CHEMICAL BASIS OF THE ANIMAL BODY. 257 



also occasionally a fourth very faint band between the first two bands 

 described above. In alcoholic solution made alkaline by ammonia it 

 yields a spectrum closely resembling that of hsematoporphyrin (see 

 above p. 239). But unlike the latter substance its solutions show a 

 very faint green fluorescence on the addition of zinc chloride and 

 ammonia. The occurrence of hsematoporphyrin in urine has been 

 frequently recorded l and from the spectroscopic appearances described 

 above, some observers are inclined to the view that urohsemato- 

 porphyrin is not a single substance but a mixture of hsematoporphyrin 

 with some pigment closely resembling urobilin. 



Urohaematoporphyrin is perhaps closely related to two pigments known as 

 urorubrohaematin and urofuscoheematin obtained from a case of leprosy 2 (Mac 

 Munn). 



4. Humus pigments. 



When carbohydrates are treated with acids or alkalis, among 

 the numerous products which arise are certain pigmentary bodies 

 of a more or less dark brown colour. A similar colouration 

 is well known as occurring in fruits when bruised or exposed 

 to the air 3 , and generally in decaying vegetable tissues. These 

 substances are known under the name of 'humus.' When urine is 

 treated with acids in presence of oxygen it acquires a markedly darker 

 colour, and since carbohydrates in small amount are probably present 

 in all urines 4 , there is at once a possibility that some at least of the 

 observed colouration is due to the production of humus-pigmented 

 substances by the action of the acids on the carbohydrates. In 

 accordance with this view certain so-called humus pigments have been 

 prepared from urine, but our knowledge of them is as yet very incom- 

 plete. They are stated to be practically insoluble in any solvents other 

 than amyl-alcohol, strong ammonia and caustic alkalis : the solutions 

 show no absorption bands when examined spectroscopically. They are 

 further said to account for the usually dark colour of normal herbi- 

 vorous urine and of urine after the cutaneous absorption of carbolic acid 

 and several other aromatic compounds 5 . 



1 See most recently E. Salkowski, Zt. f. physiol Chem. Bd. xv. (1891), S. 286. 

 There was in the cases examined some evidence that the occurrence of hasmato- 

 porphyrin in the urine was perhaps not unconnected with the administration of 

 sulphonal. 



2 Baumstark, Ber. d. d. chem. Gesell. Bd. vn. (1874), S. 1170. Pfliiger's Arch. 

 Bd. ix. (1874), S. 568. Cf. Hoppe-Seyler, Physiol. Chem. 1879, S. 875. 



3 Hoppe-Seyler, Zt. f. physiol. Chem. Bd. xm. (1889), S. 66. 



4 See Wedenski, Ibid. S. 122. E. Salkowski, Ibid. S. 270. 



5 Udranszky, Ibid. Bde. xi. (1887), S. 537, xn. (1888), S. 33. Contains very full 

 references to other works. 



F. r 



