Embedding Tissues and Section-Cutting 137 



To Infiltrate a Tissue with Paraffin. — Dehydrate the 

 specimen in absolute alcohol for several hours, then transfer 

 to chloroform or xylol, in which it must remain until per- 

 fectly saturated. When clear, place in a bath of melted 

 paraffin of 45° C. (melting-point), and keep it at this tem- 

 perature for several hours, so that the paraffin may pene- 

 trate to the middle of the tissue. Then remove it from the 

 paraffin and put it into a small pill-box, pour in enough 

 paraffin to fill the box, and as the paraffin cools, add a little 

 more to make up the skrinkage and set aside to cool. 

 When cold, place in water for a few minutes ; this will soften 

 the paper, and facilitate the removal of the pill-box. You 

 will now have a cylinder of paraffin with the specimen 

 firmly fixed in its centre, and, if desired, the paraffin may 

 be pared away from the sides until a square block is 

 obtained. The sections may now be made by hand with a 

 razor, or the block can be fixed to a microtome with a little 

 melted paraffin. The sections must be placed in turpentine 

 to remove the paraffin, then in absolute alcohol to remove 

 the turpentine, and, finally, in distilled water to remove the 

 alcohol ; they may then be stained. Sometimes it is 

 desirable to stain the tissue in bulk before it is embedded. 

 In this case the sections need only go into turpentine or 

 benzole to wash away the paraffin ; they may then be 

 mounted in Canada balsam. 



The above process requires an embedding bath. This is 

 usually an expensive affair, but one that will answer all 

 ordinary purposes can easily be made. 



Get a small potato-steamer, and cut a hole in the lower 

 vessel to admit a spirit or small paraffin lamp. Get a tin- 

 smith to cut out a circular plate of tin to fit into the upper 

 vessel, in which some holes must be cut to take the test- 

 tubes, and to the sides of the vessel four small pieces of tin, 

 bent at right angles, must be soldered to support the tin 

 plate. A piece of tin must also be soldered over the per- 

 forated bottom of the vessel, so that it will hold water. 

 When the alterations are complete, place a layer of cotton- 



