/)/| PRACTICAL HISTOLOGY. 



The method of interstitial embedding is particularly useful for 

 tissues stained "in balk" or en masse. The tissues or organ may 

 be stained before the process is begun, or sections may be cut and 

 stained afterwards. 



To Stain "in bulk" before embedding. Pieces of the tissue a 

 few millimetres square are placed in borax-carmine or Kleinen- 

 berg's logwood for 10-24 or 48 hours, according to the size and 

 nature of the tissue. If they be placed in borax-carmine, the pieces 

 are transferred to acid alcohol for 24 hours, and then transferred to 

 various strengths of alcohol, and finally to absolute alcohol, by 

 which they are completely dehydrated. The tissues stained with 

 Kleinenberg's logwood are well washed in spirit, and transferred 

 to absolute alcohol to be dehydrated. These dehydrated stained 

 masses are then placed in turpentine or xylol, and then in melted 

 paraffin, as described above. 



Process of Embedding in Paraffin. This is the same both for 

 the simple and the saturation methods. Use embedding |_'s, which 

 consist of two L-shaped pieces of lead about \ inch high, the long 

 arm about 2 inches long and the short 

 one |- inch. Their inner surfaces are 

 moistened with glycerine, and the L's 



themselves are placed on a piece of glass, coated with glycerine, to 

 enable the paraffin to separate easily, with the long limb of the 

 one in contact with the short limb of the other, thus making a 

 rectangular box, the size of which can be increased as required. 

 Fill the trough with melted paraffin. 



Take the tissue if for simple embedding direct from alcohol ; 

 dry its surfaces with bibulous paper, to remove any alcohol which 

 would prevent the paraffin from adhering to it; pour the melted 

 paraffin into the trough, transfix the tissue with a fine pin, plunge 

 it into the paraffin just when the latter begins to set at the edges, 

 move the tissue in the still fluid paraffin to one end of the trough, 

 and hold it there until the mass sets around it. 



If the tissue has been previously saturated with paraffin, the 

 trough is filled as before, and the tissue, saturated with paraffin, is 

 taken, by means of a hot needle, from the fluid warm paraffin, and 

 fixed in the trough in the same way as described above. It is not 

 always necessary to transfix the tissue with a pin or needle, but it 

 is' sometimes convenient to do so. Insert the needle in the 

 direction of the cutting plane, thus indicating afterwards (when 

 the mass is set) the direction in which the section is to be cut. A 

 little paraffin may be poured into the trough, and when it just 

 begins to set, the tissue is laid on it, and another layer of melted 

 paraffin is poured over it as soon as its surfaces are set. Place the 

 whole under the tap, and allow cold water to run over it to 



