App.J CHEMICAL BASIS OF THE ANIMAL BODY. 767 



"alimentary canal, occurring in fbeces. There is no difficulty in seeing 

 how this change (hydrogenation) can be brought about in the intestine 

 since it is known that a considerable quantity of hydrogen may make 

 its appearance by fermentative processes in the intestine, and in its 

 nascent state might readily produce the simple change which is known 

 to occur when bilirubin is converted into hydrobilirubin. 



PIGMENTS OF URINE. 



Our knowledge of these bodies is at present limited and imperfect. 

 Most probably 1 they are numerous, but only two appear sufficiently well 

 characterised to deserve mention here. 



Urobilin . C 32 H^ N 4 O 7 . 



As stated above, this is now regarded as identical with hydrobilirubin. 

 It was first described by Jaffe 2 as a well-characterised normal urinary 

 pigment and its identity with hydrobilirubin subsequently determined 3 . 



Normal urine contains only small quantities of urobilin but there is 

 present a substance (chromogen) which under the influence of acids, 

 with absorption of oxygen, yields urobilin. The urine of fever fre- 

 quently contains a considerable amount of actual urobilin as such. 



The properties described above for hydrobilirubin are identical with 

 those of urobilin. Its preparation from urine is somewhat difficult and 

 for this some special manual must be consulted 4 . 



Uroerythrin 



Is considered to be the substance which gives to the urine of 

 rheumatism its characteristic colour. Yery little is known of its 

 chemical properties 5 . It appears to be an amorphous reddish body with 

 an acid reaction, slowly soluble in water, alcohol and aether. When 

 treated with caustic alkali it turns green. Urine containing this body 

 takes on a characteristic reddish-yellow colour on the addition of con- 

 centrated hydrochloric acid. 



Thudichum considers that normal urine contains only one pigment, which he calls 

 urochrome 6 . Maly is inclined to regard this as the same as urobilin 7 . More recently 

 Thndichum has upheld his former views 8 . 



1 Vierordt, Die quantitative Spectralanalyse, &c. Tubingen, 1876, S. 81. 



2 Centralb. f. d. med. Wis*. 1868, S. 243. Virchow's Arch. Bd. XLVII. (1869), 

 S. 405. 



3 Maly, Ann. d. Clitm..u. Pharm. Bd. CLXIII. (1872), S. 77. 



4 Vide Neubauer and Vogel. Harnanalyse, ed. vm. (1881), S. 81. 



5 Heller's Archiv. (2) Bd. in. (1854), S. 361. 



6 Brit. Med. Jl N. S., No. 201, 1864, p. 509. 



7 Maly, Ann. d. Chem. u. Pharm., loc. cit. 1872, S. 90. 



8 Jl. chem. Soc. Ser. 2. Vol. xin. (1875), pp. 397, 401. 



