408 HISTOLOGY. 



in shallow boxes. Before being stained they must be attached to slides as 

 follows. 



To attach paraffin sections to a slide, a mixture of equal parts of glyc- 

 erine and white of egg is used, which may conveniently be called albumen. 

 Its two ingredients should be stirred together thoroughly and filtered, after 

 which a small lump of camphor is added as a preservative. It is kept in a 

 capped bottle with a glass rod for a dropper. A drop or two are placed 

 upon a clean slide and rubbed evenly with the finger over all that area upon 

 which sections may be placed. It should be free from bubbles and should 

 make a layer thick enough to allow the finger to glide easily over the surface 

 of the slide. Then a few drops of water are placed upon it, forming a layer 

 over the albumen deep enough to float the paraffin sections, strips of which 

 are placed upon the water. The shiny side of the ribbon should rest upon 

 the water. The slide is then held for a moment over the flame of an alcohol 

 lamp so that the water is heated and the sections become flat and smooth. 

 The paraffin must not be melted. This manipulation with a large slide 

 bearing several rows of serial sections, requires some skill; the water should 

 not come in contact with the fingers holding the slide and if the albumen 

 layer ends abruptly before reaching the border of the slide, the water will 

 not spread beyond it. Surface tension is such that enough water can be 

 put upon the slide to float the sections freely. After the flattening process 

 the water is cautiously drained off by a moist sponge held at the corner of the 

 slide. The sections settle down upon the albumen and may be arranged in 

 straight lines with needles applied to the paraffin but not to the sections 

 themselves. After this the slide is held vertically in contact with filter 

 paper to drain off any water which may remain. The slide is then placed in 

 a drying oven which is not warm enough to melt the paraffin. It is well to 

 let the sections remain there over night but a few hours may be sufficient to 

 dry them thoroughly. 



In preparing large numbers of slides, each bearing only one or two 

 paraffin sections, fragments of the ribbon containing the desired number 

 of sections are floated in a basin of water warm enough to flatten but not to 

 melt them. Slides rubbed with albumen are dipped into the water beneath 

 the sections which are held in place upon them with a needle. The slides 

 are drained and dried in the usual way. 



STAINING AND MOUNTING. 



The staining of paraffin sections is accomplished by placing the slides 

 to which the sections have been attached, in pairs back to back, in tube- 

 like vials containing stains. One should have a dozen such vials containing 

 various alcohols, xylol, stains, etc., the sections being passed from one to the 



