300 PHYSIOLOGY CHAP. 



the intestine after digestion is stored up in the liver : the second 

 that the liver returns the accumulated sugar to the blood by 

 internal secretion. 



Thus we are brought back to the Liver, that giant gland which 

 we considered in the last chapter merely as the organ of bile 

 secretion, while admitting this to be neither the principal nor the 

 most important of its functions. 



Magendie (1816) was the first who demonstrated experimentally 

 that the system of intestinal veins which form the roots of the 

 portal system, and to which Bichat drew the attention of 

 physiologists, is capable of absorbing the substances introduced 

 into the intestine a fact denied by John Hunter. One of 

 Magendie's crucial experiments was as follows : 



He tied all the lymphatics of a loop of intestine isolated 

 between two ligatures; next, he tied all the arteries and veins 

 with the exception of one artery and vein, of which he removed 

 the adventitia for a certain distance to make sure that no lymph 

 vessel had been left ; lastly, he injected a decoction of nux vomica 

 into the loop. After 6 minutes, strychnine poisoning set in with 

 great intensity, showing that absorption had taken place through 

 the roots of the only intestinal vein remaining. The later experi- 

 ments of Se"galas and of Tiedemann and Gmelin, confirmed 

 Magendie's results, and established the importance of the 

 intestinal veins in intestinal absorption. 



But it was Claude Bernard who fully vindicated the claims of 

 the liver, which Bartholin had disallowed. In 1849 he announced 

 that animals, like plants, have the power of forming sugar 

 independent of the nature of the food, and that this new function 

 resides in the liver, which is therefore the seat of a double secretion ; 

 the one external, of bile ; the other internal, of sugar. 



In studying the course of the ingested sugar, as it passes 

 through the body, Bernard sought for it in the venous blood 

 coming from the right heart and the arterial blood coming from 

 the left carotid, on the assumption that it was decomposed by the 

 lungs. He observed that the blood of the right heart contained 

 sugar, not only when it was extracted from a dog fed on sugar, 

 but also when the animal was kept on a flesh diet. From this he 

 concluded that there must be an organ in the body capable of 

 forming sugar, independent of what was ingested, and that this 

 organ was the liver, because extract of liver was able to reduce 

 Bareswill's reagent and gave rise to alcoholic fermentation, which 

 did not occur with extracts of the other organs. 



In order to demonstrate that the liver really manufactures 

 sugar during its life, it was necessary to prove that the blood 

 flowing from the liver contained more sugar than the blood which 

 entered it. In 1850 Schiff, who found a certain amount of sugar 

 in human blood, and in that of animals from the slaughter-house, 



