124 



THE ART OF MAKING MICROSCOPE SLIDES 



Staining 



hoi and xylene, to make sure that the 

 whole of the wax is removed. If even a 

 small trace of wax remains, it will prevent 

 the penetration of stains. Assuming that 

 one is proceeding along tlie classic xylene- 

 alcohol series, the shde is transferred from 

 either the fresh xylene or the xylene-abso- 

 lute-alcohol mixture, to a coplin jar of ab- 

 solute alcohol. It is unfortunate that no- 

 body seems yet to have placed on the 

 market a coplin jar, or slide-staining dish, 

 the lid of which is satisfactorily ground 

 into position so that absolute alcohol, 



soon, however, as the slide has been in 

 water long enough to remove the alcohol, 

 it should be withdrawn and examined 

 carefully to make sure that it has been 

 sufficiently dewaxed. If the water flows 

 freely over the whole surface, including 

 the sections, it is safe to proceed to stain- 

 ing by what ever manner is desired. If, 

 however, the sections appear to repel the 

 water, or if tliere is even a meniscus 

 formed round the edge of the section, it is 

 an indication that the wax has not been 

 removed, and that the slide must again be 



Fig. 78. Starting a slide tlirougli the reagent series. 



which is very hygroscopic, remains uncon- 

 taminated. It does not matter if xylene is 

 carried over into the absolute alcohol, but 

 as soon as the first trace of a white floc- 

 culent precipitate appears in the alcohol — 

 indicating that some wax is being carried 

 over — the alcohol must be replaced. 



The writer never l)others to use a series 

 of graded alcohols between absolute al- 

 cohol and water. These graded series are 

 necessary, of course, when one is dealing 

 with the dehydration of whole objects 

 which may be distorted, l)ut the author 

 has never been able to find the slightest 

 difference between thin sections which 

 have been passed from absolute alcohol to 

 water, and those which have laboriously 

 been downgraded through a series. As 



dehydrated in absolute alcohol, passed 

 back into a xylene-alcohol mixture, and 

 thence again into pure xylene. 



In the specific examples which conclude 

 this chapter, and in numerous places 

 throughout Chapters 20, 21, and 23, de- 

 scriptions are given of indi\'idual staining 

 methods. The purpose of this chapter is to 

 discuss only the general principles in- 

 volved in the preparation of paraffin sec- 

 tions, so that we may presume the section 

 to have been already stained and returned 

 (through such dehj'drants as are specified 

 in the method used) to xylene, and to be 

 ready for mounting. 



It is again assumed that the section will 

 be mounted in one of the resinous media 

 described in Chapter 26 (M 30), and 



