2 9 S PARAFFIN METHOD [ CH. X 



In the winter it is a good plan to warm the microtome and sec- 

 tion knife before sectioning. This can be very easily done by put- 

 ting a cloth over the radiator and the microtome something like a 

 tent. 



| 445. Electrification of the Paraffin Ribbons. Some days there is such 

 an accumulation of static electricity in cutting the ribbons that they jump 

 toward anything brought near them. This is very annoying and liable to be 

 so destructive to many of the sections that serial work (| 472) can not be done 

 with safety. 



Many devices have been tried to overcome this difficulty, like burning a 

 gas jet near the microtome, boiling water near the apparatus etc. , but the safest 

 way is to wait for more favorable conditions. 



To overcome this electrification, Dixon, (Jour. Roy. Micr. Soc., 1904, p. 

 590), recommends fastening a 5 milligram tube of radium bromide on the 

 knife near where the sectioning is done. The radium ionizes the air and ren- 

 ders it a good conductor, and then the static electricity cannot accumulate. I 

 have not been able to try this method. 



| 446. Storing Paraffin Ribbons. The most convenient method for caring 

 for the ribbons as they are cut is to place them on a tray (Fig. 212) lined with 

 a sheet of white paper. It is important to write on the paper full data, giving 

 the name of the tissue, the thickness of the sections, the date etc. It is well 

 also to number the ribbons and to indicate clearly the position of the first 

 section or the beginning of the ribbon. 



Ribbons of sections on a tray should be covered by another tray if one 

 wishes to carry them to another room. The slightest gust of air sends them 



flying- 

 Ribbons on trays may be kept a long time, three or four years at least, if 

 they are stored in a cool place. The sections do not flatten out quite as well 

 after standing a long time as they do soon after they are made. 



447. Spreading the Sections. Paraffin sections are almost 

 invariably slightly wrinkled or folded in cutting. To remove the 

 wrinkles one takes advantage of the expansion of paraffin when it is 

 warmed. The sections may be floated on warm water when they 

 will straighten out and become smooth, or the usual method is to 

 'stretch them on the slide upon which they are to be finally mounted. 



448. Spreading Sections on a Slide. A double operation 

 is performed in this way, viz; the sections are made smooth and they 

 are also fastened to the slide. Put a minute drop of albumen fixi- 

 tive on the middle of a slide (Fig. 187) and with the ball of one fin- 

 ger spread it over the slide, making a thin even layer. It cannot be 

 too thin. It is liable to stain if it is too thick. 



