136 Chapter IX 



Oxygen used 



Oxygen in c.c. per minute. 



Oxygen brought to liver by 



by the liver Portal vein Hepatic artery 



35 -85 -47 



41 '47 '82 



77 1-85 '59 



1-61 1-09 I'OO 



91 -66 3-00 



1-76 -66 2-06 



5-81 c.c. 5-58 c.c. 7'94 c.c. 



Indeed the oxygen used by the liver is unaffected if the portal 

 vein be ligatured altogether and its blood diverted into the general 

 circulation without first passing through the liver. So much for what 

 we may call the "resting" liver; by that we mean the liver of an 

 animal which had not been fed for 36 hours before the experiment. 



Important as is the arterial supply to the resting liver, it is much 

 more important in the case of the liver which is using up relatively 

 large quantities of oxygen. In animals which were fed 18 hours 

 before the experiment the quantities of oxygen brought to the liver 

 by the portal blood are of the same order as in those experiments 

 which we have already quoted ; the excess of oxygen brought comes 

 along the hepatic artery. From the following four experiments the 

 reader can gather the extent to which the liver would be starved of 

 oxygen did the hepatic artery perform no more important function 

 than that of supplying Glisson's capsule, and the walls of the blood 

 vessels and ducts. 



Oxygen used 



Oxygen in c.c. per minute. 



Oxygen brought to liver by 



by the liver Portal vein Hepatic artery 

 3-8 '28 3-53 



2-17 '58 1-56 



1-92 -78 3-67 



1-72 2-25 3-02 



9'61 c.c. 8-89 c.c. 11 '78 c.c. 



The mechanism by which the arterial supply of blood is increased 

 during digestion is unknown, it may be to some extent local and 

 to some extent reflex. This at least is known from the work of 

 Burton-Opitz (2 ' : the branches of the hepatic artery are richly sup- 

 plied by vaso-constrictor nerves; these have been denied to the 



