CH. XII.] GLUCOSE. 309 



glucose is tolerated better on an empty stomach than when 

 taken with an ordinary meal. In general, it might be 

 stated that a normal individual should be able to absorb 

 50 grams, of glucose on an empty stomach without showing 

 any increase in the amount of sugar excreted in a given 

 time. An important result of these researches is that the 

 concentration of sugar in the urine is of much less signifi- 

 cance than the amount passed per hour. Since urine 

 always contains glucose, they suggest that the term 

 "glycuresis" should replace "glycosuria," to indicate 

 conditions characterised by an increased excretion of 



glucose in the urine. 



There are two types of glycuresis, alimentary and 

 persistent. Alimentary glycuresis is the condition in 

 which the amount of sugar absorbed exceeds the amount 

 that the individual is capable of assimilating. The limit 

 varies with the individual, and is affected by a variety of 

 pathological conditions. Persistent glycuresis is the condi- 

 tion when large amounts of sugar are excreted for a con- 

 siderable length of time, and may be quite independent 

 of the administration of carbohydrate food. The condition 

 is known as diabetes mellitus. The urine is generally 

 much increased in amount, of a high specific gravity, and 

 pale in colour. 



The classical test for sugar in urine is Fehling's (Ex. 97). It is not a 

 reliable test. Not only is Fehling's solution reduced by certain constituents of 

 normal urine, such as urates and creatinine ; but also certain of these bodies, 

 notably creatinine, form soluble compounds with cuprous oxide, and thus 

 markedly interfere with the delicacy of the test. Also the urea of the urine is 

 decomposed to ammonia, which dissolves cuprous oxide (see p. 106, note 5). 

 Further, glucose is destroyed by boiling caustic soda, so that the presence of a 

 small amount of sugar may escape detection. 



Benedict's test (Ex. 100) is a great improvement. Owing to the substitu- 

 tion of sodium carbonate for sodium hydroxide the solution is not reduced by 

 urates or creatinine. It does not give a positive reaction with the concentra^ 

 tion of glucose normally present in urine, but is very sensitive for small in- 

 creases beyond this. The author considers it the most reliable for general use ; 

 but owing to the fact that it is much more delicate than Fehling's, the result 

 of a faintly positive test is not necessarily an alarming indication of abnor- 

 mality. 



Cole's test (Ex. 381) is more sensitive than Benedict's, and the manipula- 

 tion has been so arranged as to ensure that it does not give a positive result 

 with normal urines. It is of considerable value in detecting small variations 



