URINE-PIGMENT, 319 



pigment is in a state of constant change, that it is decomposed by 

 neutral and basic acetate of lead into two substances, differing in 

 their respective amounts of carbon and hydrogen; and that in a 

 healthy condition of the system it is poorer in these two elements 

 than when there are diseased conditions of the organism impeding 

 the pulmonary or cutaneous transpiration, or the secretion of bile. 

 That portion of the colouring matter which is richest in carbon, 

 forms, as has been found by Scherer and Heller,* a dark blue 

 powder, which when dried, possesses a coppery lustre similar to 

 indigo, and dissolves in alcohol with a splendid purple colour. 

 This latter variety of pigment is especially frequent in Bright's 

 disease. Heller distinguishes three such pigments, uroxanthin, 

 uroglaucin, and urrhodin. 



It is a matter of common experience in science generally, and 

 in chemistry more particularly, that the most circumstantial details 

 are given in reference to the more obscure and less investigated 

 departments, and that deficiencies of knowledge are concealed by 

 an enumeration of unconnected or inaccurately observed facts, or 

 by the most illogical deductions. For ourselves, however, we 

 prefer to confess our ignorance, and to spare our readers from the 

 accumulation of individual features which are incapable of afford- 

 ng a characteristic representation of the subject we would illustrate. 

 Chemists still reckon the urine-pigments amongst what they term 

 extractive matters, and may be said by this arrangement to make a 

 candid avowal of their ignorance in reference to these substances. 



Those who may be desirous of attempting to elucidate this 

 obscure subject experimentally, may derive considerable advantage 

 from the study of the older writings of Prout, Berzelius, and 

 Duvernoy, and the more recent memoirs of Heller and Scherer. 



EXTRACTIVE MATTERS. 



The above observations on the colouring or extractive matters 

 of the urine, lead us to the consideration of extractive matters in 

 general, and of those of the blood in particular. The term ex- 

 tractive matter is applied by chemists to those bodies which, 

 * Arch. f. Chem. u. Mikrosk. Bd. 2, S. 1C1 17^- 



