462 SECRETION. 



this step of the operation has been satisfactorily performed, we have never found a trace 

 of sugar in the extract from the blood of the portal system, in animals that have been 

 fed upon nitrogenized matter alone. 



There can be no doubt that the blood carried to the liver by the portal vein does not 

 contain sugar, in animals fed solely upon nitrogenized matters. The quantity of blood 

 carried to the liver by the hepatic artery is insignificant ; and, although the arterial 

 blood may temporarily contain a trace of sugar, as we shall see farther on, this need not 

 complicate the question under consideration, as the presence of sugar in the blood of the 

 hepatic artery is exceptional, and its proportion, when it exists, is very minute. 



Examination of the Blood of the Hepatic Veins for Sugar. It is upon this question 

 that the whole doctrine of the sugar-producing function of the liver must rest. If it can 

 be proven that the blood, taken from the hepatic veins during life or immediately after 

 death, normally contains sugar, while the blood distributed to the liver contains neither 

 sugar nor any substance that can be immediately converted into sugar, the inevitable 

 conclusion is that the liver is a sugar-producing organ. We shall, consequently, examine 

 this part of the question with the care which its importance demands. 



The proposition that the blood from the hepatic veins does not contain sugar during 

 life and health cannot be sustained by actual experiment. Observers may say that the 

 quantity is very slight, but its existence in this situation, independently of the kind of 

 food taken, cannot be denied. Dr. Pavy, who is the originator of the theory that the 

 sugar found in the liver and in the blood coming from the liver is due to a post-mortem 

 change, nowhere states that he has taken the blood from the hepatic veins and failed to 

 find sugar. He says that he has found the blood taken from the right side of the heart 

 by catheterization, in a living animal, " scarcely at all impregnated with saccharine mat- 

 ter," but he does not deny its presence in small quantity. In twelve examinations made 

 by Dr. M'Donnell, of Dublin, traces of sugar were found in five specimens of blood taken 

 from the right auricle by catheterization, in the living animal, and no sugar was detected 

 in seven. It must be remembered, in considering these experiments, that the blood of 

 the right side of the heart is the mixed blood from the entire body ; and, assuming that 

 the hepatic blood is constantly saccharine, the quantity in the blood of the right heart 

 would not be very great. In opposition to these experiments, which are only partially 

 negative, we have the following results of examinations of the blood of the hepatic veins 

 and of the right side of the heart, taken as nearly as possible under normal conditions. 



To demonstrate the absence of sugar in the portal vein and its constant presence in 

 the hepatic veins in dogs fed exclusively upon meat, Bernard employed the following pro- 

 cess : The animal was killed instantly by section of the medulla oblongata. A small 

 opening was then made into the abdomen, just large enough to admit the finger and to 

 enable him to seize the portal vein as it enters at the transverse fissure and to apply a liga- 

 ture. The abdomen was then freely opened and a ligature was applied to the vena cava 

 just above the renal veins, to shut off the blood from the posterior extremities. The chest 

 was then opened, and a ligature was applied to the vena cava just above the opening of the 

 hepatic veins. Operating in this way, blood may be taken from the portal system before 

 it enters the liver, and from the hepatic veins as it passes out. In the blood from the 

 portal system no sugar is to be found, but its presence is unmistakable in the blood from 

 the hepatic veins. To avoid disturbing the circulation in the liver, and in order to col- 

 lect from the hepatic veins as large a quantity of blood as possible, Bernard modified the 

 experiment, in some instances, by introducing into the vena cava in the abdomen a 

 double sound, the extremity of which is provided with a bulb of India-rubber. This 

 was pushed into the vein above the diaphragm ; and, by inflating the bulb, the vein was 

 obstructed above the liver, and the blood could be collected through one of the canulao, 

 as it came directly from the hepatic vessels. Bernard never failed to determine the 

 presence of sugar in these specimens of blood, employing a number of different pro- 

 cesses, including the fermentation-test and even collecting the alcohol. To complete 



