EXPERIMENTAL DIABETES 367 



to a diabetic patient on an otherwise constant diet, and seeing 

 how much of it can be recovered from the urine (vide Pancreatic 

 Diabetes, p. 351). It has usually been found that a large propor- 

 tion of the administered dextrose can be recovered in this way, 

 though not usually all of it. Von Noorden ( 29 ), however, records 

 a case in which all the administered dextrose reappeared. 



With regard to other sugars than dextrose, it has been noted 

 that Icevulose is much more readily utilised by the diabetic than 

 dextrose is, especially in the milder forms of the disease, where 

 it usually causes no increase in the glycosuria ; in the severer 

 forms of diabetes it may but cause a slight rise in the excretion 

 of dextrose, while in other cases not only is dextrose increased, 

 but laevulose itself may appear in the urine. We have already 

 seen that in pancreatic diabetes in the dog, laevulose is the only 

 sugar which leads to glycogen formation. There can, therefore, be 

 no doubt of the power of the diabetic organism of choosing 

 between the two sugars ; and it is interesting to note that this 

 power is not confined to the animal body, but is exhibited by low 

 forms of life : e.g. a pure culture of the yeast plant (Saccharomyces 

 apiculatus) can ferment dextrose and Isevulose, but is inactive on 

 solutions of other sugars. 1 If cane-sugar be given to a diabetic 

 the increase in the dextrose excretion in the urine will amount to 

 about one-half of the administered cane-sugar, the dextrose portion 

 of the cane-sugar is excreted but the leevulose portion is destroyed. 

 This interesting fact recalls one of Pasteur's first discoveries : that 

 Penicillium glaucum, a common fungus, when grown in a solution 

 of inactive racemic acid, which consists of a double molecule of right 

 and left rotating racemic acid, destroys the left-rotating molecule, 

 but has no action on the right-rotating molecule. 



The behaviour of other disaccharides and of polysaccharides 

 will be readily understood if the above facts be borne in mind. 



Further proof that the human organism in D. mellitus has 

 largely lost the power of utilising dextrose if indeed further proof 

 be needed is furnished by an examination of the respiratory 

 quotient. This, it will be remembered, is a fraction representing 

 the relative amounts of carbon dioxide (C0 2 ) expired and of 



CO 

 oxygen (0 2 ) retained in the body. It is written -^. 2 - When 



1 Dextrose and laevulose have distinctly different chemical structures, so 

 that the discrimination of them by the tissues is quite conceivable. 



