was not precipitated by iron or mercuric chloride, copper sulphate, nor by neutral lead acetate; but was precipitated by basic lead acetate, basic iron sulphate, and excess of tannin. Its elementary composition is--carbon, 45·91: hydrogen, 6·57; nitrogen, 17·82; oxygen, 29·60; and Reimer proposes the following equation as representing its relation to hide fibre:-- Hide fibre. Water. Coriin. C_{30}H_{46}N_{10}O_{12} + O + 2H_{2}O = C_{30}H_{50}N_{10}O_{15}. [Footnote C: Dingler's Polyt. Journal, vol. 220, p. 167.] _Hide Albumen._--The fresh hide, besides this coriin (which, very possibly, is only evolved by the action of the lime), contains a portion of actual albumen, viz. that of the blood serum and of the lymph, which is not only contained in the abundant blood-vessels, but saturates the fibrous connective tissue, of which it forms the nourishment. This albumen is mostly removed by the liming and working on the beam, which is preparatory to tanning. Probably for sole-leather, the albumen itself would be rather advantageous if left in the hide, as it combines with tannin, and would assist in giving firmness and weight to the leather. It is, however, for reasons which will be seen hereafter, absolutely necessary to get rid of any lime which may be in combination with it. The blood also must be thoroughly cleansed from the hide before tanning, as its colouring matter contains iron, and, in combination with the tannin, would give a bad colour. The reactions of blood and lymph albumen are very similar to those of ordinary white of egg. It is precipitated by strong mineral acids, especially nitric, and also by boiling. The precipitate produced by strong hydrochloric acid redissolves by the aid of heat to a blue or purple solution. Tribasic phosphoric, tartaric, acetic, and most other organic acids, do not precipitate moderately dilute solutions of albumen, but convert it into a sort of jelly, which, like gelatin, does not coagulate, but liquefies on heating. It is precipitated by neutral salts of the alkali metals. Blood-albumen slightly acidified (with acetic acid) is precipitated by potassium ferrocyanide. It is not precipitated by dilute infusions of oak bark, but is rendered uncoagulable by heat, hence it cannot be employed to remove tannins from their solutions. _Elastic Fibres._--The elastic or yellow fibres of the hide are of a very stable character. They are not completely dissolved even by prolonged boiling, and acetic acid and hot solutions of caustic alkalies scarcely attack them. Probably they do not combine with tannin, and are very little changed in the tanning process.