CHAPTER VI. COLOURING MATTER-URÆMATINE. IN treating of the colour of urine as one of its physical characters, we have already made the distinction between the colouring matter of the urine proper, and those colouring principles which are accidental admixtures. Starting from the probability, in support of which we must give a few facts hereafter, that the normal colouring principle of urine is derived from the pigment of the blood or hæmatine, we have adopted the name of uræmatine; this denomination may be considered as corresponding to Heller's urophæine, and to a series of terms which were never generally introduced, and which it will therefore not be difficult to relinquish. The elementary composition of uræmatine is not yet ascertained, principally because no substance has as yet been found with which it would combine in unvariable proportions. But there are certain tests at present which promise to lead ultimately to a satisfactory analysis of this substance. The principal physical property of uræmatine is its colour. In a pure and dry state it is dark red; but when dissolved in alcohol and ether it is of a bright red, like port wine. To the urine it imparts all the varieties of colour with which we are acquainted; its presence in larger quantities will cause the deep tints, in small quantities the light tints, of that fluid, provided that the presence of abnormal pigments be out of the question. Chemical properties. Uræmatine combines with lime in uncertain proportions, and is separated from this combination by a mixture of alcohol and hydrochloric acid. It has a greater affinity for ether than for either alcohol or water. It is insoluble in nitric, hydrochloric, sulphuric, tartaric, and oxalic acids; soluble in ammonia, solutions of soda and of potash, and in chloroform. On combustion it leaves a small residue, consisting exclusively of oxyde of iron. By this fact its relation to hæmatine is satisfactorily established. It adheres with remarkable obstinacy to the salts of the urine, and therefore Berzelius applied to it the name of halophile. The following is Scherer's1 plan for isolating the uramatine: By adding a solution of basic acetate of lead to urine, a precipitate is obtained, which consists of lead, several acids of the urine, and a certain amount of colouring matter. The whole of the colouring matter cannot, however, be precipitated by the basic acetate, a circumstance which leads to the conclusion, that either the substance uræmatine consists in fact of two distinct bodies, or is decomposed by the influence of the basic acetate. The precipitate of the basic acetate of lead, when digested in alcohol acidulated by hydrochloric acid, yields lead to the acid and colouring matter to the alcohol, which latter on evaporation leaves the colouring matter as a blackish mass. The latter is freed from any acids by careful washing with water, in which it is insoluble. This insolubility shows that the substance must have undergone a change during the several operations for obtaining it in an isolated state. Another smaller quantity of colouring matter is precipitated by neutral acetate of lead. These precipitates, both with basic and neutral acetate of lead, contain from 6.25 to 8.83 per cent. of nitrogen, from 56 to 66 per cent. of carbon, and from 4·10 to 7.45 per cent. of hydrogen. These experiments of Scherer have been continued under his superintendence by Dr. G. Harley, who found that the precipitate of colouring matter with the basic acetate of lead could be separated into three or four constituents. But none of these matters have been obtained either crystallized, or in a certain combination with other known substances. They may therefore be the products of decomposition, and have at present no claim to be considered either as normal ingredients of the urine or as defined chemical entities. 1 'Med. Gazette,' 1845, pp. 363, 410. 2 Verhandl. des Würzburger Physic. Vereins,' Band v, 1854. Dr. Harley's method of obtaining uramatine is as follows: A large quantity of urine is evaporated to the consistence of molasses, the salts being removed from the fluid whenever crystallized. The residue is then extracted by alcohol. The latter is brought to a boiling heat, when milk of lime is added until all the colour has disappeared. The mixture is now filtered, when the combination of uræmatine with lime remains on the filter, and is washed out by means of ether and water. This compound, after having been dried, is digested in alcohol acidulated by hydrochloric acid; the alcoholic solution is filtered off, mixed with its volume of ether, and put aside for several days, during which time it must, however, be frequently shaken, in order to make the alcohol yield as much uramatine to the ether as possible. The ether and alcohol are then separated by the addition of water. The etherial solution, which has a fine colour of red wine, must now be washed with water, in order to free it from the traces of acid, salts, and resinous substances that may be dissolved in it. This washing must not be continued too long, because a little uræmatine is precipitated with every fresh quantity of water. The substance so obtained shows the properties above described. It is quite evident that such a method of analysis is not available for clinical purposes, or for quantitative researches. And as we have no other direct chemical analysis for uramatine which would at all come up to the modern requirements of chemistry, the indications of this ingredient of the urine are not easily to be determined. Happily, however, we possess a method, for which we are indebted to Professor Vogel, which enables us to estimate the quantity of uræmatine present in any urine with a tolerable degree of accuracy, and permits us to draw valuable conclusions regarding the diagnosis and prognosis of disease, and its therapeutical indications. It has been ascertained that a deeply coloured urine, when diluted with various quantities of water, will produce all the lighter tints of more frequent occurrence. From this it was reasonable to conclude that the various tints are only dilutions of one and the same description of colouring principle. Taking certain colours as starting points, a scale of tints was produced by mixing urine of the former colour with its equal volume of water. By this a tint was produced which was the next fixed point in the scale, and so on. These colours had to be expressed in material substances, for the purpose of Archiv des Vereins für gemeinschaftliche Arbeiten,' Bd. i, p. 137, 1853. procuring a standard which everybody might ascertain. The scale and its material representatives were therefore arranged as follows, and as is represented in the table affixed to the volume: I. FIRST GROUP. Yellowish Urines. The colour is yellow (gamboge), mixed with a greater or lesser amount of water. Starting with the perfectly colourless urine, this group has three gradations or nuances : 1. Pale yellow (gamboge with much water). 2. Light yellow (gamboge with less water). 3. Yellow (gamboge with very little water). II. SECOND GROUP. Reddish Urines. With the yellow there is mixed a greater or lesser amount of red (gamboge with crimson lake). These urines are generally termed "highly coloured." There are again three varieties of this group: 4. Reddish-yellow. An admixture of some red to the prevailing yellow (gamboge with a little crimson lake). 5. Yellowish-red. The red colour becomes more prominent in the yellow body of the fluid (gamboge with more crimson lake). 6. Red. The red colour is prevalent, but there is still a slight admixture of yellow (crimson lake with little gamboge). III. THIRD GROUP. Brown (dark) Urines. The red colour passes through brown to almost black tints. (gamboge, crimson lake, and more or less Prussian blue). 7. Brownish-red. brown. 8. Reddish-brown. than in the last. Red with an admixture of a little There is more of the brown colour 9. Brownish-black. Almost black, but with a touch of the reddish-brown. Though a delicate eye may yet distinguish several varieties of intermediate colours, yet the nine tints just described are all that are useful to be distinguished at the bedside. We now come to the determination of the unit in the corresponding varieties of urine. As the absolute quantity of uræmatine is not known which is required in a given bulk of urine to produce a certain colour, our unit must be a |