THE LIVER. 161 



ered as proved. Independently, however, of this identity, which is 

 not admitted by all investigators, the view that the bile-pigments 

 are derived from the blood -coloring matters has strong arguments 

 in its favor. It has been shown by several experimenters (lately by 

 LATSCHENBERGER) that a yellow or yellowish-red coloring matter 

 can be formed from the blood-coloring matters which gives GMELIN'S 

 test, and which, though it may not form a complete bile-pigment, 

 is at least a step in its formation (LATSCHENBERGER). A further 

 proof of the formation of the bile-pigments from the blood-color- 

 ing matters consists in the fact that haematin yields urobilin, which 

 is identical with hydrobilirubin, on reduction (HoFPE-SEYLER). 

 Other investigators (NENCKI and SIEBER and LE NOBEL) claim 

 that the substance thus obtained is not true urobilin, but, all things 

 considered, it seems to be very nearly related. 



But even though the identity of urobilin with the hydro- 

 bilirubin obtained by the reduction of bilirubin is disputed by 

 certain investigators (MAcMuNK), still the substances may be so 

 closely related that the relationship will serve as a proof of the for- 

 mation of bilirubin from the blood-coloring matters. Further, 

 hsematoporphyrin (see page 78) and bilirubin are isomers, accord- 

 ing to NENCKI and SIEBER, and nearly allied. The formation of 

 bilirubin from the blood-coloring matters is shown, according 

 to the observations of several investigators, by the appearance of 

 free haemoglobin in the plasma by the destruction of the red 

 corpuscles by widely-differing influences (see below) or by the in- 

 jection of haemoglobin solution causing an increased formation of 

 bile-pigments. The amount of pigments in the bile is not only 

 considerably increased (TARCHANOFF), but the bile-pigments may 

 even pass into the urine under certain circumstances (icterus). 

 After the injection of haemoglobin solution into a dog either sub- 

 cutaneously or in the peritoneal cavity, GORODECKI observed in the 

 secretion' of pigments by the bile an increase of 60# which lasted for 



twenty hours. 



If, then, iron-free bilirubin is derived from the haematin con- 

 taining iron, then iron must be split off. This process may be 

 represented by the following formula, according to NENCKI 

 SIEBER, 



4 Fe + 2H 2 - Fe = 2C W H 18 N,0,, 



