THE CELLULOSE METHOD 
131 
solution of cellulose acetate necessary for softening the tissues varied with 
the hardness of the wood, the minimum time for soft woods being two days; 
for woods such as oak and beech, at least six days are required. Experi¬ 
ments were tried with sal (Shorea robusta ) and Pyingadu (Xylia dolabriformis ), 
one of the Indian ironwoods, which is extremely hard. After fourteen days 
in the cellulose acetate solution it was possible to obtain transverse sections 
of these hard woods. The cellulose acetate solution is therefore capable of 
softening even the hardest wood in a relatively short time. 
In order to stain sections—either hand or microtome—obtained by this 
method, it is necessary to wash them in pure acetone for 1 to 2 minutes to 
remove the cellulose acetate, wash in alcohol 1 to 2 minutes, and pass on to 
the stains selected. Various staining methods for cell walls—such as anilin 
chloride, methylene blue, and Congo red, ammoniacal fuchsin and Kleinen- 
berg’s haematoxylin, etc.—were tried with success. A comparison with 
stained sections of untreated wood revealed no differences. Delicate tissues 
in the wood and hyphae of fungi infecting the wood also stain well and are 
unaffected by the treatment. 
A satisfactory method of preparing sections of hard vegetable structures 
is therefore supplied by the use of a 12 per cent solution of cellulose acetate 
in pure acetone for softening and embedding.—H. S. Williamson, Imperial 
College of Science and Technology. 
Correspondence with Mrs. Williamson indicates that the various 
brands of cellulose acetate behave differently. Cellulose acetate 
obtained from wood is unsatisfactory. We found that cellulose ace¬ 
tate made from photographic films was also unsatisfactory. Mrs. 
Williamson used a cellulose acetate sold by Cellon (Richmond) Ltd., 
22 Cork Street, London, England, and manufactured by the Societe 
Chemique des Usines du Rhone. The time may be shortened by 
keeping the temperature at 40° C. 
In making the solution, use 12 g. of cellulose acetate to 100 c.c. 
of pure acetone. 
It would be worth while to try to adapt this method to the paraffin 
method. 
