444 VICTOE C. MYEKS 



of the other methods. That the reducing power of the blood is due in 

 large part to glucose seems certain, although the various methods appear 

 to be influenced by other reducing substances. Of the known interfering 

 substances creatinin is the most often mentioned. In normal blood, how- 

 ever, it probably does not introduce an error of more than 2 or 3 per cent. 

 Although the question of the actual content of glucose in normal blood is 

 one of great theoretical interest and importance, the figures obtained by 

 the various methods differ so little relative to the variations which occur in 

 disease that the question of the method scarcely enters into a discussion of 

 blood sugar findings in disease. 



The figure of 0.10 per cent for normal individuals given above applies 

 to observations made in.the morning previous to the intake of any carbo- 

 hydrate. After a meal rich in carbohydrate there may be an appreciable 

 rise in the sugar content of the blood, 0.12 to 0.14 per cent, while after 

 the intake of even moderately "large amounts of glucose, the hyperglycemia, 

 0.15 to 0.16 per cent, may be sufficient to induce a slight temporary (gly- 

 cosuria) glycuresis. The great majority of hospital cases show practically 

 normal figures for blood sugar, although occasionally figures of 0.12 to 0.15 

 per cent are encountered that are not readily explained. 



Conditions of hyperglycemia are much more common and of greater 

 clinical interest than those of hypoglycemia, owing primarily to the fact 

 that diabetes belongs to the former group. Among other conditions which 

 frequently show moderate hyperglycemia are pancreatic disease, nephritis 

 and hyperthyroidism. Hypoeiidocrin function would appear to result in 

 hypoglycemia, and comparatively low blood sugars have been observed in 

 myxedema, cretinism, Addison's disease, pituitary disease and other less 

 clearly defined endocrin conditions such as muscular dystrophy. 



All forms of glycosuria are accompanied by hyperglycemia, if we 

 except the glycosuria produced by such substances as phlorhizin and urani- 

 um, and the analogous condition, "renal diabetes." In mild cases of dia- 

 betes the hyperglycemia is not excessive, generally 0.2 to 0.3 per cent, al- 

 though in severe cases figures up to and even above 1.0 per cent have been 

 obtained. The normal threshold of sugar excretion (i. e. ; the point of 

 glycuresis) is about 0.16 to 0.18 per cent. With blood sugar concentrations 

 of 0.15 to 0.20 per cent the appearance of sugar in the urine is apparently 

 dependent on whether or not diuresis exists, glycosuria appearing especial- 

 ly in the latter case. When the threshold point has been passed, however, 

 the overflow of sugar into the urine may continue until the concentration 

 in the blood has fallen nearly to normal. Mild cases of diabetes usually 

 have a normal threshold, although some severe cases apparently have a 

 lowered threshold, increasing the severity of the condition. Ordinarily 

 in the early stages of the disease there is a fairly direct relationship be- 

 tween the hyperglycemia and glycosuria. In the later stages of the disease, 

 however, cases are frequently encountered with marked hyperglycemia and 



