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Show 364 MR. SORBY ON THE COLOURING OF BIRDS' EGGS. [May 4, out the kind of arguments made use of in my late paper in the ' Monthly Microscopical Journal,' the conclusions to which we are led by the above-described facts are that oorhodeine is in some way or other closely related to cruentine, but not identical with it, as shown not only by the well-marked difference in the spectra, but also by the difference in their solubility and power of resisting the decomposing action of powerful reagents. In the present state of our knowledge the most plausible explanation of all the facts is that perhaps oorhodeine and cruentine contain some common coloured radical of the same chemical or physical constitution, combined with some other substance which is itself colourless, and that this second constituent is not the same in oorhodeine as in cruentine, but differs sufficiently to modify the general properties and to slightly alter the size of the ultimate molecules and so as to cause them to be related to waves of light of a little different length. It must, however, be borne in mind that I advance these views merely as being the most probable explanation of the facts. Assuming them to be true, they lead to the conclusion that the oorhodeine of birds' eggs is derived from the red colouring-matter of the blood, not by any mere mechanical exudation, but by some unknown physiological process of secretion, which breaks up the highly complex molecule of haemoglobin into one which can be formed artificially by heating it with strong sulphuric acid; but in the living organism it combines with a second substance differing from that with which it combines when the change is effected by the action of hot strong sulphuric acid. Whether this view of the subject be in all respects true or not, it at all events appears to me very plausible and well worthy of further examination, as pointing to the source of one of the most important colouring-matters of birds' eggs. RELATIONS OF THE OOCYANS. In their normal condition the faeces of man, and probably those of many other animals, contain a yellow colouring-matter, which by oxidization yields a substance closely related, if not identical, with a product of the oxidization of the bilirubin of bile described by Jaffe* and by Heynsius and Campbell f. When extracted from faeces by alcohol without contact with the air, it gives a spectrum which cuts off the blue end without any definite band; but when exposed to the air or treated with some oxidizing reagent, the solution becomes orange-coloured, and the spectrum shows a well-marked, dark, moderately broad absorption-band between the blue and the green, having its centre at wave-length 495 millionths of a millimetre. The addition of an excess of ammonia immediately removes this band without producing any well-marked change in the colour. Now I find, on comparing this substance with the product of the oxidization of the two species of oocyan, which gives the spectrum shown by fig. 2, that there is a close agreement in general characters, but yet a well-marked difference. The band * Virchow's Archiv, vol. xlvii. p. 262. t Pfliiger's Archiv, vol. iv. p. 520. |