Making Sections 



153 



Fig. 116. Flooding the ribbons. 



time for the heat to pass from the glass to the fluid, rewarmed, and so on 

 until the sections are observed to be flat. The utmost care must be taken 

 at this point, for, if the paraffin is permitted to melt, it will be difficult 

 later, if not impossible, to cause the sections to remain attached to the 

 glass. As soon as the sections are flattened, the slide is gently tilted back- 

 ward toward the hand to run off the excess water against the thumb, leav- 

 ing the sections stranded in place. The slide is usually placed on a thermo- 

 statically controlled hot plate (seen in Fig. 125) and permitted to dry. 

 Most people leave their slides overnight, but frequently an hour would be 

 sufficient. Dryness can be gauged without the least trouble by the fact 

 that a moistened slide shows the wax to be more or less opalescent, while 

 on a properly dried slide it is almost glass-clear. 



The method just described is susceptible of several variations, which 

 may be noted briefly. Some people neither drain the water from the slide 

 nor heat the slide over the lamp but merely place it, as soon as the water 

 has been added to it, on the thermostatically controlled hot plate. This 

 permits the sections to dry and to flatten at the same time. The objection 

 to this procedure is that air contained in the water used for flattening al- 

 most invariably comes out in the form of bubbles, which accumulate 



