Ch. XI] PREPARATIONS BY THE PARAFFIN METHOD 



377 



days, depending on the size and character of the piece to be imbedded. 

 If the tissue was thoroughly dehydrated and well saturated with cedar 

 oil, the melted paraffin permeates the whole piece. 



§ 612. Imbedding in paraffin wax. — When the object is thoroughly 

 infiltrated imbed as follows: Make of strong writing paper a box 

 considerably larger than the piece to be imbedded. Nearly fill the 

 box with paraffin wax, place on a copper heater (fig. 226), and allow 

 to remain until bubbles appear in it. 

 Put the box on cold water until a thin 

 stratum of paraffin solidifies on the bot- 

 tom. Take the piece of tissue from 

 the infiltrating dish (fig. 220) and ar- 

 range in the box for making sections 

 in a definite direction. Add hot par- 

 affin, if necessary, and then place the 

 box on cold water. The more rapid 

 the cooling, the more homogeneous will 

 be the block containing the tissue to 

 be cut. For the best imbedding it is 

 well to drop 95 % alcohol on the sur- 

 face as soon as a film has formed in 

 cooling. In warm climates where cold 

 water is not easy to procure for cooling 

 the blocks, one may float the paper box 

 on 95 % alcohol and with a pipette (fig. 234) drop strong alcohol on 

 the sides of the box and on the top of the paraffin as soon as a sur- 

 face film has formed. 



It is very desirable to mark on the box the name of the imbedded 

 object and to indicate which end or face is to be cut (see also §657). 



§ 613. Fastening the block to a holder. — Use one of the block 

 holders or object discs furnished with the microtome, or a short 

 stove bolt (fig. 222). Heat the larger end and press the paraffin 

 block against the hot metal until it melts the paraffin. Hold the two 

 together while cold water Hows over them. When cold the block 

 is firmly cemented to the holder. Pains should be taken to have the 

 axis of the block parallel with the long axis of the holder; and one 



Fig. 220. Electric Infiltrat- 

 ing Box and Spreading Plate. 



(From the Anatomical Record). 



A The box with a metal 

 spreading plate on top. 



r Porcelain receptacle, i por- 

 celain insulation where the cable 

 (c) traverses the wall of the box. 



B Base or tray holding the in- 

 filtrating dishes and the beaker 

 for melted paraffin. 



