CHOICE AND USE OF APPARATUS 



method of doing so varies somewhat with the 

 nature of our object and to describe all the methods 

 of mounting microscopic objects permanently would 

 require a book in itself. We will suppose that we 

 wish to make a permanent slide of one of the 

 sections floating in our watch glass of water. The 

 first thing we must do is to get rid of the water 

 with which our section by now is saturated. This 

 may be accomplished by means of alcohol of various 

 strengths, which we may put into three watch 

 glasses. In the first watch glass we have half pure 

 alcohol and half water; in the second three- 

 quarters alcohol and one part water; in the third 

 watch glass pure or absolute alcohol. The section 

 is transferred on a brush to the first watch glass 

 and left there for five minutes, then to the second 

 watch glass for a similar time and finally to the 

 third watch glass. The mountant may be either 

 Canada Balsam or glycerine jelly. Should we 

 decide on Canada Balsam, we put a small drop of 

 the substance in the centre of a clean slide, place 

 one section atop of it and then gently lower a cover 

 slip upon it as already described. Then, without 

 using any force, the cover slip is pressed down, but 

 we must not fall into the all too common error of 

 thinking that a thick section can be made thin by 

 pressing upon the cover slip. If we have taken the 

 correct amount of Canada Balsam it will just cover 

 the area below the cover slip and no more, if we 

 have used too much, it wdll flow out on all sides 

 and perhaps on the top of the cover slip. A very 



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