CAPILLARY ATTRACTION, ETC. [MEMOIR XXVI. 



compounds of carbon and hydrogen with soda are sepa- 

 rated as bile, and pass along the biliary tubes. In its 

 final effect, therefore, the chemical action of the liver close- 

 ly resembles the chemical action of the lungs. Compared 

 with the blood which passes along the branches of the 

 hepatic veins and finds its way into the ascending vena 

 cava, the portal blood differs by containing the elements 

 of bile. 



Two systems of forces now conspire to drive the por- 

 tal blood out of the liver into the ascending cava. 



First, the blood which is coming along the capillary 

 portal veins and that which is receding by the hepatic 

 veins, compared together as to their affinities for the 

 substance of the liver, obviously have this relation : the 

 portal blood is acted upon by the liver, and there are 

 separated from it the constituents of the bile ; the affin- 

 ities that have been at work in producing the result 

 have all been satisfied ; and the residual blood, over 

 which the liver can exert no action, constitutes that 

 which passes into the hepatic veins. Between the por- 

 tal blood and the substance of the liver there is an ener- 

 getic affinity, indicated by the circumstance that a chem- 

 ical decomposition takes place and bile is separated ; but, 

 that change once completed, the residue, which is no 

 longer acted upon, forms the venous blood of the he- 

 patic veins, and hence the portal blood drives before it 

 the inert blood which is in those veins. 



But, in addition to this, the blood of the hepatic ar- 

 tery, after serving for the economic purposes of the liver, 

 is thrown into the portal plexus. Hence arises a second 

 force, which, conspiring in its resultant with the former, 

 produces movement in the same direction. The pres- 

 ence of the arterial blood in the hepatic capillaries is not 

 only sufficient to give a force towards that in the capil- 

 laries of the portal veins, but also to give it a pressure 



