718 FKANCIS H. McCKUDDEN 



(a) Jan. 3, 0.145 per cent July 5, 0.1^7 per cent. 



(b) Aug. 20, 0.159 per cent Aug. 23, 0.159 per cent. 



(c) Dec. 17, 0.095 per cent Dec. 30, 0.092 per cent 



This concentration of blood sugar one tenth of one per cent is stub- 

 bornly maintained throughout prolonged starvation, almost up to death 

 Allen (a)). This is to be attributed to the tenacity with which the organs 

 maintain a glycogen reserve. After fasting twelve days and excreting 

 large amounts of sugar in the urine, as a result of phlorizin injection, the 

 body still contains glycogen (Prausnitz). Even after seventy-three days' 

 starvation, glycogen is still found in the body (Pfliiger(s)). The heart 

 is known to maintain its normal glycogen content after fifteen days of 

 starvation (Jensen, Kulz(rf)). 



Under normal conditions the blood sugar in the general circulation 

 does not diminish to any great extent as a result of muscular activity, 

 the normal level of approximately one-tenth of one per cent being main- 

 tained by the influx of glucose derived from the glycogen stored in the 

 body, and from the carbohydrate (and carbohydrate-forming substances) 

 in the food. As glucose passes into the blood stream from the gastro- 

 intestinal tract, the concentration of glucose in the blood rises. But the 

 rise is not very great, scarcely ever to above 0.12 per cent; the excess is 

 quickly changed to glycogen and stored, chiefly in the liver, to a less extent 

 in the muscles and other organs. There are then two opposing tendencies : 

 one, muscular activity tending to diminish the concentration of blood 

 sugar ; and the other, the absorption of glucose from the gastro-intestinal 

 tract, tending to increase the blood sugar. Standing between these two 

 opposing tendencies, as a buffer to prevent any wide deviation of the glu- 

 cose of the blood from the normal of one-tenth per cent, is the glycogenesis- 

 glycogenolysis mechanism. 



Many organs take part in controlling the concentration of sugar in the 

 blood : the liver, muscles, pancreas, kidney, nervous system, adrenals and 

 other organs of internal secretion. And the blood sugar can bealtered 

 by pathological changes in these organs. 'The immediate supply of blood 

 glucose is provided chiefly by the glycogen stored in the liver. If the liver 

 is poisoned by phosphorus its power to store glycogen becomes damaged, 

 and the concentration of glucose in the blood may fall. Adrenalin has 

 something to do with regulating the blood sugar concentration. Blood 

 sugar may be increased by injection of adrenalin ; the adrenalin increases 

 the rate of glycogenolysis in the liver. Conversely, when the adrenals are 

 damaged or removed, the glycogenesis-glycogenolysis functions of the liver 

 become damaged and the blood sugar falls. The thyroid and pituitary 

 glands have some similar relationship to these liver functions ; administra- 

 tion of thyroid or pituitary gland increases the blood sugar ; and after thy- 

 roidectomy the capacity of the heart to utilize glucose is diminished 



