove oil has been used 

 as the clearing agent, the section, after draining, should 

 be blotted with two or three thicknesses of filter-paper 

 to remove as much oil as possible before putting on the 

 balsam. In blotting firm pressure should be used, and 

 the section will then adhere to the glass slide and not to 

 the blotting-paper. With delicate sections all the pro- 

 cesses of staining, dehydrating, clearing, etc., may be 

 carried out on the slide. 



(b) Paraffin sections. The section fixed on the slide 

 (p. 93) must be freed from paraffin before staining and 

 mounting. The slides with attached sections are treated 



