910 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



shellac, by which an excellent fixative is obtained that never shows 

 any traces of granulation. The fixative is applied by a fine brush to 

 the cold slide. 



Mayer prepares the solution in the following manner : — 



1. Dissolve one part of bleached shellac in five parts of absolute 

 alcohol. 



2. Filter the solution and evaporate the alcohol on a water-bath. 

 A yellowish residue quite stiff when cold is thus obtained. If any 

 cloudiness arises during evaporation, the solution must be filtered 

 again. 



3. Dissolve the shellac residue in pure carbolic acid on a water- 

 bath. A concentrated solution of carbolic acid is obtained by ex- 

 posing the crystals to the air until they dissolve, or by adding a small 

 amount of water (about 5 per cent.). 



The quantity of acid should be sufficient to give a thickish liquid 

 when cold. 



This fixative is painted on to the cold slide with a brush, at the 

 time of using. The sections are then put in place, and the slide left 

 in the oven of a water-bath for some minutes (10-15 minutes is found 

 sufficient). The carbolic acid is thus evaporated, leaving a perfectly 

 transparent stratum of shellac on the slide. The sections are next 

 freed from paraffin in the ordinary way and mounted in balsam. 



This method is considered to be the best and simplest for fixing 

 stained sections. 



The shellac can be dissolved directly in carbolic acid, but then 

 the fluid must stand a long time in order to become clear, as it can- 

 not be filtered. For this reason it is preferable to dissolve first in 

 alcohol. 



[According to a note just received, Mayer now prepares the shellac 

 as follows : — 



The shellac is pulverized and heated with crystals of colourless 



carbolic acid until it dissolves. In 

 filtering, the funnel should be 

 heated over a flame. It will filter 

 slowly but quite well. If it is too 

 thick, crystals of carbolic acid may 

 be added until the desired consis- 

 tency is reached.] 



Slide - Boxes. — Messrs. Beck 

 have supplied us with one of the 

 most convenient slide-boxes that we 

 have yet met with, and very econo- 

 mical in price (8s. 9cZ.). It consists 

 of a cloth-covered pasteboard box 

 15 in. X 8^ in. X 3^ in. which con- 

 tains twelve trays of the form 

 shown in fig. 219, holding twenty- 

 four slides each (or 288 in all). 

 The bottom of the tray is divided into four parts by two cross-pieces, 

 and the slides are prevented from shifting by shutting down the two 



Fig. 219. 



