660 



DIABETES 



can take place in three different ways, to regenerate d-levulose, d-mannose and 

 d-glucose. Thus if in the case of (a), OH is added to carbon atom number one 

 OH 



this will form the group H — C — OH which represents a hydrated aldehyde group 



and will lose water to become CHO. Then H going to the second C atom com- 

 pletes the formula of d-mannose. In a similar way (b) can form d-glucose. 

 But if the OH went to the second carbon atom this group would thereby become 



a hydrated ketone similar to the hydrate of acetone and lose water to form C = O, 



while H going to the end carbon atom would complete the formula of d-levulose. 

 In a manner entirely analogous there is an enol molecule which is common to d- 

 allose, d-lactose and d-pseudo fructose (see (d) above). 



It will be noticed that each of these enols is in equilibrium with a 2-keto- 

 hexose and two aldo-hexoses. Now these 2-keto-hexoses, d-fructose and d-pseudo 

 fructose, in accordance with general ketone behavior, are capable of yielding .an- 

 other common enol, i. e., a 2-3 enol (with the double bond between the second and 

 third carbon atoms) as represented at (e) and this 2-3 enol (by a process like 

 that just detailed for the 1-2 enols) can account for the formation of the two 

 3-keto-hexoses whose formulae are given above. The same general principles hold 

 for each of the series of hexoses (For further elaboration of the theory see Xef's 

 original papers.) A similar use of enol molecules in this connection is made by 

 Neuberg. 



It remains now to point out that if to a simple aqueous solution of sugar, 

 oxygen be supplied in the form of air or H2O2, no oxidation occurs. But if the 

 solution be alkalinized then the sugar is readily burned. In the absence of oxygen 

 and the presence of alkali somewhat stronger than that found most favorable 

 for the reciprocal transformation above detailed, there occur certain irreversible 

 reactions such as the formation of lactic acid and the so-called saccharines. When 

 an alkaline sugar solution is treated with oxygen it yields CO2, HoO, and formic, 

 glycoUic, glyceric and certain trihydroxy-butyric and hexonic acids, depending 

 on the sugar used. Without oxygen, or with too little oxygen, lactic acid and the 

 saccharinic acids make their appearance (cf. the formation of lactic acid). The 

 explanation of these phenomena rests in the conception thai alkali increases the 

 dissociation of sugar, and that the dissociated fragments burn or rearrange depend- 

 ing upon the conditions of the experiment. 



i- In this connection, according to Nef, we are dealing with the alcohol groups 

 of the sugars and may advantageously turn for a moment to the properties of 

 methyl alcohol. This substance consists under ordinary circumstances of a great 



-H 



H 



H 



preponderance of undissociated molecules in d3'namic equilibrium, with a very 

 minute quantity of dissociated methylene CHsOH?:^ CH2 -|- H2O. The primary 



