COLUMBIA colouring matters about which we possess definite chemical knowledge, as they have been isolated, purified, and analysed. Most of the bile pigments of mammals have likewise been isolated and studied chemically, and all of these are fully described in the text-books of physiology and physiological chemistry. Haemoglobin, though physiologically of great importance in the respiratory process of vertebrate animals, is yet seldom used for surface pigmentation, except in the face of white races of man or in other parts in monkeys, &c. In some worms the transparent skin allows the haemoglobin of the blood to be seen through the integument, and in certain fishes also the haemoglobin is visible through the integument. It is a curious and noteworthy fact that in some invertebrate animals in which no haemoglobin occurs, we meet with its derivatives. Thus haematin is found in the so-called bile of slugs, snails, the limpet, and the crayfish. In sea-anemones there is a pigment which yields some of the decomposition - products of haemoglobin, and associated with this is a green pigment apparently identical with biliverdin (C16Hj8lSr204), a green bile pigment. Again, haematoporphyrin is found in the integuments of star-fishes and slugs, and occurs in the “ dorsal streak ” of the earth-worm (Lumbricus terrestris), and perhaps in other ' species. Haematoporphyrin and biliverdin also occur in the egg-shells of certain birds, but in this case they are derived from haemoglobin. Haemoglobin is said to be found as low down in the animal kingdom as the Echinoderms, e.g., in Ophiactis virens, and Thyonella gemmata. It also occurs in the blood of Planorbis corneus, and in the pharyngeal muscles of other mollusca. A great number of other pigments have been described; for example, in the muscles and tissues of animals, both vertebrate and invertebrate, are the histohaematins, of which a special muscle pigment, myohaematin, is one. In vertebrates the latter is generally accompanied by haemoglobin, but in invertebrates—with the exception of the pharyngeal muscles of the mollusca—it occurs alone. Although closely related to haemoglobin or its derivative haemochromogen, the histohaematins are yet totally distinct, and they are found in animals where not a trace of .haemoglobin can be detected. Another interesting pigment is turacin, which contains about 7 per cent, of nitrogen, found by Professor Church in the feathers of the Cape lory and other plantain-eaters, from which it can be extracted by water containing a trace of ammonia. It has been isolated, purified, and analysed by Professor Church. From it may be obtained turacoporphyrin, which is identical with haematoporphyrin, and gives the band in the ultra-violet which Soret and subsequently Gamgee have found to be characteristic of haemoglobin and its compounds. Turacin itself gives a peculiar two-banded spectrum, and contains about 7 per cent, of copper in its molecule. Another copper-containing pigment is haemocyanin, which in the oxidized state gives a blue colour to the blood of various mollusca and arthropoda. Like haemoglobin, it acts as an oxygen-carrier in respiration, but it takes no part in surface coloration. A class of pigments widely distributed among plants and animals are the lipochromes. As their name denotes, they are allied to fat and generally accompany it, being soluble in fat solvents. They play an important part in surface coloration, and may be greenish, yellow, or red in colour. They contain no nitrogen. As an example of a lipochrome which has been isolated, crystallized, and purified, we may mention carotin, which has recently been found in green leaves. Chlorophyll, which is so often associated with a lipochrome, has been found in some Infusoria, and in Hydra and Spongilla, &c. In some cases
151
it is probably formed by the animal; in other cases it may be due to symbiotic algae, while in the gastric gland of many Mollusca, Crustacea, and Echinodermata, it is derived from food-chlorophyll. Here it is known as entero-chlorophyll. The black pigments which occur among both vertebrate and invertebrate animals often have only one attribute in common, viz., blackness, for among the discordant results of analysis one thing is certain, viz., that the melanins from vertebrate animals are not identical with those from invertebrate animals. The melanosis or blackening of insect blood, for instance, is due to the oxidation of a chromogen, the pigment produced being known as a uranidine. In some sponges a somewhat similar pigment has been noticed. Other pigments have been described, such as actiniochrome, echinochrome, pentacrinin, antedonin, polyperythrin (which appears to be a haematoporphyrin), the floridines, spongioporphyrin, &c., which need no mention here; all these pigments can only be distinguished by means of the spectroscope. Most of the pigments are preceded by colourless substances known as “ chromogens,” which by the action of the oxygen of the air and by other agencies become changed into the corresponding pigments. In some cases the pigments are built up in the tissues of an animal, in others they appear to be derived more or less directly from the food. Derivatives of chlorophyll and lipochromes especially, seem to be taken up from the intestine, probably by the agency of leucocytes, in which they may occur in combination with, or dissolved by, fatty matters and excreted by the integument. In worms especially, the skin seems to excrete many effete substances, pigments included. Ho direct connexion has been traced between the chlorophyll eaten with the food and the haemoglobin of blood and muscle. Attention may, however, be drawn to the work of Dr Schunck, who has shown that a substance closely resembling haematoporphyrin can be prepared from chlorophyll; this is known as phylloporphyrin. Hot only does the visible spectrum of this substance resemble that of haematoporphyrin, but the invisible ultra-violet also, as recently shown by Mr C. A. Schunck. The reader may refer to Schafer’s Text-Book of Physiology (1898) for Gamgee’s article “On Haemoglobin, and its Compounds” ; to the writer’s papers in the Phil. Trans, and Proc. Roy. Soc. from 1881 onwards, and also Quart. Journ. Micros. Science and. Journ. of Physiol.) to Krukenberg’s Vergleichende physiologische Studien from 1879 onwards, and to his Vortrdge. Miss Newbigin has collected in Colour in Nature (1898) most of the recent literature of this subject. Dr Schunck’s papers will be found under the heading “Contribution to the Chemistry of Chlorophyll” in Proc. Roy. Soc. from 1885 onwards; and Mr C. A. Schunck’s paper in Proc. Roy. Soc. vol. Ixiii. (c. A. MacM.) Columbia, capital of Boone county, Missouri, U.S.A., situated in 38° 57' H. lat. and 92° 19' W. long., in the central part of the state, on the Wabash Railway, at an altitude of 783 feet. It is the site of the State University, and of Christian and Stephens Female Colleges. Population (1880), 3326; (1890), 4000; (1900), 5651. Columbia, a borough of Lancaster county, Pennsylvania, U.S.A., situated on the east bank of Susquehanna river, in the south-eastern part of the state, on branches of the Pennsylvania and the Philadelphia and Reading Railways, at an altitude of 251 feet. It has extensive manufactures, principally of iron. Population (1880), 8312; (1890), 10,599; (1900), 12,316. Columbia, capital of Richland county, South Carolina, U.S.A., and of the state, situated in 34° 00' H. lat. and 80° 57' W. long, on the east bank of Congaree river, at the junction of the Saluda and Broad, near the centre of the state, at an altitude of 244 feet.
