664 DIABETES 



to 6.25 grams protein, and if for each 6.25 grams pi*otein metabolized as 

 indicated by the N in the urine, 3.65 grams glucose are excreted, then 

 58 per cent, of the protein metabofi/.ed is converted into glucose and 

 so excreted. In like manner the 2.8 : 1 ratio would indicate a 45 per 

 cent, conversion. A percentage above 58 has not been satisfactorily 

 proven to occur. If to the fully phlorhizinized dog a definite quan- 

 tity of glucose, galactose, starch or other assimilable form of carbo- 

 hj'drate is given, this may under favorable circumstances be excreted 

 quantitatively in the urine as glucose, and the ratio of G : N will rise. 

 The sugar which appears in the urine under such circumstances over 

 and above that represented by N X Gr : N has been called "extra 

 sugar" by Lusk. 



If all the carbon contained in protein were converted into glu- 

 cose, and all this excreted together with the nitrogen, the G : N ratio 

 would be 8.25 : 1. A higher ratio than this would necessarily mean 

 that sugar was coming from some source other than protein, or that all 

 of the N was not appearing in the urine, some being retained in the 

 bod}'. If the liver were free from glycogen and no carbohydrate 

 were eaten, such a high ratio would speak in favor of sugar forma- 

 tion from fat. Falta reports having seen cases of diabetes in which 

 this occurred, but in human cases it is difficult to be sure of the 

 absence of glycogen and food carbohydrate ; moreover, such high ratios, 

 unless too long continued, might imply retention of nitrogen. Thus, 

 in thyreopriva, a nitrogenous substance is retained in the body 

 ^myxoedema fluid) ; if this substance contains more N than the total 

 weight divided by 6.25, a portion of protein must be metabolized, 

 having a lower percentage of N. This latter portion could give a 

 higher G : N ratio than normal protein. 



Sugar from Other Substances. — A large number of other substances 

 when administered to phlorhizinized dogs are capable of increasing 

 the output of sugar. Of importance in tliis connection are certain of 

 the amino acids, viz. : glycine, alanine, aspartic and glutamic acids, 

 and arginine. Others, such as leucine, tyrosine and phenyl alanine 

 do not form sugar in the body but increase the output of the acetone 

 substances. Tlie sugar-forming power of protein is doubtless due to 

 its content of the former group of amino acids.^- Lactic acid and 

 glycerol are also among the sugar formers. 



The chief interest in phlorlii/in diabetes lies in tlie opportunities 

 it offers of studying the charac'ter of the intermediate metal)olism 

 minus that of sugar, and so of studying sugar metabolism. Another 

 interest might be found were the physiologic effects of this glucoside 

 in animals interpreted with relationsliip to its normal role in plant 

 physiology. 



42 See Dakin, Jour. Riol. Clicin., 1913 (14), 155. 



