PRODUCTION OF SUGAR IN THE LIVER. 459 



positively conclusive in their results, excited the most profound scientific interest. Dur- 

 ing the present century, indeed, there have been few physiological questions that have 

 attracted so much attention ; and the observations of Bernard were soon repeated, 

 modified, and extended by experimentalists in different parts of the world. In 1857,' 

 Bernard discovered a sugar-forming material in the liver, analogous in its composition 

 and properties to starch ; and this seemed to complete the history of glycogenesis. 



Shortly after the publication of the glycogenic theory, it was found that other changes 

 were effected in the blood in its passage through the liver ; and physiologists then under- 

 stood, for the first time, how glandular organs might produce secretions and yet not dis- 

 charge them into excretory ducts. This, indeed, pointed the way to the explanation 

 of the function of the ductless glands. It is perfectly correct to say that the liver 

 secretes sugar ; but the secretion, in this instance, is carried away by the blood, and, from 

 this point of view, the liver is to be regarded as a ductless gland. It is evident, there- 

 fore, that, even after having studied fully the secretion and the physiological relations of 

 the bile, we have to consider other glandular functions of the liver which are hardly less 

 important. 



Evidences of a Glycogenic Function in the Liver. The proof of the glycogenic func- 

 tion of the liver rests upon the fact, experimentally demonstrated by Bernard, that, in 

 all animals, the blood coming from the liver by the hepatic veins contains sugar, and 

 that the presence of this principle here is not dependent upon the starch or sugar of 

 the food. Bernard assumes to have proven that, in carnivorous animals, never having 

 taken starch or sugar into the alimentary canal except in the milk, there is no sugar in 

 the blood of the portal vein as it passes into the liver ; but, under normal conditions, the 

 blood of the hepatic veins always contains sugar. Having examined the blood from vari- 

 ous parts of the body and made extracts of all the other tissues and organs, Bernard was 

 unable to find sugar in any other situations than in the liver and the blood coming from 

 the liver. As the blood from the liver is mixed in the vena cava with the blood from the 

 lower extremities, and in the right side of the heart, with the blood from the descending 

 cava, the amount of sugar is proportionately diminished in passing from the liver to the 

 heart. It was found that the sugar generally disappeared in the lungs and did not exist 

 in the blood of the arterial system. Assuming that these statements have been sustained 

 by experimental facts, there can be no doubt that the liver produces or secretes sugar, 

 that this secretion is taken up by the blood, and that the sugar is destroyed in its pas- 

 sage through the lungs. 



The question of the production of sugar in the economy has given rise to a great deal 

 of discussion, and the experiments of Bernard have been repeated very extensively. 

 Many physiologists of high authority have been able to verify these observations in every 

 particular ; but others have published accounts of experiments which seem to disprove 

 the whole theory. 



There can be no doubt of the fact that sugar may, under certain conditions, be pro- 

 duced de novo in the organism. Cases of diabetes, in which the discharge of sugar by the 

 urine continues, to a certain extent, when no starch or sugar is taken as food, are conclu- 

 sive evidence of this proposition. It is a fact equally well established, that the sugar 

 taken as food and resulting from the digestion of starch is consumed in the organism 

 and is never discharged. The fact with regard to diabetes shows, then, that it is not 

 impossible, when no sugar or starch is taken as food, that sugar should be produced in 

 the body ; and the failure to find the sugar of the food in the blood or excreta shows 

 that this principle is normally destroyed or consumed in the organism. It only remains, 

 therefore, to determine whether the production of sugar in diabetes be a new pathologi- 

 cal process or merely the exaggeration of a physiological function. 



We have so often repeated and verified the observations of Bernard, both in experi- 

 ments made for purposes of investigation and in public demonstrations, that we can 



