PERMANENT MOUNTING 51 



All the above methods involve the partial or complete 

 disorganization of the protoplasmic body : the following 

 method of treatment has the advantage of preserving 

 the structure of the protoplasm and of the nucleus, and 

 it is specially applicable to material in which the proto- 

 plasm has been fixed by alcohol, or by picric acid and 

 alcohol. The sections (after staining, if that is con- 

 sidered necessary) should be placed for a few minutes 

 in absolute alcohol ; they should then be transferred to 

 a watch-glass, containing either a mixture of turpentine 

 and creosote (four parts of the former to one of the 

 latter), or some oil of cloves ; sections which have been 

 stained with aniline dyes are best cleared by cedar- 

 wood oil ; they should be left in this for a short time, 

 until they appear to be quite transparent, and should then 

 be mounted in a drop of Canada balsam or Dammar. 



Oil of cajeput will do instead of oil of cloves, and is 

 cheaper, but not altogether satisfactory. 



Permanent Mounting. It was pointed out in the 

 previous chapter that objects mounted in water cannot 

 easily be kept, while the objects do not appear so trans- 

 parent in water as in some medium of higher refractive 

 index. The media most commonly used are glycerine, 

 glycerine jelly, Canada balsam, and Dammar. 



Glycerine. This may be used for objects prepared 

 from fresh ^material, or hardened with alcohol, &c., and 

 is especially suited to objects stained with ammomacal 

 solution of hsematoxylin, carmine, and many of the 

 aniline colours: it is also used for objects cleared by 

 potash, calcium chloride, or " eau de javelle." Dilute 

 glycerine should be used for this purpose, consisting of 

 a mixture of pure glycerine with an equal bulk of water. 



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