338 THE ADRENAL, GENERAL MOTOR, AND VAGAL SYSTEMS. 



to, i.e., into the primary haemochromogen, which soon drops 

 its iron, leaving as end-product bilirubin. 



We have here the identical process that occurs in the brain 

 or other structures when blood-clots are disorganized into 

 hasmatoidin preparatory to absorption. "The bile-pigments 

 originate from haemoglobin 77 says Professor Howell; "this 

 origin was first indicated by the fact that in old blood-clots 

 or in extravasations there was found a crystalline product, the 

 so-called 'haematoidin/ which was undoubtedly derived from 

 haemoglobin, and which, upon more careful examination, was 

 proved to be identical with bilirubin. This origin, which has 

 since been made probable by other reactions, is now universally 

 adopted." That the influence of the suprarenal secretion rests 

 upon as solid a foundation is illustrated by the experiments 

 of Boinet, who found the blood of a large number of rats from 

 which he had removed the adrenals replete with "haematoidin." 



To trace the itinerary of the two products, iron and bili- 

 rubin, through the liver, naturally brings the hepatic cell 

 within the scope of our inquiry, since we have to account for 

 the transfer of the former to the bile and the return of the 

 iron to the general circulation. 



The functional importance of iron in the haemoglobin 

 molecule is generally recognized. Yet, the pigments, when 

 separated from it, are not unable to take up oxygen. Indeed, 

 we have ample evidence of this in the formulae of the very 

 products of which bilirubin is the primary compound. Thus, 

 while bilirubin is C 16 H 18 N 2 3 , biliverdin is C 16 H 18 N 2 4 , and 

 the latter can readily be prepared artificially from the former 

 by oxidation. "It is supposed that, when the blood-corpuscles 

 go to pieces in the circulation," says Howell, "the haemoglobin 

 is brought to the liver, and then, under the influence of the 

 liver-cells, is converted into an iron-free compound: bilirubin 

 or biliverdin. It is very significant to find that the iron sepa- 

 rated by this means from the haemoglobin is, for the most part, 

 retained in the liver, a small portion only being secreted in the 

 bile. It seems probable that the iron held back in the liver is 

 again used in some way to make new hcemoglobin in the haema- 

 topoietic organs." We have seen that it is not under the in- 

 fluence of the liver-cells, as now believed, that hcemoglobin is dis- 



