45 o A MANUAL OF PHYSIOLOGY 



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

 temporary glycosuria, but something seems to depend 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 ash- and 

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

 tasked even his Japanese powers of digestion to dispose of, found not 

 a trace of sugar in the urine. Glucose, 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. 527).* 



But, except as an occasional phenomenon, such an ex- 

 cretion 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 con- 

 stituent 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 proportion 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. 



It has been asserted that the blood which leaves even 

 a resting muscle, or an inactive salivary gland, is poorer in 

 sugar than that coming to it ; and the conclusion has been 

 drawn that in the metabolism of resting muscle and gland 

 sugar is oxidized, the carbon passing off as carbon dioxide 

 in the venous blood. This is indeed extremely likely, for 

 we know that when the skeletal muscles of a rabbit or 

 guinea-pig are cut off from the central nervous system by 



* 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 

 phenylhydrazine 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*918 grammes by 

 Fehling's method and 8*288 grammes by the polarimeter) ; the highest 

 proportion of the quantity taken which appeared in the urine was 2*5 per 

 cent. When glucose was found, cane-sugar was always present as well. 



