686 METABOLISM 



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 administered should 

 of course itself be thoroughly examined for reducing substances, and 

 specimens should be collected about 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 is usually considered not 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 po- 

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

 stances in the twenty-four-hour urine. It should be pointed out, however, 

 that urine collected and examined at short intervals (every half hour) 

 after taking large quantities of polysaccharide-rich food has frequently 

 been found to contain traces of reducing substances in apparently 

 healthy persons. 



For practical purposes it has been considered that an individual who developes glycos- 

 uria 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, con- 

 siderable 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 

 diabetes. For this purpose the patient should first of all be instructed 

 to follow his usual diet, so that, by examination of the amount of sugar 

 excreted in the urine, an opinion may be formed of the severity of the 

 case. The diet should then be changed so as to consist of a part that 

 contains no carbohydrates and another composed entirely of starchy 



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 leyulose, which, it 

 will be remembered, is the monosaccharide 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. 



