90 MAKITAL OF CATTLE-FEEDIKG. 



The source of tlie sugar in tliese cases is tlie glycogen of 

 the liver, which, bj some not well miderstood chemical 

 action, is converted into sugar. 



The same j)wcms takes place m tJte llvlny hody. The 

 blood in the portal vein of flesh-fed animals contains 

 no sugar, but the same blood in the hepatic vein, after 

 having passed through the liver, contains a notable quan- 

 tity of this substance^ doubtless derived from the glycogen 

 of the liver. 



These facts were discovered by Claude Bernard in 1853, 

 and are undisputed, but the source of the glycogen of the 

 liver, and its physiological significance, are questions upon 

 w^hich there is a diversity of opinion. Li w^hat follows 

 w^e shall endeavor to present in outline that view which 

 seems, on the w^hole, most probable, without, however, 

 treating the matter as one that is finally decided. 



"We have already called attention to the great quantity 

 of sugar that may be taken into the circulation in the 

 course of a few hours. This sugar is largely taken up by 

 the capillarieja of the stomach and intestines, and passes 

 by the portal vein into the liver, while in the general cir- 

 culation only traces of sugar are found. 



Putting these facts together, the conclusion seems almost 

 unavoidable that the liver has the power of converting 

 sugar into the insoluble glycogen and storing it up, to be 

 gradually reconverted into sugar as the needs of the organ- 

 ism demand. In other w^ords, the glycogen of the liver is 

 a rese)'V6 of carljhydrates. 



The functions of the carbhydrates in the body are, as 

 yet, but imperfectly understood, but there can be no doubt 

 that they play an important part in the animal economy. 

 According to some, the oxidation of these substances and 

 of fat furnishes a large shaie of the muscular and other 



