Editors (continued) Transport for Dec. 1892 and Jan. 1893. fol. Zoophilist for Dec. 1892 and Jan. 1893. 4to. Electrical Engineers, Institution of-Journal, No. 101. 8vo. 1893. Index, Vols. XI.-XX. 8vo. 1892. Florence, Biblioteca Nazionale Centrale-Bolletino, Nos. 167-169. 8vo. 1892. Franklin Institute-Journal, Nos. 804, 805. 8vo. 1892. Geographical Society, Royal-Supplementary Papers, Vol. III. Part 2. 8vo. 1892. Geographical Journal, Vol. I. Nos. 1, 2. 8vo. 1893. Geological Institute, Imperial, Vienna-Verhandlungen, 1892, Nos. 11-14. 8vo. Glasgow Philosophical Society-Proceedings, Vol. XXIII. 8vo. 1892. Harvard University-University Bulletin, Nos. 53, 54. 8vo. 1892-3. Johns Hopkins University-American Chemical Journal, Vol. XIV. No. 8. 8vo. 1892. Studies in Historical and Political Science, Tenth Series, No. 12; Eleventh Series, No. 1. 8vo. 1892-3. University Circular, No. 102. 4to. 1893. Linnean Society-Journal, No. 203. 8vo. 1893. Manchester Geological Society-Transactions, Vol. XXII. Part 2. 8vo. 1892. Manchester Literary and Philosophical Society-Memoirs and Proceedings, Vol. I. 8vo. 1892. Massachusetts Institute of Technology, Boston, U.S.A.-Technological Quarterly, Mechanical Engineers, Institution of-Proceedings, 1892, No, 3. 8vo. Meteorological Society, Royal-Meteorological Record, Nos. 45, 46. 8vo. 1892. 1892. Ministry of Public Works, Rome-Giornale del Genio Civile, 1892, Fasc. 9-11. Newton, A. V. Esq. (the Author)-Patent Law and Practice. 8vo. 1893. Payne, Wm. W. Esq. and Hale, Geo. E. Esq. (the Editors)-Astronomy and Astro- Pharmaceutical Society of Great Britain—Journal for Dec. 1892 and Jan. 1893. 8vo. Calendar, 1893. 8vo. Raffard, N. J. Esq. (the Author)-La Locomotive Electrique à Grande Vitesse. 8vo. 1892. Richardson, B. W. M.D. F.R.S. M.R.I. (the Author)—The Asclepiad, Vol. IX. Royal Irish Academy-Proceedings, Series III. Vol. II. No. 3. 8vo. 1892. Russell, The Hon. R., F.R. Met. Soc. M.R.I. (the Author)-Observations on Dew and Saxon Society of Sciences, Royal-Philologisch-Historische Classe: Berichte, 1892, Nos. 1, 2. 8vo. Scottish Society of Arts, Royal-Transactions, Vol. XIII. Part 2. 8vo. 1892. Selborne Society-Nature Notes, Vol. III. Nos. 37, 38. 8vo. 1893. Sociedad Cientifica " Antonio Alzute," Mexico-Memorias, Tomo VI. Numéros 1-4. 8vo. 1892. Société Scientifique de Chili-Actes, Tome II. Livraison 1er. 4to. 1892. 8vo. 1892. Surgeon-General's Office, U.S. Army—Index Catalogue of the Library, Vol. XIII. 4to. 1892. Tacchini, Professor P. Hon. Mem. R.I. (the Author)-Memorie della Societa degli Spettroscopisti Italiani, Vol. XXI. Disp. 11a, 12. 4to. 1892. United Service Institution, Royal-Journal, Nos. 178, 179. 8vo. 1893. United States Department of Agriculture-Monthly Weather Review for September, 1892. 4to. 1892. Publications, 1887-92. 8vo. Weather Bureau, Bulletin, Nos. 5, 6. 8vo. 1892. United States Navy-General Information Series, No. XI. 8vo. 1892. Vereins zur Beförderung des Gewerbfleises in Preussen-Verhandlungen, 1892. Heft 10. 4to. 1892. Victoria Institute-Transactions, No. 102. 8vo. 1892. WEEKLY EVENING MEETING, Friday, February 10, 1893. Sir JAMES CRICHTON-BROWNE, M.D. LL.D. F.R.S. Treasurer and Vice-President, in the Chair. PROFESSOR CHARLES STEWART, M.R.C.S. Pres. L.S. Some Associated Organisms. [No Abstract.] WEEKLY EVENING MEETING, Friday, February 17, 1893. WILLIAM HUGGINS, Esq. D.C.L. LL.D. F.R.S. Vice-President, in the Chair. PROFESSOR A. H. CHURCH, M.A. F.R.S. M.R.I. Turacin, a remarkable Animal Pigment containing Copper. THE study of natural colouring matters is at once peculiarly fascinating and peculiarly difficult. The nature of the colouring matters in animals and plants, and even in some minerals (ruby, sapphire, emerald and amethyst, for example) is still, in the majority of cases, not completely fathomed. Animal pigments are generally less easily extracted and are more complex than those of plants. They appear invariably to contain nitrogen-an observation in accord with the comparative