FORMATION OF SUGAR IN THE LIVER. 205 



blood. If a solution of glycogenic matter be mixed with fresh 

 human saliva, and kept for a few minutes at the temperature of 

 100 F., the mixture will then be found to have acquired the power 

 of reducing the salts of copper and of entering into fermentation by 

 contact with jeast. The glycogenic matter has therefore been 

 converted into sugar by a process of catalysis, in the same manner 

 as vegetable starch would be transformed under similar conditions. 



The glycogenic matter which is thus destined to be converted 

 into sugar, is formed in the liver by the processes of nutrition. It 

 may be extracted, as we have seen above, from the hepatic tissue 

 of carnivorous animals, and is equally present when they have been 

 exclusively confined for many days to a meat diet. It. is not in- 

 troduced with the food ; for the fleshy meat of the herbivora does 

 not contain it in appreciable quantity, though these animals so 

 constantly take starchy substances with their food. In them, the 

 starchy matters are transformed into sugar by digestion, and the 

 sugar so produced is rapidly destroyed after entering the circula- 

 tion ; so that usually neither saccharine nor starchy substances are 

 to be discovered in the muscular tissue. M. Poggiale 1 found that in 

 very many experiments, performed by a commission of the French 

 Academy for the purpose of examining this subject, glycogenic 

 matter was detected in ordinary butcher's meat only once. We 

 have also found it to be absent from the fresh meat of the bullock's 

 heart, when examined in the manner described above. Neverthe- 

 less, in dogs fed exclusively upon this food for eight days, glycogenic 

 matter may be found in abundance in the liver, while it does not 

 exist in other parts of the body, as the spleen, kidney, lungs, &c. 



Furthermore, in a dog fed exclusively for eight days upon the 

 fresh meat of the bullock's heart, and then killed four hours after 

 a meal of the same food, at which time intestinal absorption is 

 going on in full vigor, the liver contains, as above mentioned, both 

 glycogenic matter and sugar ; but neither sugar nor glycogenic mat- 

 ter can be found in the blood of the portal vein, when subjected to 

 a similar examination. 



The glycogenic matter, accordingly, does not originate from any 

 external source, but is formed in the tissue of the liver ; where it 

 is soon afterward transformed into sugar, while still forming a part 

 of the substance of the organ. 



The formation of sugar in the liver is therefore a function com- 



1 Journal de Physiologie, Paris,. 1858, p. 558. 



