GLYCOGEN AND ITS FORMATION. 349 



bile merely because its high oxygen constituent places it be- 

 yond the limits of further oxidation. Yet we have in another 

 component of bile, biliverdin, evidence that some oxidizing 

 process occurs during the passage of bilirubin through the 

 cell, under certain circumstances, perhaps when more oxidiz- 

 ing substance is present, for Howell says: "Biliverdin is sup- 

 posed to stand to bilirubin in the relation of an oxidation 

 product. Bilirubin is given the formula, C 16 H 18 !N" 2 03, and 

 biliverdin, C 16 H 18 N 2 4 , the latter being prepared readily from 

 pure specimens of the former by oxidation." 



With this evidence that oxidation does play some role 

 of the processes involved, it will facilitate our task to briefly 

 review the mutual relations of main biliary constituents. By 

 far the larger proportion of these is made up of the bile acids, 

 namely: the sodium salts of cholic acid, i.e., glycocholic and 

 taurocholic acid. These are obtained from cholic acid derived 

 itself from sugars and fats (Voit). Now, Tappeiner 21 found 

 that cholic acid yielded fatty acids on oxidation, and, since 

 taurocholic and glycocholic acids are fatty acids, this suggests 

 that they become such during their passage through the hepatic 

 cells and as the result of an oxidation process. 



The various phases of the process in the hepatic cells 

 become clear when the oxidizing substance is included as one 

 of the intrinsic factors involved. The blood-plasma of the 

 portal vein contributes the sugars and fats (along with the 

 waste-products to be excreted), while the hepatic artery sup- 

 plies plasma containing the oxidizing substance. All three 

 active agents meeting in the canaliculi, a part of the sugar 

 (according to the proportion of oxidizing substance present) 

 and all the fat (if the proportion of oxidizing substance is not 

 abnormally reduced by suprarenal insufficiency) are oxidized 

 into cholic acid. But, as the blood also contains glycocoll 

 (probably collagen-cartilage, mucin, connective tissue, and 

 gelatin-waste), glycocholic acid is formed. Again, since the 

 blood likewise contains taurin (probably muscle and pulmonary- 

 tissue waste), taurocholic acid is formed. Just the amount of 

 oxidizing substance necessary being supplied by the hepatic 



Tappeiner: Zeitschrift fttr Biologic, Bd. xii, S. 60, 1876. 