richness in that element of animal cells and their contents. Then, too, much of the coloration of animals, being due to microscopic structure, and therefore having a mechanical and not a pigmentary origin, differs essentially from the coloration of plants. Those animal colours which are primarily due to structure do, however, involve the presence of a dark pigment-brown or black-which acts at once as a foil and as an absorbent of those incident rays which are not reflected. Many spectroscopic examinations of animal pigments have been made. Except in the case of blood- and bile-pigments, very few have been submitted to exhaustive chemical study. Spectral analysis, when uncontrolled by chemical, and when the influence of the solvent employed is not taken into account, is very likely to mislead the investigator. And, unfortunately, the non-crystalline character of many animal pigments, and the difficulty of purifying them by means of the formation of salts and of separations by the use of appropriate solvents, oppose serious obstacles to elucidation. Of blood-red or hæmoglobin it cannot be said that we know the centesimal composition, much less the molecular weight. Even of hæmatin the empirical formula has not yet been firmly established. The group of black and brown pigments to which the various melanins belong still awaits adequate investigation. We know they contain nitrogen (8 to 13 per cent.), and sometimes iron, but the analytical results do not warrant the suggestion of empirical formulæ for them. The more nearly they appear to approach purity the freer the majority of them seem from any fixed constituent such as iron or other metal. It is to be regretted that Dr. Krukenberg, to whom we are indebted for much valuable work on several pigments extracted from feathers, has not submitted the interesting substances he has described to quantitative chemical analysis. I must not, however, dwell further upon these preliminary matters. I have introduced them mainly in order to indicate how little precise information has yet been gathered as to the constitution of the greater number of animal pigments, and how difficult is their study. And now let me draw your attention to a pigment which I had the good fortune to discover, and to the investigation of which I have devoted I am afraid to say how many years. It was so long ago as the year 1866 that the solubility in water of the red colouring matter in the wing-feathers of a plantain-eater was pointed out to me. [One of these feathers, freed from grease, was shown to yield its pigment to pure water.] I soon found that alkaline liquids were more effective solvents than pure water, and that the pigment could be precipitated from its solution by the addition of an acid. [The pigment was extracted from a feather by very dilute ammonia, and then precipitated by adding excess of hydrochloric acid.] The next step was to filter off the separated colouring matter, and to wash and dry it. The processes of washing and drying are tedious and cannot be shown in a lecture. But the product obtained was a solid of a dark crimson hue, non-crystalline, and having a purple semi-metallic lustre. I named it turacin (in a paper published in a now long-defunct periodical The Student and Intellectual Observer,' of April, 1868). The name was taken from " Touraco," the appellation by which the plantain-eaters are known-the most extensive genus of this family of birds being Turacus. From the striking resemblance between the colour of arterial blood and that of the red touraco feathers, I was led to compare their spectra. Two similar absorption bands were present in both cases, but their positions and intensities differed somewhat. Naturally I sought for iron in my new pigment. I burnt a portion, dissolved the ash in hydrochloric acid, and then added sodium acetate and potassium ferrocyanide. To my astonishment I got a precipitate, not of Prussian blue, but of Prussian brown. This indication of the presence of