CHAPTER LXXVI 

 THE METABOLISM OF THE CARBOHYDRATES 



The healthy animal organism is capable of rapidly oxidizing large 

 quantities of carbohydrate, as is evident from the following facts: If 

 carbohydrate is given to a starving animal, (1) the energy output very 

 shortly afterward increases; (2) the respiratory quotient also increases, 

 indicating that, relatively to oxygen intake, more carbon dioxide is being 

 excreted (see page 582) ; and (3) none of the ingested carbohydrate 

 makes its appearance in the excreta. Indeed, of the three proximate 

 principles of food, carbohydrate is the most available for combustion 

 in the animal body. It may therefore be considered as the quickly 

 available fuel for the body furnaces. 



CAPACITY OF THE BODY TO ASSIMILATE CARBOHYDRATES 



Assimilation Limits. When the limit to the amount of carbohydrate 

 that the organism can metabolize is overstepped, some of it appears in 

 the urine. The amount that can be tolerated without causing glycosuria 

 is commonly called the assimilation or saturation limit. The use of the 

 term " limit" is, however, very unfortunate, for it implies that beyond 

 this point the organism is capable of dealing with no more carbohy- 

 drate, which is far from being the case, for if a larger amount is taken, 

 only a small trace of the excess will appear in the urine. When the 

 urine is allowed to collect for twenty-four hours, the mixed specimen 

 shows no trace of glucose in the majority of healthy individuals after 

 the ingestion of 200 gm. ; after 300 gm. a somewhat higher percentage 

 of cases develop a mild glycosuria, but frequently none is evident even 

 after 500 gm. Beyond the last mentioned amounts the limit of ingestion 

 is reached, on account of nausea, etc., and it is improbable even if 

 larger amounts could be tolerated, that any more of the glucose would 

 be absorbed than with 300 or 400 gm. The testing of the so-called as- 

 similation limit has been considered an important aid in the diagnosis 

 of early cases of diabetes. 



It has been found that to make the results of any value, certain 

 conditions must be fulfilled in applying the assimilation test. The most 

 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 



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