For such as wish to prepare this substance, I may state, as the result of my experience, that it can only be obtained from the faeces of cows or other herbivora that have been fed exclusively on grass or other green vegetable food ; those of stall-fed cattle, nourished as they usually are to a great extent with oil cake, yield none, on account perhaps of the large amount of fatty matter presentfin that case in the faeces. I may add that the solid excrements of sheep that have been at pasture for some time and living on herbage only, on being treated as above described, yield the same substance, but I have made no experiments with the faeces of other herbivora. I imagine that the yield of this peculiar substance is greatest from material collected in spring or early summer ; but this, if correct, may be due to other causes than difference of season.
This substance not having, so far as I can ascertain, been previously observed, I propose to call Scatocyanin, a name kindly suggested to me by Professor Wilkins, of Owens College. Its chief properties are as follows : Under the microscope it appears in the form of thin rhombic plates or elongated flat prismatic crystals, which are pale brown by transmitted light, of a purplish-blue colour with a brilliant metallic lustre by reflected light. When heated between watch- glasses it is decomposed without melting or swelling much or yielding any sublimate ; heated further on platinum, it burns away, leaving a little ash. It is almost insoluble in boiling alcohol, ether, carbon disulphide, and benzol, but it dissolves, though not readily, in chloro- form, giving a solution which shows an absorption spectrum of five bands, almost identical with those of phyllocyanin. It dissolves in boiling glacial acetic acid, giving a fine crimson solution, which, when sufficiently dilute, shows an absorption spectrum of four bands of which the two first are well defined, the third faint with some obscura- tion between it and the second band, the fourth band also faint and not well defined (see fig.). From a saturated solution in boiling acetic acid the substance separates on cooling and standing in lustrous pur- plish-blue needles.
It dissolves in concentrated sulphuric acid with a brilliant grass- green colour, which, on standing, changes to purplish-blue. The solution now shows a characteristic absorption spectrum of five bands, of which the first and fifth are faint and poorly defined, the second and third well defined, but the fourth only moderately so, while there is much obscuration between the fourth and fifth bands, with just a trace of a sixth band in the green between the fifth band and the total obscuration (see fig.).
The sulphuric-acid solution on being mixed with several times its volume of water changes its colour from purplish-blue to a fine purple without giving any precipitate and without showing any change in its absorption spectrum. On standing, however, for some time the liquid
