98 



THE ART OF MAKING MICROSCOPE SLIDES 



Embedding 



materially from those used in the prepara- 

 tion of wholemounts which have been de- 

 scribed in Chapter 6. The whole process 

 could, however, be much simplified if 

 people would only remember that water 

 is heavier than the majority of dehydrat- 

 ing agents, and that the majority of de- 

 hydrating agents are lighter than most 



The first prerequisite is some device 

 which will maintain wax just at its melt- 

 ing point. Most people employ complex 

 thermostatically controlled ovens for this 

 purpose, but the exceedingly simple device 

 shown in Fig. 37 has a great deal to recom- 

 mend it. As will be seen, this consists 

 essentially of a series of incandescent elec- 



i.'-,te 



Fig. 37. Simple radiant heat embedding oven. Height of the hood should be adjusted until 



the wax is vielted for about one-half its depth. 



clearing agents. Translating this theory 

 into practice it must be obvious that the 

 object to be dehydrated should be sus- 

 pended toward the top of a tall cylinder of 

 dehydrant in order that the water ex- 

 tracted from it may fall toward the bot- 

 tom of the vessel, and that an object for 

 clearing should be held at the bottom of 

 the vessel for the reverse reason. It is, 

 indeed, practically impossible to dehy- 

 drate a large object unless it is so sus- 

 pended. The process of impregnating the 

 tissues with wax lias not, however, provi- 

 ousl}' been discussed and will be tlealt with 

 fully. 



trie bulbs held, at a distance which may be 

 varied, above a series of glass \'ials. Before 

 commencing to embed one fills as many 

 vials as one will require with wax, places 

 them under the reflector, and turns on the 

 current. After a little while it will be oI> 

 served that the absorbed heat has melted 

 the wax. The wax may be melted only at a 

 small surface layer; it may be melted 

 throughout the entire vial; or it may, as is 

 required, be melted in the upper % of the 

 vial. If this last is not achieved the height 

 of the lamp must be varied until, after an 

 hour or two, each of the vials contains 

 about yi of unmolten, opaque wax at the 



