_Concentrated Hydrochloric Acid._—When exposed to the concentrated aqueous acid at ordinary temperatures, ligno-cellulose undergoes a profound structural modification, and is largely converted into soluble bodies. The disintegrated residue reacts with chlorine similarly to the original jute, but the quantity of cellulose isolated by subsequent treatment with alkaline solutions is only 50 per cent. of the original. Since jute cellulose, after isolation, exhibits under similar treatment a much smaller conversion into soluble products, 10 per cent. as compared with 33, we have here further evidence that the cellulose is present in the fibre in a condition chemically different from that of the isolated cellulose. _Sulphuric Acid._—On triturating the fibre with the concentrated acid, it dissolves to a brownish-purple solution; on pouring this solution into water, a substance is precipitated in dark-brown flocks; when dried it has the following composition: C 64·4 H 4·4 O 31·2 The solution yields on distillation furfural and acetic acid. _Nitric and Sulphuric Acids._—(1 : 2 by vol.)—By the action of these acids ligno-cellulose is converted into yellow-coloured explosive compounds, preserving all the external features of the original fibre, and showing a close resemblance to the pyroxylins. The increase in weight resulting from the fixation of the {23} nitric acid residue is approximately equal to that of cotton “nitrated” under the same conditions. They are freely soluble in acetone. On examination they prove to be homogeneous. If the fibre be warmed with the mixture after the first reaction is completed, it dissolves. The solution is found to contain oxalic, succinic, and suberic acids, but no aromatic nitro-derivatives, whereas if ligno-cellulose contain a benzene nucleus, as has been supposed, such derivatives could not fail to be formed under these conditions. _Animal Digestion of Ligno-cellulose._—It has long been known that the urine of herbivorous animals contains hippuric acid, or benzoyl glycocine, as a normal constituent, and it has been shown that the benzoyl radicle necessary to form this body by reacting with the glycocine of the liver, is a product of the digestion of ligno-cellulose. On the other hand, it has been shown that ligno-cellulose contains no benzene compounds as such. We have therefore, in this fact additional evidence that a portion of the complex ligno-cellulose molecule is in what we may term a potentially aromatic condition. _Distribution of Ligno-celluloses._—As already indicated, the distribution of the ligno-celluloses is extremely wide; they are met with in every variety of vegetable tissue, and their presence is readily ascertained by the reaction of chlorination already described. Of these ligno-celluloses most closely allied to jute, we may mention the stony concretions of pears (glycodrupose) and the main tissue of fir wood (glycolignose).