516 A MANUAL OF PHYSIOLOGY 



is attested by such a cloud of modern witnesses that it seems 

 to be firmly and finally established. 



Fate of the Sugar Glycolysis. What, now, is the fate of 

 the sugar which either passes right through the portal circula- 

 tion from the intestine without undergoing any change in the 

 liver, or is gradually produced from the hepatic glycogen ? 

 When the proportion of sugar in the blood rises above a certain 

 low limit (about 1-5 or 2 to 3 parts per 1,000), some of it is 

 excreted by the kidneys (Practical Exercises, p. 609). 



A large meal of carbo-hydrates is frequently followed by a 

 temporary glycosuria, but much depends upon the form in 

 which the sugar-forming material is taken. Miura, for example, 

 after an enormous meal of rice (equivalent to 6*4 grammes of 

 ash- and water-free starch per kilo of body- weight) , which, as he 

 mentions, tasked even his Japanese powers of digestion for such 

 food to dispose of, found not a trace of sugar in the urine. 

 Dextrose, cane-sugar and lactose, on the other hand, when taken 

 in large amount, were in part excreted by the kidneys, as was also 

 the case with levulose and maltose in a dog (Practical Exercises, 

 p. 610).* It has been suggested as an important practical rule 

 that a person who can tolerate a certain amount of dextrose (say 

 2 grammes per kilo of body-weight taken not less than two hours 

 after a meal) without excreting a portion of it is not the subject of 

 incipient diabetes. Many healthy persons can tolerate much more. 



Except as an occasional phenomenon, glycosuria other than 

 alimentary is inconsistent with health ; and therefore in the 

 normal body the sugar of the blood must be either destroyed or 

 transformed into some more or less permanent constituent of the 

 tissues. The transformation of sugar into fat we have already 

 mentioned, and shall have again to discuss ; it only takes place 

 under certain conditions of diet, and no more than a small pro- 

 portion of the sugar which disappears from the body in twenty- 

 four hours can ever, in the most favourable circumstances, be 

 converted into fat. Accordingly, it is the destruction of sugar 

 which concerns us here, and there is every reason to believe that 

 this takes place, not in any particular organ, but in all active 

 tissues, especially in the muscles, and to a less extent in glands. 



* Twenty-four healthy students, whose urine had previously been 

 shown to be free from sugar, ate quantities of cane-sugar varying from 

 250 grammes to 750 grammes. The urine was collected in separate 

 portions for twelve to twenty-four hours after the meal. In only three 

 cases was reducing sugar found in the urine (by Fehling's and the phenyl- 

 hydrazine test), and then merely in traces. In eight cases cane-sugar 

 was found, and estimated by the polarimeter, and, after boiling with 

 hydrochloric acid, by Fehling's solution. The greatest quantity of cane- 

 sugar recovered from the urine was 8 grammes (7*92 grammes by Fehling's 

 method and 8*29 grammes by the polarimeter) ; the highest proportion 

 of the quantity taken which appeared in the urine was 2' 5 per cent. When 

 dextrose was found, cane-sugar was always present as well. 



