Mounting 



PARAFFIN SECTIONS 



125 



Canada balsam is so conventional that it 

 may be taken as an example. The shde is 

 removed from the xylene and drained (Fig. 

 78) and then placed on any convenient 

 flat surface. A drop of the mountant is 

 then placed on the surface of the sections. 

 A covershp of suitable size (Fig. 79) is 

 then held at an incUned angle with a bent 

 needle and slowly lowered so as to exclude 

 all air bubbles. The edges of the slide are 

 then roughly wiped and it is returned to 

 the hot table shown in Fig. 78 to evapo- 

 rate the solvent used for the resin. Though 



This custom of evaporating the solvents 

 from the surface of the sUde rather than 

 from the edge of the coverslip is nowadays 

 considered old-fashioned; but there is no 

 doubt that it produces a better and more 

 durable slide than does the more usual 

 procedure. 



One very common accident, which maj'' 

 occur in the course of staining or dewaxing 

 a slide, is that the individual sections show 

 signs of l)ecoming detached, either through 

 not having been perfectly in contact with 

 the shde when dried, or through having 



Fig. 79. Placing the coverslip on serial section slide. 



this is the conventional method of opera- 

 tion it is by no means always the best. In 

 particular there is a tendency to ha\'e a 

 higher concentration of solvent along the 

 edges of the coverslip than in the center, 

 and it also takes a surprisingly long time for 

 the whole of the solvent to be removed. It 

 is much bettei', if one can si)are the time, 

 to place a relatively thin coat of mounting 

 medium on top of the slide and then to 

 leave the solvent to evaporate from this on 

 the surface of a hot plate. There is no risk 

 that the slide will dry out, for the mount- 

 ant will act as a varnish. On the next day 

 the slide is examined and, if it appears to 

 be sufficiently varnished, the coverslip is 

 placed on the surface and warmed while 

 maintaining steady pressure. The slide 

 will then be hardened as soon as it is 

 cooled and may be cleaned and put away. 



been exposed to some reagent which has a 

 solvent action on the adhesive. The effects 

 of this unfortunate accident may be mini- 

 mized by having always on hand a coplin 

 jar of the solution of Claoue 1920 (Chap- 

 ter 28, V 21.1). This is a most admirable 

 lacquer into which the slide may be dipped 

 rapidly and withdrawn. This transparent 

 lacquer hardens readily in place and holds 

 the section attached without seriously 

 interfering with subsequent observation. 



Cleaning and Labeling Slides 



No slide can be considered complete un- 

 til it has been properly labeled, cleaned, 

 and stored. Failure to clean a shde can 

 cause rather serious damage for, if un- 

 wanted portions of Canada balsam are 

 left lying about close to the edges or on 

 the surface, and if the slide be then used 



