[Footnote 4: The action of alkaline substances dissolved from the glass must be taken into account in this decomposition.] _Decomposition by means of ferments, &c._—The soluble ferment of the foxglove has been found to convert cellulose into glucose and dextrin. The fluid from the vermiform appendix of the rabbit has also been found to digest cellulose with liberation of marsh gas and formation of a soluble compound which reduces cupric oxide in alkaline solution. _Humus._—In the natural decay of cellulosic structures a large quantity of marsh gas is formed, and solid products are formed, which are usually known as humic or ulmic substances. These bodies are amorphous, are largely dissolved by alkaline solutions, and are attacked by chlorine gas in presence of moisture, yielding yellow coloured chlorinated derivatives whose composition has a general resemblance to the chlorinated compounds obtained from the compound celluloses, to be hereafter described. The most important part which ulmic substances play in the economy of nature, is in the composition of soils. It is doubtful whether they act directly as fertilisers, but by their action upon the mineral constituents of soils they contribute to the supply of these necessary elements of growth to the plant. _Synthesis of Cellulose._—A transformation of certain soluble carbo-hydrates into cellulose, which may be regarded as a proximate synthesis of cellulose, has recently been brought to light. This is set up spontaneously in beet-juice, and results in the formation of a hard white substance, insoluble in boiling dilute potash, soluble in the ammonio-copper reagent, converted by sulphuric acid into dextrin and sugar, and by nitric acid into oxalic acid. On adding some of these cellulose lumps to a solution of pure cane-sugar, a further transformation of the saccharose into the same substance is brought about. At the same time there is simultaneously produced a gummy substance, which is precipitated by {16} alcohol as a white amorphous caoutchouc-like mass, of the same composition as cellulose, but swelling up with water, and otherwise differing in its physical properties from cellulose. This latter substance is also formed by the action of diastaste upon a solution of saccharose. The process of cellulosic fermentation may be represented by the equation: n. (C_{12}H_{22}O_{11}) = n. (C_{6}H_{10}O_{5}) + n. (C_{6}H_{12}O_{6}) Saccharose. Cellulose. Glucose.