BILE PIGMENTS AND THEIR DERIVATIVES. 389 



The halogens react energetically with bilirubin, forming substitution 

 products. When bromine acts on bilirubin, a series of changes in colour 

 take place, exactly counterfeiting those observed in Gmelin's reaction. 

 The reactions are, however, quite different ; and the process is not, as one 

 might naturally have expected, an oxidation, but a substitution of 

 bromine for hydrogen 1 (2C 16 H 18 N 2 3 +3Br 2 = C 32 H 33 Br 3 N 4 O 6 +3HBr). 2 



The reaction is best shown by adding a dilute solution of bromine in 

 chloroform, cautiously, to a solution of bilirubin, also in chloroform. The solu- 

 tion changes through green, blue, and red into yellow, as the bromine is added, 

 and may be stopped and examined at any stage. If chloroform free from 

 alcohol be used, a tribromo derivative separates out of solution. Decanted 

 from chloroform, dissolved in alcohol, and reprecipitated by adding water, this 

 compound is obtained as a dark blue powder, soluble in alcohol, in ether, or 

 in chloroform containing alcohol ; but insoluble in pure chloroform, or in 

 water. Alkalies split it up, yielding biliverdin. 



Nothing is known of the chemical constitution of the bile pigments, 

 and very little of the intermediate stages in their production from 

 haemoglobin. Their connection with haemoglobin rests on (1) The 

 identity of haematoidin produced in old blood clots with bilirubin. (2) 

 The identity of Hoppe-Seyler's reduction product obtained from haematin, 

 and thus indirectly from haemoglobin, with Maly's hydrobilirubin. 



(3) The absence of bile pigments in such animals as have no haemoglobin. 3 



(4) The fact that anything causing increased destruction of red blood 

 corpuscles, or the intravenous injection of haemoglobin, causes an increased 

 secretion of bile pigments. 4 (5) Haematoporphyrin is isomeric with 

 bilirubin, shows with nitric acid colour changes somewhat resembling 

 Gmelin's reaction, and yields on reduction with nascent hydrogen a 

 substance closely resembling and probably isomeric with hydrobilirubin. 

 According to Nencki and Sieber, 5 bilirubin is formed in the liver by the 

 haemoglobin first splitting up into haematin and proteid. The haematin 

 thus formed then takes up water, loses its iron, which is retained in 

 combination in the liver, and so forms bilirubin, thus 



C 32 H 32 N 4 4 Fe-f 2H 2 Fe = C 32 H 36 N 4 6 ; or 2(C 16 H 18 N 2 3 ) 



(hsematin) (bilirubin) 



Direct experiments on the formation of bile pigments from haemo- 

 globin apart from the liver have been carried out by Latschenberger. 6 

 If the corpuscles and serum of horse blood be separately injected sub- 

 cutaneously at different parts in the horse, and after the lapse of about 

 twelve days the animal be killed, and the parts where the injections have 

 been made are examined, it is found that while, at the part where the 



1 Thudichum, Journ. Chem. Soc., London, 1875, vol. xxviii. p. 389 ; Maly, Sitzungsb. d. 

 k. Akad. d. Wissensch., Wien, Bd. Ixxii. Abth. 2. 



2 Maly, Hermann's "Handbuch," Bd. v. (2), S. 167. 



3 Hoppe-Seyler, Arch. f. d. ges. Physiol., Bonn, 1877, Bd. xiv. S. 399. See, however, 

 Krukenberg, CentralU. f. d. med. Wissensch., Berlin. 1883, No. 44, S. 785. 



4 Frerichs, Arch. f. Anat. u. PhysioL, Leipzig, 1856, S. 59 ; W. Kiihne, Virchow'sArchiv, 

 1858, Bd. xiv. 8. 310 ; Nothnagel, BerL klin. Wchnschr., 1866, vol. vi. S. 31 ; Tarchanoff, 

 Arch. f. d. ges'. PhysioL, Bonn, 1874, Bd. ix. S. 329 ; Minkowski and Bassorin, Arch. f. 

 exper. Path. u. Pharmakol., Leipzig, 1887, Bd. xxiii. S. 145. 



5 Ber. d. deutsch. chem. Gesdlsch., Berlin, 1884, Bd. xvii. S. 2275 ; Monatsh. f. Chem., 

 Wien, 1888, Bd. ix. S. 115 ; Arch. f. exper. Path. u. Pharmakol., Leipzig, 1888, Bd. xxiv. 

 S. 430. 



6 Monatsh. f. Chem., Wien, 1888, Bd. ix. S. 52; Sitzungsb. d. k. Akad. d. Wissensch., 

 Wien, 1888, Bd. xcvii. Abth. 2b, S. 15. 



