PARAFFIN SECTIONS 497 



a preservative. The mixture is kept in a glass-capped bottle, with a 

 glass rod for a dropper. 



A drop is placed upon a thoroughly clean slide and rubbed evenly 

 with the finger (freed from oil) over all the area upon which sections may 

 be placed. It should be free from bubbles and should make a very thin 

 layer, just thick enough to allow the finger to glide easily over the surface 

 of the slide. 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 alco- 

 hol lamp so that the water is heated. Repeat until the sections become 

 perfectly smooth and flat, but the paraffin must not be melted. The water 

 should not come in contact with the fingers holding the slide. If the al- 

 bumen layer ends abruptly before reaching the border of the slide, the 

 water will not so readily spread beyond it. 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 tissues of the sections. The slide is then held vertically in contact with 

 filter paper to drain off any water which may remain, and the portions 

 of the slide which are free from sections are wiped off with a cloth free 

 from lint. The slide is next placed in a drying oven which is not warm 

 enough to melt the paraffin. It is well to let the slides remain 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 sec- 

 tions, 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 with a needle. The slides are drained 

 and dried in the usual way, care being taken to have the sections in the 

 center of the slide. Or the ribbons may be floated on warm water and 

 cut into fragments with a heated knife, proceeding then as before. 



To remove the paraffin, the slides are immersed in xylol for about 5 

 minutes. The slide is then transferred in turn to a mixture of equal parts 

 of xylol and absolute alcohol, then through absolute, 95 per cent., 80 per 

 cent., 70 per cent, and 50 per cent, alcohols, remaining about i minute 

 in each, to water. In case the stain is in alcoholic solution, the transfers 

 may be stopped at that grade of alcohol which corresponds to the solvent 

 of the stain. 



In case the sectioned tissue was fixed in a fluid containing corrosive 

 sublimate and has not previously been treated with iodine for the removal 

 of mercurial deposits, enough tincture of iodine to give a port-wine color 



may be added to the 80 per cent, alcohol. The slide is immersed in this 



32 



