126 NATURALISl-S' ASSISTANT. 



It will be seen that in the above hardening processes the 

 specimen was left in strong alcohol. This fits it for the next 

 step, which is to soak it for a while (say half an hour) in spirits 

 of turpentine. While the specimen is soaking the paraffine 

 should be melted in a water bath (or in its absence a sand 

 bath may suffice), over a spirit lamp or gas jet. A small por- 

 tion of the paraffine should always be allowed to remain un- 

 melted as thus the remainder will not acquire too high a 

 temperature. When melted a portion of the paraffine is 

 poured into a paper tray covering the bottom to the depth of 

 an inch, and just allowed to " set.'' The object is then re- 

 moved from the turpentine, the superfluous spirit being re- 

 moved by blotting paper, and next placed on the surface of 

 the paraffine in the tray and completely covered by more of 

 the melted paraffine. When cold it is ready for cutting. The 

 object when placed in the tray should be in such a position 

 that the sections may be cut in the desired plane, and note 

 should be taken of its position, as after the paraffine becomes 

 hard this is difficult to ascertain. 



In case the specimen to be embedded contains cavities, 

 pains should be taken to fill these with paraffine. The usual 

 method of doing this is to transfer the object directly from 

 the turpentine to a mixture of half turpentine and half par- 

 affine which is kept just melted. After a few minutes' immer- 

 sion in this mixture it is transferred to the tray and the process 

 completed as before. 



A convenient tray may be made from common writing paper 

 by taking a piece of proper proportions to the object to be 

 embedded, longer than wide and folded on the lines shown in 



