384 PREPARATIONS BY THE PARAFFIN METHOD [Ch. XI 



half an hour or more. The slower drying in air is better if one has 

 plenty of time. 



Some tissues are very difficult to get perfectly smooth, as just de- 

 scribed. If fine wrinkles persist, one can sometimes overcome the 

 difficulty by letting the slide cool and then covering with a piece of 

 fine tissue paper slightly moistened; press down firmly with the ball 



Fig. 230. Lantern with Daylight Glass. The Top is Flat and Serves 



Well for Spreading Sections. 



(From the Anatomical Record). 



of the finger on the sections. Then take hold of the edge of the 

 paper and roll it off the sections. Unless one is careful the sections 

 are liable to come away with the paper instead of adhering to the 

 slide. 



As the water dries out the spread sections come in very close con- 

 tact with the glass and adhere quite firmly to it. The thinner the 

 sections the more tightly do they stick. This makes it possible to 

 perform the rest of the operations on the slide. One has to be care- 

 ful not to let strong currents strike the sections. 



§ 621. Deparaffining in xylene. — This is accomplished by using a 

 solvent of paraffin. The best and safest one to use in a laboratory 



