1 66 PARAFFIN SECTIONING. iCH. VII. 



the tissue must remain longer in the warm chamber. If the chloro- 

 form has all evaporated, melt some pure paraffin (that designated 

 " hard paraffin " by the dealers is usually about the right hardness). 



Make a little paper box, fill it half full of the pure melted paraffin 

 and then arrange the tissue in it so that sections may be made across 

 the short axis. Put the tissue near one end of the box, and as soon as 

 the paraffin has solidified on the surface place the box in cold water so 

 that it will cool quickly. 



§ 274. Cutting the Sections. — After the imbedding mass is well 

 cooled, remove the paper box and trim the end in which the tissue is, 

 in a pyramidal form. Clamp the block of paraffin into the microtome 

 so that the tissue will be at about the level of the top of the microtome. 

 With a very sharp razor cut the sections. The razor should be dry, 

 and the sections are made with a rapid, straight cut as in planing. Do 

 not try to section with a drawing cut as with collodion sectioning. If 

 the temperature is right for the paraffin the sections will remain flat, 

 and if the end is pyramidal successive sections will adhere and thus 

 make ribbons. If the paraffin is too cold the sections will roll. In 

 that case place the microtome near the steam pipes a little while. 

 Remember that sections must be from 5/* to 15/* thick to show well. 

 Sections of that thinness cannot be made with a dull razor nor of an 

 object too large. 



§ 275. Fastening the Sections to the Slide. — To fasten the sec- 

 tions to the slide, coat the center of the slide, or the whole if a series is 

 to be made, with the Albumen Fixative (§ 293). Do this by adding a 

 little of the fixative and then with a clean finger rub the albumen over 

 the slide and beat or tap the slide with the finger. This will make 

 a very thin and even layer. Place the sections in position and press 

 them to the slide with the finger. Then spread over them a small 

 amount of a ^th% collodion (§ 304). Allow them to dry in the 

 air for 2 to 10 minutes. 



§ 276. Removing the Paraffin. — Immerse the slide in a vessel of 

 xylene or benzin. This will dissolve the paraffin. Half an hour will 

 usually suffice. One can hasten the solution by moving the slide in the 

 benzin. In this way it may be dissolved in 3 to 5 minutes. It will do 

 no harm to leave the slide in the benzin or xylene over night. Two or 

 three days might not do any harm, but it is usually better to proceed 

 at once to the other operations. 



§ 277. Removing the Benzin. — From the benzin or xylene plunge 

 the slide bearing the sections into a jar of 95 # alcohol and leave it for 

 a few minutes or move it around for a half minute or so. 



