74 ■ MATERIALS AND PROCESSES OF SLIDE-MAKING 



line of frost on the side just reaches the top. Cutting should start at once using 

 a rather slow, even stroke. The correct degree of freezing is vital to success 

 but can only be learned by experience. 



Mounting and Staining Frozen Sections. Fairly thick frozen sections may 

 be handled with section lifters and passed through any of the stains described 

 in Chapter 3. Sections of fatty tissue are always handled in this manner and 

 should be stained by the method discussed on page 29. 



If complex staining techniques are to be applied, however, it is better to fix 

 the section or sections to a slide. One of the best techniques involves two solutions: 



Gravis' Adhesive: 

 Water 100 ml. 



Agar 0.1 Gm. 



Camphor 0.1 Gm. 



Dissolve the agar in boiling water. Filter and add the camphor to the 

 hot filtrate. 



Zimmerman's Lacquer: 

 Absolute alcohol 50 ml. 

 Anhydrous ether 50 ml. 

 Pyroxylin U.S. P. 

 or Parlodion 0.5 Gm. 



Gum mastic 0.1 Gm. 



The first solution is used exactly as water is used (see p. 68) to flatten a 

 paraffin section. The amount of warming necessary depends on the degree of 

 wrinkling of the section but is usually less than for paraffin ribbons. As soon 

 as the slide has been drained, absolute alcohol is dropped gently on the section 

 from a pipette, left for a few moments, and then drained off. A few moments 

 now suffice to dry the sections, which become opaque. A piece of lens paper 

 is then laid over the slide, and each section is pressed firmly with the finger. 

 The slide is now quickly dipped in absolute alcohol, drained, and dipped in 

 Zimmerman's solution. This last is allowed to evaporate from the surface, 

 leaving behind a coat which will hold the section in place through subsequent 

 staining techniques. Any of the stains discussed in Chapter 3 may be used 

 save those involving differentiation in absolute alcohol which would dissolve 

 the lacquer. The slides are treated exactly as though they carried paraffin sec- 

 tions except that the final transfer should be from 95 per cent alcohol to ter- 

 pineol to xylene. Even terpineol has a slight solvent action on the slide which 

 should remain in it, therefore, only long enough to remove the alcohol. 