copper in turacin was confirmed by many tests, the metal itself being also obtained by electrolysis. It was obvious that the proportion of copper present in the pigment was very considerable— greatly in excess of that of the iron (less than 5 per cent.) in the pigment of blood. Thus far two striking peculiarities of the pigment had been revealed, namely, its easy removal from the web of the feather, and the presence in it of a notable quantity of copper. Both facts remain unique in the history of animal pigments. The solubility was readily admitted on all hands, not so the presence of copper. It was suggested that it was derived from the Bunsen burner used in the incineration, or from some preservative solution applied to the bird-skins. And it was asked "How did the copper get into the feathers?" The doubters might have satisfied themselves as to copper being normally and invariably present by applying a few easy tests and by the expenditure of half-a-crown in acquiring a touraco wing. My results were, however, confirmed (in 1872) by several independent observers, including Mr. W. Crookes, Dr. Gladstone, and Mr. Greville Williams. And in 1873 Mr. Henry Bassett, at the request of the late Mr. J. J. Monteiro, pushed the inquiry somewhat further. I quote from Monteiro's Angola and the River Congo,' published in 1875 (vol. ii. pp. 75-77). "I purchased a large bunch of the red wing-feathers in the market at Sierra Leone, with which Mr. H. Bassett has verified Professor Church's results conclusively," &c., &c. Mr. Bassett's results were published in the Chemical News in 1873, three years after the appearance of my research in the Phil. Trans. As concentrated hydrochloric acid removes no copper from turacin, even on boiling, the metal present could not have been a mere casual impurity; as the proportion is constant in the turacin obtained from different species of touraco, the existence of a single definite compound is indicated. The presence of traces of copper in a very large number of plants as well as of animals has been incontestably established. And, as I pointed out in 1868, copper can be readily detected in the ash of banana fruits, the favourite food of several species of the "turacin-bearers." The feathers of a single bird contain on the average two grains of turacin, corresponding to 14 of a grain of metallic copper; or, putting the amount of pigment present at its highest, just one-fifth of a grain. This is not a large amount to be furnished by its food to one of these birds once annually during the season of renewal of its feathers. I am bound, however, to say that in the blood and tissues of one of these birds, which I analysed immediately after death, I could not detect more than faint traces of copper. The particular specimen examined was in full plumage; I conclude that the copper in its food, not being then wanted, was not assimilated. Let us now look a little more closely at these curious birds themselves. Their nearest allies are the cuckoos, with which they were formerly united by systematists. It has, however, been long conceded that they constitute a family of equal rank with the Cuculidæ. According to the classification adopted in the Natural History Museum, the order Picariæ contains eight sub-orders, the last of which, the Coccyges, consists of two families, the Cuculida and the Musophagidæ. To the same order belong the Hoopoes, the Trogons, the Wood-peckers. The plantain-eaters or Musophagidæ are arranged in six genera and comprise 25 species. In three genera-— Turacus, Gallirex, and Musophaga-comprising eighteen species, and following one another in zoological sequence, turacin occurs; from three genera (seven species)-Corythæola, Schizorhis, and Gymnoschizorhis-the pigment is absent. [The coloured illustrations to H. Schlegel's Monograph (Amsterdam, 1860) on the Musophagida were exhibited]. The family is confined to Africa: 8 of the turacinbearers are found in the west sub-region, 1 in the south-west, 2 in |