VARIATIONS IN THE GLYCOGENIC FUNCTION. 469 



carnivora and herbivora ; and, although its quantity may be modified by the kind of food, 

 its formation is essentially independent of the alimentary principles absorbed. 



The glycogenic matter is not taken up by the blood as it passes through the liver, but 

 is gradually transformed, in the substance of the liver, into sugar, which is washed out 

 of the organ as fast as it is produced. Thus the blood of the hepatic veins always con- 

 tains sugar, although sugar is not contained in the substance of the liver during life. 



Variations in the Glycoyenic Function. 



In following out the relations of the glycogenic process to the various animal func- 

 tions, Bernard studied very closely its variations at different periods of life, with diges- 

 tion, the influence of the nervous system, and other modifying conditions. He made 

 some of his observations by examining the blood in living animals, and others, by esti- 

 mating the proportion of sugar in the liver. The latter method is to be considered, with 

 an appreciation of the fact that the liver does not normally contain sugar during life ; 

 but it represents, to a certain extent, the activity of the glycogenic function. Still, the 

 facts arrived at in this way must be taken with a certain degree of caution. 



Glycogenesis in the Foetus. In the early months of foetal life, many of the tissues 

 and fluids of the body were found by Bernard to be strongly saccharine ; but at this 

 time no sugar is to be found in the liver. Taking the observations upon foetal calves as 

 a criterion, sugar does not appear in the liver until toward the fourth or filth month of 

 intra-uterine life. Before this period, however, epithelial cells filled with glycogenic 

 matter are found in the placenta, and these produce sugar until the liver takes on its 

 functions. As the result of numerous observations by Bernard upon foetal calves, this 

 function of the placenta appears very early in foetal life, and, at the third or fourth 

 month, it has attained its maximum. At about this time, when glycogenic matter begins 

 to appear in the liver, the glycogenic organs of the placenta become atrophied, and they 

 disappear some time before birth. 



Influence of Digestion and of Different Kinds of Food. Activity of the digestive 

 organs has a marked influence upon the production of sugar in the liver. In a fasting 

 animal, sugar is always found in the blood of the hepatic veins and in the vessels between 

 the liver and the heart, but it never passes the lungs and does not exist in the arterial 

 system. During digestion, however, even when the diet is entirely nitrogenized, the 

 production of sugar is so much increased that a small quantity frequently escapes decom- 

 position in the lungs and passes into the arterial blood. Under these conditions, the 

 quantity in the arterial blood is sometimes so large that a trace may appear in the urine, 

 as a temporary and exceptional, but not an abnormal condition. This physiological fact 

 is well illustrated in certain cases of diabetes. There are instances, indeed, in which the 

 sugar appears in the urine only during digestion ; and, in almost all cases, the quantity 

 of sugar eliminated is largely increased after eating. 



The influence of the kind of food upon the glycogenic function is a question of great 

 pathological as well as physiological importance. It is well known to pathologists that 

 certain cases of diabetes are relieved when the patient is confined strictly to a diet con- 

 taining neither saccharine nor amylaceous principles, and that, almost always, the quan- 

 tity of sugar discharged is very much diminished by such a course of treatment; but 

 there are instances in which the discharge of sugar continues, in spite of the most care- 

 fully-regulated diet. Bernard does not recognize fully the influence of different kinds of 

 food upon glycogenesis, and his experiments on this point are wanting in accuracy, from 

 the fact that the proportion of sugar in the liver is given, without indicating at what 

 period after death the examinations were made. In the observations upon this point by 

 Pavy, the examinations of the liver were made immediately after death, and the propor- 

 tion of glycogenic matter not sugar was estimated. His results are, consequently, much 



