42 Animal Micrology 



(see step 10, chap. vi). With a clean finger, rub off all of the 

 fixative that can be easily removed so that only a very thin film 

 remains. 



18. Flood the slide with a few drops of distilled water until 

 the entire surface bearing the fixative is covered by a thin layer 

 of water, but do not put on sufficient to overflow the edge. 



19. Take up the first strip of paraffin ribbon with a brush or 

 needle and float it onto the surface of the water. The first sec- 

 tion of the series should be in the upper left-hand corner, but 

 back at least 5 mm. from the end of the slide. In case the label 

 is to be placed on the left end of the slide, allowance must be 

 made for it, of course. Add the successive strips of the ribbon in 

 the order of the lines of a printed page until as many rows are in 

 place as will conveniently lie under the cover, allowing for the 

 proper margins. See that each section presents the same aspect 

 to the observer as its predecessor (see 10, c). 



20. Warm the slide gently by holding it well above a small 

 flame until the paraffin flattens out and becomes free from wrinkles. 

 Be careful not to melt the paraffin, for heat sufficient to do so will 

 render the albumen useless. It is safer to heat the slide by 

 placing it upon the warm paraffin oven for a few min utes, instead 

 of holding it above a flame. 



21. Drain off the excess of water and set the slide away to dry 

 after properly numbering it with your glass-marking pencil. As 

 the water evaporates the sections are drawn down tightly into the 

 film of fixative. The slide is seldom sufficiently dried under six 

 hours. It is well to leave it twelve hours ; it may be left indefi- 

 nitely. The time may be shortened by placing a few thicknesses 

 of blotting paper under the slide and drying it on the paraffin 

 oven. Unless the slide is perfectly dry the sections will float off 

 during subsequent treatment. Take precautions to prevent par- 

 ticles of dirt from settling upon the surface of the sections. This 

 is usually accomplished by placing the slides upon some kind of a 

 rack and covering them with a bell-jar. Prepare several other 

 slides in the same manner as the above if sufficient of the ribbon 

 remains. 



