122 FROZEN SECTIONS 



they dry, the gelatin surface being inside so as to avoid dust. 

 These shdes will dry quickly in a warm place. The gelatin 

 solution does not keep well and it is better to make a supply of 

 slides just for the work in hand. When handling the slides the 

 gelatin side can be discovered by breathing on the slide, the 

 moisture showing on the side without the gelatin. If the 

 gelatin is staining visibly in the finished preparations, you are 

 smearing the slides too thickly when preparing. 



228. Miller's Method for Mounting Frozen Sections. E. G. 

 Miller (J. R. Micr. Soc, 1930), who is an expert in the frozen 

 section technique, mounts as follows : a glass rod is drawn out 

 and bent at an angle of 130 degrees, cut not less than an inch 

 from the bend, and the cut end rounded off in the flame. A Petri 

 dish is filled with distilled water and the best section from the 

 other dish containing the sections is selected, and the short limb 

 of the glass rod passed under the section to pick it up. A gelatined 

 slide is now taken in the left hand, plunged into the Petri dish of 

 distilled water, holding it just below and parallel to the surface. 

 Holding the glass rod in the right hand, dip into the water and 

 allow the section to float clear, gently raising the slide out of the 

 water, catching the section in the middle of the slide. Tilt the 

 slide gently, allowing the water to run off. Place the slide on the 

 bench, put a cigarette paper previously wetted on both sides 

 over the section, and press down with a pad formed by a folded 

 filter paper, rubbing one way so as to press without shifting 

 either paper. Remove the pad of filter paper and gently peel 

 off the cigarette paper. If the section is fatty or sticky, it may 

 adhere to the cigarette paper. To remedy, wet paper with a 

 few drops of pyridine in 50 per cent, alcohol. If not already 

 fixed, place the section in a corked specimen tube or staining jar, 

 at the bottom of which is a plug of cotton wool soaked in strong 

 formalin. This jar should be placed on a warm plate, or be 

 warmed so that the formaldehyde gas comes off well. Leave 

 slide fifteen to thirty seconds to fix. Transfer to 10 per cent, 

 formol saline. 



229. Staining Frozen Sections. Sections or smears which have 

 just been fixed are difficult to stain. This can be remedied by 

 immersing overnight in 90 per cent, alcohol, after which they will 

 stain evenly. But this may not be desirable and it may be 

 necessary to proceed straight away. The most beautiful method 

 is undoubtedly Hollande's chloro-carmine-iron alum. Some of 

 Mr. E. G. Miller's slides are very fine, showing both chromosomes 

 and mitochondria well. For sections which do not stain well, 

 he recommends leaving overnight in formol-saline. If they do not 

 stain properly, treatment with H2O2 should then be tried. 

 Slides should be left in one volume of HgOa to nine volumes of 

 70 to 90 per cent, alcohol for approximately thirty minutes. 



