3 SS 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 of hydrobilirubin. 4 This pigment 
of the fieees 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 
hsematin, 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 lt3 H ls K,O ; 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 hand 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. 
- Jahrcsb. U. d. Fortschr. d. Thier-Chem., Wiesbaden, 1871, Bd. i. S. 80 ; Jlcd.-clum. 
UiUersvch., Berlin, 1871, S. 536. 
3 Ber. d. deutsch. chem. Gesellsch., Berlin, 1874, Bd. vii. S. 1065. 
4 Maly, Hermann's "HandbucV Bd. v. (2), S. 102. 
5 Jahresb. ii. d. Fortschr. d. Thier-Chem., AViesbaden, 1871, Bd. i. S. 229. 
6 Arch./, 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 ; Eichbolz, 
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. 
y SiLu/ujsb. d. k. Akad. d. V'iiscnsch., Wien, 1868, Bd. lvii. Abtb. 2, S. 107; 1869. 
Bd. lix. Abth. 2, S. 602. 
10 Hermann's "Handbuch " Bd. v. (2), S. 165. 
