904 PHYSIOLOGY 



sugar appears in quantities large enough to give a reaction with 

 Fehling's solution or with the phenylhydrazine test. Such a condition 

 may easily be brought about by the injection of sugar subcutaneously or 

 intravenously. It is then found that any trace of the disaecharides, 

 cane sugar or lactose, introduced in the circulation, is excreted in the 

 urine. A rather larger quantity of maltose may be injected slowly 

 without appearing in the urine, since the blood-serum contains a 

 ferment maltase, which converts the maltose into glucose. Glucose, 

 fructose, mannose, or galactose, if introduced slowly into the circula- 

 tion, are stored up as glycogen in the liver. If, however, the per- 

 centage of sugar in the blood rises above 2 parts per 1000, the sugar 

 (generally glucose) appears in the urine. When this condition of 

 hyperglyceemia (excess of sugar in the blood) is set up, the constitution 

 of the sugar in the urine no longer corresponds to that in the blood. 

 If the blood contains, e.g. 4 parts per 1000, the urine may contain from 

 2 to 7 per cent, of sugar. Up to a certain point, then, blood-sugar is 

 kept back by the kidneys as a necessary food material for the tissues. 

 Any ^excess above the normal apparently acts as a foreign substance 

 and is excreted by the kidneys in a concentration much greater than 

 that in which it exists in the blood-serum. 



(1) ALIMENTARY GLYCOSURIA. A state of hyperglycamiia 

 may be induced by the administration of abnormally large quantities 

 of glucose by the alimentary canal. The amount has to exceed 

 in a healthy individual 100 grm. in order that it shall appear in the 

 urine. In certain individuals the power of assimilating glucose 

 may be deficient so that an alimentary glycosuria may be caused by 

 any over-indulgence in carbohydrate food. In the healthy person it 

 is hardly possible to produce glycosuria by the administration of 

 starchy foods, since the liver can store up the excess of glucose as fast 

 as it is produced from the starch by digestion and absorbed into the 

 blood-serum. 



(2) DIABETIC PUNCTURE. It was shown by Claude Bernard 



that puncture of the floor of the fourth ventricle in rabbits was often 



followed immediately by an excessive secretion of urine and the 



appearance of sugar in this fluid. The glycosuria may last from 



twenty-four to thirty hours. If at the end of this time the animal 



be killed, the liver is found to be free from glycogen. A sample of 



blood taken during the height of glycosuria may contain from 3 to 



4 parts of sugar per 1000. In order that the experiment may succeed 



it is important that the animal be previously well fed. If the puncture 



or ' piqiire ' be carried out on an animal that has been starved or 



whose liver has been freed by any means from glycogen, no glycosuria 



is produced. It is evident that the effect of the puncture has been to 



cause a rapid conversion of the glycogen previously stored up in the 



