PARAFFIN EMBEDDING 213 



The tissue should be placed in the mixture in a well-stoppered bottle and 

 be kept in the warm incubator (37-38 C.) for from 1-6 hours according to 

 the thickness of the block. 



4. After passing through the xylol-paraffin bath transfer to an open flask 

 or tube containing paraffin melting at 50 C. and heated to 52-53 C. (the 



FIG. 156. Paraffin oven. 



temperature must never reach 55 C.) in a paraffin oven (fig. 156) for -4 

 hours according to the thickness of the tissue. 



Very thin pieces, - 30 minutes. 



Thin pieces, - 1-2 hours. 



Medium-sized pieces, ....... 2-3 



Thick pieces, 3-5 



5. The tissue is now ready to be embedded. Melt some paraffin (melting 

 point 50, 52 or 55 C.) in a porcelain capsule. (For sections for bacterio- 

 logical examination paraffin melting at 52 C. is, generally speaking, the 

 best, but if the weather is very warm paraffin melting at 55 C. may be 

 preferred.) After the paraffin has been melted allow it to cool until a pellicle 

 forms on the surface. 



While the paraffin is melting select a mould and cover the bottom with a 

 thin layer of the melted paraffin, and as soon as it has begun to set (a few 

 seconds is sufficient) place the tissue, which may be conveniently held with a 

 lightly heated needle, on the surface, taking care that it is placed in a good 

 position and suitably orientated ; then fill up the mould with melted paraffin, 



