298 NORMAL HISTOLOGY. 



folds and flatten the paper again. Next, make a transverse fold 11 

 inch from one end of the paper (folds 2-2, also partly represented 

 by C-D), and then fold in the corners so that the creases make angles 

 of 45 degrees with the edges of the paper (folds 3-C and 3-D). 

 When this has been done, make the fold 4 by turning down the free 

 edge of the paper so as to keep the corners in place. Treat the other 

 end of the paper in the same way. The folded edge 4 and its 

 counterpart (4) can now be drawn apart and, after a little manipula- 

 tion, the box will assume its final shape. This box is nearly filled 

 with melted paraffin kept fluid by placing the box on top of the 

 paraffin oven. The bits of tissue are placed in the paraffin with the 

 surfaces from which sections are to be made resting upon the bottom 

 of the box. The pieces of tissue should not touch the sides of the 

 box. During these manipulations the forceps should be kept warm 

 enough to keep the paraffin melted. When the tissues are in proper 

 position the box is floated on cold water, which rapidly chills the 

 paraffin. When cold, the paper can usually be readily stripped from 

 the block of paraffin. If there is any difficulty due to a softening 

 of the paper by water, drying will restore a sufficient firmness to the 

 paper. It is important that the paraffin should cool rapidly, and 

 that enough should be originally placed in the box more than to 

 cover the specimens completely, as some shrinkage takes place on 

 cooling. If more than one specimen is embedded in the same box, 

 they should be well separated from each other, so that irregular 

 cleavages of the paraffin when it is subdivided may not bring the 

 surfaces of the individual blocks too near the embedded specimen. 

 A little study of the method of folding paper to make boxes will 

 enable the reader to make a box of any desired dimensions. 



If the specimens to be embedded have previously been impreg- 

 nated with paraffin and then preserved on pieces of paper as described 

 above, any excess of paraffin upon the specimen may be removed 

 by placing it on a piece of filter-paper and warming it gently until 

 the superfluous paraffin is absorbed by the paper. The trimmed 

 surface is then laid upon a small glass plate that has been smeared 

 with a mere trace of glycerin, and metallic right-angles, similarly 

 smeared on the inside, are placed around the specimen in such a way 

 as to form a box with a clear space at least an eighth of an inch broad 

 between its sides and the specimen. Melted paraffin, at a temperature 

 only slightly exceeding that necessary to keep it fluid, is then poured 

 into the box, filling it. The paraffin should now be made to cool 



