THE ABSORPTION AND USE OF FOODS 495 



into the general circulation. Should this excess be sufficient to 

 raise the sugar percentage of the blood above 0.2 per cent there is 

 excretion of sugar from the kidney, a condition known as gly- 

 cosuria. It is found that the rate of absorption of sugar depends 

 chiefly on how much of it is present at one time in absorbable 

 form in the intestine. Thus if large amounts of single sugar are 

 eaten the essential condition for excessive absorption is likely to 

 be fulfilled. Honey, a sweet containing considerable single sugar, 

 is thus apt to cause glycosuria if too freely eaten. The greatest 

 amount that can be eaten without causing glycosuria marks the 

 assimilation limit. The other carbohydrates, since they require 

 digestion before they are absorbed, are less apt to give rise to too 

 rapid absorption. It is found, however, that there is a great dif- 

 ference in the amounts that can be taken without exceeding the 

 assimilation limit. The inversion of milk-sugar gives rise to a 

 special single sugar, galactose, which is converted into glycogen 

 very slowly. The assimilation limit for milk-sugar is correspond- 

 ingly low. Starch is digested so slowly that the assimilation limit 

 for it is quite difficult to exceed. Glycosuria resulting, not from 

 disease, but merely from overconsumption of carbohydrates, is 

 called alimentary glycosuria. 



Other Types of Glycosuria. An analysis of the carbohydrate- 

 storage mechanism just described reveals three points where an 

 upset of the normal sequence might give rise to glycosuria; and 

 three corresponding varieties are known. The three conditions 

 which may cause glycosuria are: (1) A disturbance of the mech- 

 anism which controls the rate of conversion of liver-glycogen 

 into sugar, so that more is poured into the blood than the tissues 

 are able to use; (2) a diminution in the consumption of sugar by 

 the tissues, so that more accumulates than the liver can store; 

 (3) an alteration of the kidney such that it excretes all the sugar 

 that comes to it, and thus drains sugar from the blood continuously. 

 Much insight into the working of the carbohydrate-storing mech- 

 anism, as well as the use of carbohydrates by the Body, has 

 been gained by study of these three forms of glycosuria. 



Glycosuria from Disturbance of the Liver Function. Emotional 

 Glycosuria. It has been shown that injury to a definite point in 

 the medulla destroys the co-ordination between the output of 

 sugar from the liver and the use of sugar by the tissues, with 



