GLYCOGEN STORAGE BY THE LIVER 37 



owing to constriction of the bloodvessels of the abdominal 

 organs. Section of the cord resulting in loss of vascular tone 

 and general fall of blood pressure and velocity decreases the 

 secretion. Stimulation of the splanchnics which have been 

 cut diminishes secretion, owing to vascular constriction of 

 the abdominal organs, while sectioning alone increases the 

 secretion, since the resulting loss of vascular tone is limited 

 to the abdomen, resulting in a greater flow of blood to that 

 region. The determination of distinct secretory fibers for the 

 formation of bile has so far been impossible. 



A more important stimulus to bile secretion is secretin. 

 The activity of the liver parallels that of the pancreas, so that 

 it too manifests a definite relation to the digestion of food. 

 This depends upon the amount of chyme passed into the 

 duodenum, for in this way is determined the amount of secretin 

 formed and the time of its formation. In the case of fats a 

 further adaptation follows from the absorption of bile salts, 

 which accompanies the absorption of fatty acids and soaps 

 formed during fat digestion. 



The pressure under which bile is secreted is at the most 

 25 mm. Hg, so that but a slight obstruction, an inflammation 

 of the bile duct or a biliary calculus, leads readily to jaundice. 



Formation of Urea by the Liver. Urea, which is the main 

 end product of protein metabolism, is formed, in part, at least, 

 not in the kidney which excretes it, but in the liver. If an 

 isolated liver is perfused with blood taken from a recently 

 fed dog, the urea contained in it is increased. This is not the 

 case when the blood from a fasting animal is used. The blood, 

 therefore, after digestion contains something that can be 

 converted to urea. Ammonium carbonate is promptly con- 

 verted to urea if added to the perfusing blood. If the liver 

 is separated from the circulation by the establishment of an 

 Eck fistula, there follows a diminution in the amount of urea 

 in the urine and an increase in the ammonia compounds. It 

 has been shown that the portal vein possesses three or four 

 times as high an ammonia content as arterial blood. Pre- 

 sumably ammonia compounds of the portal blood are converted 

 to urea in passing through the liver. 



Glycogen Storage by the Liver. Glycogen has the general 

 formula of vegetable starch (G 6 H 10 O 5 ) n . With iodine it gives 



