746 FORMATION OF BILIRUBIN. [BOOK n. 



in these cases has been urged by some as an argument that bili- 

 rubin is formed in the blood or at least elsewhere than in the liver 

 and is simply excreted by the liver. Not only however, as stated 

 above, is there no accumulation of bile in the blood after extirpation 

 of the liver, but that operation prevents the appearance of bilirubin 

 in the urine as a consequence of the presence of free haemoglobin 

 in the blood. The phenomena in question therefore do not 

 disprove that the bilirubin is formed in the liver; they may be 

 taken however to shew that that formation, viewed as a secretory 

 act, is peculiar, since the hepatic cell appears under certain circum- 

 stances to discharge its product of secretion into the blood or 

 lymph as well as into the bile passages. 



478. We may assume then that the hepatic cell has the 

 power of splitting up the haemoglobin brought to it, and of 

 discharging part as bilirubin while it retains for a time the iron 

 component in some organic combination ; and if we further assume 

 that it works upon the entire haemoglobin we may presume that 

 it makes some subsequent use of the proteid component. But are 

 we justified in assuming that the whole work is done by the 

 hepatic cells ? Are we to conclude that bilirubin is manufactured 

 by some act of the hepatic cells which includes not only the con- 

 version of haemoglobin into bilirubin, but also the extraction of 

 the haemoglobin from the red corpuscles as these are streaming 

 slowly through the lobular hepatic capillaries in close contact 

 with the hepatic cells? Now, as far as we know at present, 

 haemoglobin can only be set free by means of a disintegration 

 of the corpuscles ; we have no instances of a corpuscle parting 

 with some of its haemoglobin and proceeding on its way other- 

 wise unchanged ; and we have no histological evidence of any 

 disintegration of red corpuscles in the liver corresponding to the 

 formation of bile. Nor can we draw any conclusion from the 

 results of a comparative enumeration of red corpuscles in the 

 portal and hepatic blood, for these are too insecure to rest any 

 conclusion upon. On the other hand, as we have just seen, the 

 presence in the plasma of the blood of haemoglobin in a free con- 

 dition is peculiarly potent in exciting the formation of bilirubin. 

 The evidence therefore is very strong for the view that, as far as the 

 formation of the greater part at least of the bilirubin is concerned, 

 the action of the hepatic cell is limited to converting into bilirubin 

 the free haemoglobin offered to it by the portal blood. 



By what means, under normal conditions, is the presence of 

 that free haemoglobin secured ? We have seen reason ( 474) to 

 conclude from histological appearances that a certain number of 

 red corpuscles undergo change in the spleen pulp ; and it seerns 

 natural to infer that one duty of the spleen is to set free haemo- 

 globin from the corpuscles and thus, through the splenic veins and 

 so the portal vein, to supply the liver with material for bilirubin. 

 But this cannot be the only source, since the secretion of bile 



