Making Sections 135 



with the aid of two thick L-shaped pieces of metal which, when fitted 

 together, form a rectangular mold of varying dimensions. The author re- 

 gards these as very clumsy and would always prefer to prepare a card- 

 board or paper box rather than to endeavor to maneuver metal molds 

 which are always getting jarred out of place at the wrong moment. The 

 preparation of a paper box is easy; the method preferred by the author is 

 shown in Figs. 93 to 99. 



After the box has been prepared, the actual process of embedding is 

 begun. This is shown in great detail in Figs. 100 to 103. Before starting, 

 it is necessary to provide the following items: (1) a dish of water of 

 sufficient size that the finished block may be immersed in it readily; in the 

 illustration an ordinary laboratory finger bowl is in use, (2) some form 

 of heat, an alcohol lamp being just as effective as a bunsen burner, (3) a 

 large slab of plate glass, and (4) a wide-mouthed, eye-dropper type of 

 pipette. The oven employed should contain the object itself in a small 

 container of molten wax, as well as another container of the medium 

 used. It must be emphasized that one cannot impregnate an object with 

 one kind of wax and embed it in another. The first thing to do is to wet the 

 underside of the bottom of the paper box in the water and press it firmly 

 into contact with the plate-glass slab, which will both hold it in position 

 and assist in cooling the wax. Then take (Fig. 100) one of the beakers 

 of molten embedding material from the oven and fill the little paper box 

 to the brim. Heat the pipette in the flame to a temperature well above 

 that at which the wax will melt. Use it to pick up the object from its own 

 dish (Fig. 101) and to transfer it to the paper box. By the time that this 

 has been done, a layer of hardened wax will have been formed at the 

 bottom of the paper box, so that the object will rest on the layer of solidi- 

 fied wax with a molten layer above it. It will happen almost invariably 

 that the surface has also cooled, so that a crust of cool wax will have been 

 carried down with the object into the box. It is essential to get rid of 

 this if the wax is to adhere through section cutting. Reheat the pipette; 

 use it to melt the entire surface of the box (Fig. 102) and to maneuver 

 the object into the approximate position in which it is required to lie in 

 the finished block. Then blow on the surface until the wax is sufficiently 

 solidified to enable you to pick up the box carefully and, as shown in 

 Fig. 103, hold it on the surface of the water used for cooling. With most 

 wax media it is desirable to cool the block as rapidly as possible, and it 

 should never be permitted to cool in air. It cannot, however, be pushed 

 under the surface of the water because the molten center is liable to break 

 through the surface crust and thus destroy the block. After holding the 

 box in the position indicated until it is fairly firm throughout, push it 

 under the surface to complete the cooling. Large blocks should be kept 

 under the surface with weights. 



