Woody fibre is as abundant a constituent of the straw of the cereals as starch is of their seeds, and if the two substances were equally digestible, straw would be a very valuable food--superior even to the potato. At one time it was the general belief that woody fibre was incapable of contributing in the slightest degree to the nutrition of animals, but the results of recent investigations prove that it is, to a certain extent, digestible. In the summer of 1859 two German chemists, Stöckhardt and Sussdorf, made a series of experiments, with the view of ascertaining whether or not the cellulose[30] of the food of the sheep is assimilated by that animal. The results of this inquiry are of importance, seeing that they clearly prove that even the hardest kind of cellulose--_sclerogen_, in fact--is capable of being assimilated by the Ruminants. The animals selected were two wethers, aged respectively five and six years. They were fed--firstly, upon hay alone; secondly, upon hay and rye-straw; thirdly upon hay and the sawdust of poplar wood, which had been exhausted with lye (to induce the sheep to eat the sawdust, it was found necessary to mix through it some rye-bran and a little salt); fourthly, hay and pine-wood sawdust, to which was added bran and salt; fifthly, spruce sawdust, bran and salt; sixthly, hay, pulp of linen rags (from the paper-maker), and bran. The experiments were carried on from July till November, excepting a short time, during which the animals were turned out on pasture-land, to recover from the injurious effects of the fifth series of experiments--produced probably by the resin of the spruce. The animals, together with their food, drink, and egesta, were weighed daily. The amount of cellulose in the food was determined, and the proportion of that substance in the egesta was also ascertained; and as there was a considerable discrepancy between the two amounts, it was evident that the difference represented the weight of the cellulose assimilated by the animals. In this way it was ascertained that from 60 to 70 per cent. of the cellulose of hay, 40 to 60 per cent. of the cellulose of straw, 45 to 50 per cent. of the cellulose of the poplar wood, 30 to 40 per cent. of the cellulose of the pine, and 80 per cent. of the cellulose of the paper pulp was digested. In stating the results of his analyses of the straws, Professor Voelcker sets down as "digestible" that portion of the cellulose which he found to be soluble in dilute acids and alkaline solutions; but he admits that the solvents in the stomach might dissolve a larger amount. The results of the experiments of Stöckhardt and Sussdorf prove that 80 per cent. of the cellulose of paper (the altered fibre of flax) is assimilable, and it is, therefore, not unreasonable to infer that the cellulose of a more palatable substance than paper might be altogether digestible.