THE METABOLISM OF THE CARBOHYDRATES 653 



important of these concerns the activities of the gastrointestinal appa- 

 ratus at the time the sugar is given, for it has been found that if other 

 foodstuffs are being absorbed at the same time as the sugar, more of 

 the latter can be tolerated than when the sugar alone is. being absorbed. 

 It has therefore been customary to give the sugar dissolved in water, 

 or in weak coffee, the first thing in the morning after the patient awakes ; 

 i. e., at least twelve to sixteen hours after the last meal was taken. In 

 making these tests the urine voided before the sugar is estimated should 

 of course itself be thoroughly examined for reducing substances, and 

 the urine should be collected every ninety minutes and examined by a 

 reliable test (Benedict's or Nylander's).* 



Although a limit is set to the ability of the organism for retaining 

 sugar (mono- or di-saccharides), this does not seem to apply, in healthy 

 individuals at least, when starches (polysaccharides) are ingested. Thus, 

 it is a well-known fact that people can eat enormous quantities ,of pota- 

 toes or of bread without the appearance of any trace of reducing sub- 

 stances in the twenty-four-hour urine. On the other hand, urine collected 

 and examined at short intervals (every half hour) after taking large 

 quantities of polysaccharide-rich food will frequently be found to contain 

 traces of reducing substances. 



For practical purposes it has been considered that an individual who 

 develops glycosuria after; taking 100 gm. of glucose must be considered 

 as at least a potential diabetic. In the light of the above results and 

 for many other reasons, there is, however, considerable doubt as to the 

 value of the assimilation test. Thus, when a solution of glucose is 

 given orally, its rate of absorption will depend very largely on the 

 motility of the stomach. If this is normal, the solution will very quickly 

 find its way past the pyloric sphincter into the intestine, where it will 

 be rapidly absorbed. If, on the other hand, the pyloric sphincter does 

 not open freely, the passage of the glucose into the intestine may be 

 so delayed that no more is present in this place at one time than would 

 be the case after an ordinary diet of polysaccharide. And even after 

 the sugar solution enters the small intestine, differences in the amount 

 of the intestinal contents with which it becomes mixed, in the extent of 

 bacterial growth, and in the absorption process, may very materially 

 affect the rate at which the glucose gains entry to the blood. 



Although often of doubtful diagnostic value, determination of the 

 assimilation limit is of considerable aid in controlling the treatment of 



Examination of normal individuals has shown that the assimilation limit for different sugars 

 varies somewhat; for glucose it appears to be from about 150 to 250 gm. ; for levulose, which, it 

 will be remembered, is the rnonosaccharide associated with glucose in the construction of the cane- 

 sugar molecule, the assimilation limit is from 100 to 150 gm. ; for cane sugar or saccharose itself 

 the figures seem to vary considerably, but are given as between 50 and 200 gm. ; for lactose, another 

 disaccharide, and the sugar present in milk, the assimilation limit is distinctly lower namely, 100 gm. 



