and burns away, leaving no ash. When heated in a test-tube or between watch-glasses, it gives a small quantity of amorphous brown sublimate with a few crystalline needles. It dissolves in boiling alco- hol, giving a bright yellowish-red solution, which, on cooling, deposits crystalline needles, becoming almost colourless. It is moderately soluble in ether, benzol, and glacial acetic acid ; very soluble in chloroform. The chloroformic solution shows no absorption bands, only obscuration in the blue. It is quite insoluble in caustic potash liquor even on boiling. It dissolves in concentrated sulphuric acid, giving a dull red solution, which, after the addition of a considerable quantity of acid, shows no absorption bands, only obscuration in the blue and green ; on the addition of water, the solution turns reddish-yellow without giving any precipitate, but on standing for a short time the colour turns to a fine violet, and then shows a broad ill-defined absorption liand between the red and green. Not showing any very character- istic reaction but the one last mentioned, it must remain doubtful how and where it originates. It may possibly be a constituent of the green parts of plants not hitherto observed, though I believe it myself to be a derivative of chlorophyll meaning by chlorophyll the ensemble of the colouring matters of green leaves formed by some unknown process in the animal economy, but the fact of its solutions showing no absorption bands does not lend countenance to this view. Having also observed it on one occasion only, I do not feel justified in giving it a name or in placing it in any known category of vegetable or animal colouring matters.
Another constituent of the faeces remains to be mentioned. It was referred to above as showing in solution the absorption spectrum of phylloxanthin. After all the substances capable of assuming a crys- talline form have been separated from the alcoholic extract of the faeces, this phylloxanthin-like substance is found in the final mother liquor. I have not succeeded in obtaining it in a crystalline or any other definite form, on account probably of the large quantity of fatty matter with which it is associated ; but there is no reason, I think, to suppose that it differs essentially from the phylloxanthin described in previous communications as a product of the action of acids on chloro- phyll.
The conclusions to which the experiments above described lead may be summarised as follows :
1. The faeces of animals supplied with green vegetable food only such at least as have so far been examined contain no chlorophyll, but in its place substances which must be supposed to be derivatives of chlorophyll, formed partly by the action of acids on the chlorophyll of the food, partly by some agency to which the latter is subjected in its passage through the body.
2. Of these substances, one seems to be identical with phylloxanthin.
