THE CHEMISTRY OF THE ANIMAL BODY. 1005 



c?-mannonic acid is divided and one part treated with hydrogen, with resulting 

 d-mannose, which, as has been shown above, is convertible into eZ-fructose 

 or ordinary fruit-sugar ; the second part of the cZ-mannonic acid treated with 

 chinolin is transformed through change in configuration into its isomer, 

 d-gluconic acid, which on reduction yields c?-glucose, or ordinary dextrose. 

 This shows the preparation of the common sugars from their elements. The 

 transformation of levulose into dextrose is especially to be noted, since it takes 

 place in the body. 



H H OHH 



d-Glucose, Dextrose, Grape-sugar, CH 2 OH C C C C CHO. 



OH OHH OH 



This is the sugar of the body. It is found in the blood and other fluids and in 

 the tissues to the extent of 0.1 per cent, and more, even during starvation. The 

 principal source of the dextrose of the blood is that derived from the digestion 

 of starch, and also of cane-sugar, in the intestinal tract. Dextrose is likewise pro- 

 duced from proteid, for a diabetic patient fed solely on proteid may still excrete 

 sugar in the urine. Minkowski l finds that in starving dogs after extirpation 

 of the pancreas the proportion of sugar to nitrogen is 2.8 : 1. The same ratia 

 has been shown to exist in phlorizin diabetes in rabbits 2 when the drug is 

 administered in a certain way. 



In calculating this production of glucose from proteid, it is discovered to be 

 a process of oxidation, in which 45 grams of dextrose are formed from every 

 100 grams of proteid decomposed. 3 The sugar so formed contains 44 per cent, 

 of the physiologically available energy of the proteid consumed. The pancreas 

 may perhaps manufacture a ferment which, supplied to the tissues, becomes the 

 first cause of the decomposition of dextrose, and in whose absence diabetes 

 ensues. Excess of dextrose in the body is stored up, especially in the liver- 

 cells, as glycogen, which is the anhydride of dextrose ; the glycogen may be 

 afterwards reconverted into dextrose. The presence of sugar in the body in 

 starvation, even when little urea may be detected there, shows the readier excre- 

 tion of the nitrogenous radical of proteid. Traces of dextrose are found in 

 normal urine. 



Dextrose is a sweet-tasting crystalline substance ; its solutions rotate polar- 

 ized light to the right. 



H H OH 



d-Fructose, Levulose, Fruit-sugar, CH 2 OH C C C COCH 2 OH. 



OH OHH 



This occurs in many fruits and in honey. It is sweeter than dextrose, and 

 rotates polarized light to the left. It is a product of the decomposition of 

 cane-sugar in the intestinal canal. If levulose be fed, any excess in the blood 

 may be converted into glycogen, and through the. glycogen into dextrose. It 

 is possible thus to convert 50 per cent, of the levulose fed into dextrose. 4 



1 Archiv fur Physiologic und Pharmakologie, 1893, Bd. 31, p. 85. 



2 Lusk: Paper read before the American Society of Physiology, Philadelphia, 1895. 



3 Weintraud and Lanes: Zeitschrift fur physiologische Chemie, 1894, Bd. 19, p. 632. 

 * Minkowski : Archiv fur Pathologie und Pharmakologie, 1893, Bd. 31, p. 157. 



