METABOLISM 41 



consequent imperfect assimilation of carbohydrates 

 various diseased states may arise. Some cases of 

 glycosuria in elderly subjects, for example, may be due 

 to sugar running off through the kidneys instead of 

 going to form fat. Such persons are only ' glycosurics ' 

 because they are not obese. 



That sugar can be formed in the body from sources 

 other than glycogen a study of the chemical phenomena 

 of diabetes has made quite clear, and it was at first 

 supposed that proteins were the source from which sugar 

 could be so derived. This view received confirmation 

 when it became known that most proteins contain a 

 carbohydrate moiety usually glucosamin in their 

 molecule. Subsequent investigation, however, has sug- 

 gested doubts as to whether proteins can be an important 

 source of sugar, and whether their glucosidal constitution 

 is an adequate explanation of it for, in the first place, 

 the commonest and most usual proteins are those which 

 contain least of the carbohydrate element; and in the 

 second place, diabetics may continue to produce large 

 quantities of sugar even when fed on proteins, such as 

 casein, which contain no carbohydrate radicle at all. It 

 has therefore recently been suggested that the amido- 

 acid alanin and possibly also glycocoll and leucin 

 may be the source of the carbohydrate derived from 

 protein. At all events, there can be no question that 

 sugar can be formed in the body from proteins, and that 

 in severe cases of diabetes it may be as necessary to 

 limit the consumption of protein as it is to restrict that 

 of carbohydrates themselves. 



Opinion has now veered round towards regarding even 



