PRACTICAL PROCESSES IN VEGETABLE HISTOLOGY. 71 
As the solution of cellulose can only be effected by a large 
quantity of nitrite of ammonia care must be taken to keep a con- 
stant current of the liquid passing between the two glasses between 
which the preparation is compressed. For this purpose pieces of 
filtering paper are used, which absorb the liquid at the edge of the 
cover-glass, whilst some drops of the solvent are placed at the 
opposite edge. ‘The operation is hastened by disusing the cover- 
glass where large sections are being treated. 
When the preparations are numerous and resisting they can be 
shaken together in a little flask filled with Schweitzer’s liquid, and 
subjected to several washings. This is the most rapid process. 
But if the preparations are at all delicate the first method alone is 
practicable ; the operator should follow under the Microscope the 
different stages of the solution. The observation is easy with a 
low power ; “put directly it requires more than 200 diameters it 
becomes troublesome. In this case it is better to increase the 
power of the eye-piece alone ; high power objectives are inappro- 
priate, the distance of their front lens from the preparation is so 
small that they risk being wetted by the reagent. 
The butyric fermentation offers a slower but more accurate 
means of isolating in a preparation all the non-cellulose membrane 
by determining the cellulose. The organs or the sections from 
which we wish to eliminate the purely cellulose portions are placed 
in a glass of water, to which are added pieces of radish-roots, 
haricot beans, or broad beans, a very smad/ quantity of sugar and 
powdered carbonate of lime. The mixture is shaken up, and left 
exposed to the air. The fermentation is increased by keeping the 
vessel in a temperature of about 30° C. 
When, carbonate of lime being in excess, there is no further dis- 
engagement of gas, the Lacillus amylobacter has formed its spore, 
and the fermentation has ceased; all the cellulose has then been, 
by a series of successive hydrations, converted into glucose, and 
the glucose decomposed into carbonic acid and butyric acid. The 
role of the carbonate of lime is to allow the formation of butyrate 
of lime as butyric acid is produced ; this acid, free and accumu- 
lating in the liquid, would arrest the development of the Bacillus 
long before the destruction of all the cellulose. 
Like Schweitzer’s solution, the butyric ferment does not attack 
cellulose whose condensation exceeds (C,H,.O;),. The action of 
the microbe is indeed so special that it is only exercised on a 
certain kind of this compound, although no chemical reagent shows 
two varieties of it. Thus cells of Chara and £lodea, although 
dissolving in nitrite of ammonia, are not altered by Bacillus 
amylobacter. 
_ Generally this microscopical agent does not affect starch, which 
is,a lower polymer than cellulose. Nevertheless, Van Tieghem 
