36 ' Paraffin Method (chap. 3) 



tissues (lung) and eliminate holes in the final paraffin block. [Weiner, 

 1957; Luna and Ballon, 1959) 



Embedding with Paraffin 



As soon as the tissue is thoroughly infiltrated with paraffin, it is ready 

 to be embedded; the paraffin is allowed to solidify around and within 

 the tissue. The tissue is placed in a small container or paper box 

 already filled with melted paraffin and the whole is cooled rapidly in 

 water. Before transferring the tissue, warm the instruments which 

 manipulate it. This will prevent congealing of paraffin on metal sur- 

 faces. Handle the tissue and paraffin as rapidly as possible to prevent 

 the paraffin from solidifying before the tissue is oriented in it. Orienta- 

 tion is important. If the tissue is placed in a known position and care- 

 fully marked with a slip of paper in the hardening paraffin (Fig. 9), it 

 remains a simple matter to determine the proper surface for sectioning. 

 If a paper box is used, the orienting mark may be made directly on one 

 of its flaps. 



Each technician eventually adopts his or her own pet embedding 

 mold or container. A few suggestions: petri dishes, Syracuse watch 

 glasses, shallow stender dishes, test tubes to concentrate solid contents 

 of tissue or body fluids, and a neat little dish for tiny pieces — perhaps a 

 miniature Syracuse watch glass (watch glasses, U.S. Bureau of Plant 

 Industry Model, 20 mm. inside diameter, 8 mm. deep, A. H. Thomas 

 Co., #9850). Lightly coat the insides of glass dishes with glycerol; then 

 the solidified paraffin block loosens readily. Cast lead L s (Lips haw 

 #334, Diamond embedding boxes) when placed on a small flat metal 

 rectangle can be adjusted to almost any size for embedding, and, being 

 metal, they cool the paraffin more quickly than glass. Also they break 

 loose immediately from the paraffin. Lipshaw also has a Pop-out Em- 

 bedding Mold. 



Paper boxes may be fashioned according to Figs. 1, 2, 3. Perhaps the 

 one advantage of these is that they and any data recorded on them can 

 be left permanently on blocks which have to be stored. The Lipshaw 

 Company offers a disposable mold, called the Peel-A-Way Disposable 

 Embedding Mold. These molds are made of lightweight plastic, avail- 

 able in five sizes, and are easily broken at the corners so the sides can be 

 peeled down and the moll pulled away. Perforated tabs to fit can be 

 purchased. Various devices such as refrigerator trays with their dividers 

 can be used for embedding a number of large pieces of tissue. Lipshaw 



