EXPERIMENTAL DIABETES 383 



It may be, as Langstein ( 2 ) has pointed out, that the cause of 

 the discordant results obtained by different workers is that the 

 same form of leucin has not been used. Felix Ehrlich has 

 recently shown that leucin, as prepared by the usual methods, is 

 not only a mixture of several isomeric forms of this body, but 

 that there are also frequently mixed with it amido-acids con- 

 taining fewer carbon atoms than six. In any case, this is a 

 portion of our subject urgently requiring further investigation. 



The invariable presence of oxy-amino acids amongst the 

 decomposition products of proteids furnishes us with a further 

 illustration of how sugar may be formed from this source. For 

 example, serin, the oxy derivative of alanin, has been found by 

 Emil Fischer ( 2 ) and his co-workers to be a very common decom- 

 position product of proteid. Serin is oxy-amido-propionic acid, 

 CH 2 OH . CH NH 2 . COOH ; by substitution of the OH group by 

 hydrogen, alanin is formed, which, as we have seen, easily passes 

 into dextrose. Furthermore, the Zto-derivative of serin is cystein, 

 having the formula CH 2 SH . CH NH 2 .COOH (protein cystein) or 

 CH 2 NH 2 .CHSH COOH (stein cystein). Cystein occurs plentifully 

 in the body and is closely related to the taurin of bile. 



The possible relationship of this to dextrose is best seen by a 

 comparison of the following formulae (after Neuberg) : 



CH 2 SH . CH(NH) 2 COOH (Proteincystein) 

 CH 9 NH 2 - CHSH . COOH (Steincystein) 

 CH 2 OH - CHNH 9 - COOH (Serin) 



|~CH 3 - CH(NH) 2 - COOH (Alanin) ~| 



[_CH 3 - CH(OH) - COOH (Lactic acid)J 

 CH 2 OH - CHOH - COOH (Glyceric acid) 

 CH,OH - CHOH - CHO (Glyceric aldehyde) 

 CH 2 OH - (CHOH) 4 - CHO (Dextrose) 



Of the other decomposition products of proteid there is not as 

 yet a great amount of evidence that they may form dextrose. 

 Neuberg, however, has shown that certain diamido-acids can be 

 converted into oxy-amido-acids, which, as we have seen, may 

 easily be transformed into dextrose. 



Before concluding it should be mentioned that Seegen and 

 others ( 39 ) have stated that in the post-mortem production of 

 dextrose by the liver a greater increase of sugar occurs than 



