Staining 



PARAFFIN SECTIONS 



119 



ing it to fall off or at least making it 

 very difficult to observe jwoperly when 

 mounted. There is also the risk in this 

 procedure that the water will not stop at 

 the edge of the shde, but will unexpectedly 

 flood off, (;arrying the sections with it onto 

 the surface of the hot plate. 



Another procedure, frequently used by 

 the author but not recommended for the 

 inexperienced, is to blot the sections be- 

 fore putting them on the hot plate. A 

 water-saturated piece of coarse filter paper 



appearance, cause, and cure of the more 

 conunon defects are shown in the pages 

 which follow. These are by no means the 

 only defects or the only cures which may 

 be api^lied. Every user of the microtome 

 should have in his hands a copy of Rich- 

 ards 1949, which lists many suggestions 

 beyond those here given. 



Staining and Mounting Sections 



Assuming that all difficulties have been 

 overcome, and tliat one now has a series of 



i_j._^ ' .-J... i i J-i~i 



Fig. 70. Warming tlie flooded ribbons in order to flatten them. 



is placed on the drained slide and pressed 

 hard with a rubber roller, which squeezes 

 much of the water out of both the paper 

 and the sections. This makes sure that the 

 sections are perfectly flattened in contact 

 with the slide, but requires a strong nerve 

 to try for the first time, because most 

 people fear that the sections will stick to 

 the paper. This has never happened in a 

 good many thousands of shdes which the 

 author has made by this means. Shdes so 

 prepared are always free of air bubbles. 



Before proceeding to a discussion of the 

 next steps to be taken, it may be as well 

 to revert to the moment when section 

 cutting started, and to discuss the innum- 

 erable things that may happen, other than 

 the production of a perfect ribbon. The 



shdes bearing consecutive ribbons, the 

 paraffin must next be removed in order 

 that the sections may be stained. It is con- 

 ventional, though probably not necessary, 

 to warm each sUde over a flame (holding it 

 as shown in Fig. 70) until the paraffin is 

 molten. The shde is then dropped (as 

 shown in Fig. 78) into a jar containing 

 xylene, benzene, or some other suitable 

 paraffin solvent. The jars shown in this 

 figure are of the type known as coplin jars, 

 which are usually employed when a rela- 

 tively small number of 1" X 3" shdes are 

 to be handled. Larger numbers of small 

 slides are more conveniently handled by 

 being placed in racks, which may be 

 moved from one rectangular jar to an- 

 other. Individual slides may, of course, be 



