THE CARBOHYDRATES AND THEIR METABOLISM 257 



Endocrine and Nerve Control of Glycogenesis, Glycogenolysis and 



Glucolysis 



Influence of the sympathetic nervous system and of the adrenals. 



We now come to one of the most fascinating chapters in modern physi- 

 ology. Claude Bernard, in the middle of last century, found that by 

 puncturing the medulla, between the levels of origin of the vagus and 

 auditory nerves of animals, he was able to bring about glucosuria, which 

 was proven later to be the result of hyperglucemia. The intensity of 

 the reaction was found to be directly related to the nutritional condition 

 of the animal. Those that were well fed and contained a large amount 

 of glycogen in the liver reacted very strongly, showing hyperglucemia and 

 marked glucosuria ; those that were starved and contained little glycogen 

 in the liver reacted only feebly. 



In 1901 Blum made the very important discovery that the injection 

 of adrenalin was also followed by glucosuria, which was later proven to 

 be the result of hyperglucemia. The adrenalin glucosuria resembled the 

 puncture or piqtfre glucosuria, as it is called, in many respects. Its in- 

 tensity is also dependent upon the amount of glycogen in the liver, and 

 it also fails to produce hyperglucemia and glucosuria if the liver and 

 muscles are free from glycogen. 



It was further shown that repeated injections of adrenalin into animals 

 with large amounts of glycogen will ultimately result in a complete dis- 

 charge of all the glycogen from the liver. 



A more intimate view of the relationship of the above two funda- 

 mental discoveries, one may gather from an analysis of the work carried 

 out in Macleod's laboratory. First it was shown that by giving a sufficient 

 amount of nicotine to cause a complete blocking of the sympathetic ganglia, 

 the subsequent performance of the piqure experiment is followed by no 

 glucosuria, indicating that the sympathetic nerve fibers may be the car- 

 riers of the impulses to the liver. 



Secondly it was shown that by electrical stimulation of the great 

 splanchnic nerve on the left side a very marked hyperglucemia may be pro- 

 duced. 



It was further shown by G. N. Stewart that stimulation of the great 

 splanchnic nerve is followed by the appearance of marked and easily 

 detectable quantities of adrenalin in the blood of the suprarenal 

 veins. 



Lastly, it was shown by Mayer that after adrenalectomy in rabbits, 

 piqure produced no hyperglucemia nor glucosuria. 



From all the above, a chain of evidence seems to be established that, 

 piqure and adrenalin glucosuria are in reality one and the same kind of 

 stimulation to the liver, and as we shall see later, every gland of internal 

 secretion that possesses the power of sympathetic stimulation possesses 



