3 88 CHEMISTR Y OF THE DIGESTIVE PROCESSES. 



pigment, already described under the name of urobilin, and discovered 

 by Jaffe l under pathological conditions in the urine. Immediately 

 before Maly's discovery, Hoppe-Seyler 2 had described a brownish-red 

 substance, which he obtained by the action of zinc and hydrochloric 

 acid (i.e. nascent hydrogen), on haematin ; this, he afterwards stated to 

 be impure hydrobilirubin. 3 When one considers that bilirubin is poured 

 into the intestine with the bile, and that it is here subjected to reducing 

 influences, as is shown by the frequent presence of hydrogen in the 

 intestinal gases, it is natural to suppose that a considerable conversion 

 of bilirubin into hydrobilirubin goes on in the intestine. The pigments 

 of the faeces, which must arise mainly from the bile pigments, do not 

 give Gmelin's reaction; extraction of the faeces with dilute spirit, 

 evaporating and extracting the residue with strong spirit, yields a 

 solution which shows the spectrum ?f hydrobilirubin. 4 This pigment 

 of the faeces had been already described as stercobilin by Vanlair and 

 Masius. 5 Jaffe 6 considered it as identical with his urobilin. Maly 

 gives the above theory of its formation in the intestine from bilirubin, 

 and looks upon all three, as well as Hoppe-Seyler's compound from 

 haamatin, as one substance, namely, hydrobilirubin. 7 



It is generally accepted that these substances are closely related, if 

 not identical, and their relationship is of the utmost importance in con- 

 necting the pigments of the bile with the waste products of haemoglobin. 8 



Choletelin. Besides this important reduction derivative of bilirubin, 

 we also owe to Maly 9 the discovery of choletelin, the final substance 

 obtained in its oxidation by nitric acid. 



At the end of the reaction a yellow colour is obtained, not widely 

 different from that of the bilirubin from which the reaction started; 

 when this condition is reached, all the intermediate products have been 

 converted by oxidation into one substance. 



Choletelin is best prepared, according to Maly, 10 by leading a stream of 

 nitrous fumes (prepared by acting on arsenious acid with nitric acid) through 

 bilirubin suspended in alcohol. The fluid passes through the colours of 

 Gmelin's reaction, and finally a clear, pale, yellowish-red solution is left ; this 

 is thrown into water, when choletelin separates out in rust-coloured flocks, 

 which form, when dried, a brown powder. Choletelin is amorphous and 

 probably represented by the formula C 1G H 18 N 2 6 ; it is soluble in alcohol, 

 ether, chloroform, and acetic acid. It is also soluble in alkalies, and 

 precipitated from such solution by acids. In acid solution it shows a dim 

 absorption band lying between b and F, and corresponding to the band y 

 observed by Jaffe in solutions of bilicyanin. In neutral alcoholic solution this 

 band disappears. 



1 Virchow's Archiv, 1869, Bd. xlvii. S. 405-418. 



2 Jahresb. ii. d. Fortschr. d. Thier-Chem., Wiesbaden, 1871, Bd. i. S. 80 ; Med.-chem. 

 Untersuch., Berlin, 1871, S. 536. 



3 Ber. d. deutsch. chem. Gesellsch., Berlin, 1874, Bd. vii. S. 1065. 



4 Maly, Hermann's "Handbuch," Bd. v. (2), S. 162. 



5 Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1871, Bd. i. S. 229. 



6 Arch.f. d. ges. PhysioL, Bonn, 1871, Bd. iv. S. 537. 



7 Hermann's "Handbuch," Bd. v. (2), S. 162. 



8 See MacMunn, Journ. PhysioL, Cambridge and London, 1889, vol. x. p. 71 ; Eichhok, 

 Journ. PhysioL, Cambridge and London, 1893, vol. xiv. p. 326 ; Garrod and Hopkins, 

 Journ. PhysioL, Cambridge and London, 1896, vol. xx. p. 113 ; Garvoch, ibid., 1897, vol. 

 xxi. p. 190. 



9 Sitzungsb. d. k. Alcad. d. Wissensch., Wien, 1868, Bd. Ivii. Abth. 2, S. 107 ; 1869. 

 Bd. lix. Abth. 2, S. 602. 



10 Hermann's "Handbuch " Bd. v. (2), S. 165. 



