THE BILE. 171 



free. If a moderate amount of a solution of haemoglobin is injected 

 into the bloodvessels of an animal, an increased elimination of 

 bilirubin results, while the blood-pigment does not appear in the 

 urine. If larger amounts are injected, the resulting bilirubin 

 apparently cannot be removed with sufficient rapidity through the 

 biliary ducts. Resorption of the pigment then takes place through 

 the lymph-vessels, jaundice results, and the bile-pigment appears in 

 the urine. If excessive amounts of haemoglobin finally are injected, 

 the liver is manifestly incapable of retaining all the pigment which 

 reaches the organ, jaundice results, and both the bile-pigment and 

 the blood-pigment appear in the urine. Even in such extreme 

 cases the remaining tissues of the body do not participate in the 

 formation of bilirubin. This has been conclusively demonstrated 

 by Minkowski and Naunyn. These observers have shown that while 

 in normal geese poisoning with hydrogen sulphide, which causes 

 an extensive dissolution of the red corpuscles, invariably leads to 

 jaundice and the appearance of bile-pigment in the urine, the 

 previous removal of the liver prevents such an occurrence, and 

 results in simple haemoglobinuria. In mammals such crucial tests 

 unfortunately cannot be applied, but there is no reason to suppose 

 that different conditions exist. The possible occurrence of a 

 hsematogenic icterus, in contradistinction to a hepatogenic icterus, is 

 thus rendered extremely improbable, and it is scarcely warrantable 

 to point to the development of bilirubin (haematoidin) from blood- 

 pigment in the tissues as indicating the possibility of such a trans- 

 formation in the circulating blood. 



Of the manner in which this transformation is effected in the liver 

 we know nothing. We may imagine, however, that the oxyhaemo- 

 globin is here first decomposed into its albuminous component 

 globin and into haematin, which latter, after loss of the iron, then 

 passes over into bilirubin, as shown in the equation : 



C 32 H 32 N 4 4 Fe + 2H 2 - Fe = C 32 H 36 N 4 O 6 

 Hsematin. Bilirubin. 



This reaction, it will be noted, is also supposod to express the 

 formation of haematoporphyrin from haematin (see Blood). The two 

 substances, indeed, are now quite generally regarded as isomeric, 

 especially since Kiister has shown that the haernatinic acids which 

 he obtained from bilirubin are identical with those resulting from 

 haematin, viz., haematoporphyrin (see Blood). As regards the size 

 of the molecule, however, opinions differ, and it is possible, as 

 Nencki and Sieber suppose, that the molecule of bilirubin, as well 

 as of haematoporphyrin, is only half as large as expressed above. 

 In that case, of course, the equation would have to be written : 



C 32 H 32 N 4 4 Fe + 2H 2 - Fe = 2C 16 H 18 N A. 



