Not yet prepared. 



The detailed discussion here of these purely chemical problems is com- 

 pletely justified on account of the great significance which these investiga- 

 tions have for biology, and as a matter of fact it will not be possible to 

 understand clearly the metabolism of carbohydrates without having a 

 thorough knowledge of such structure questions as we have briefly touched 

 upon. 1 



The ways and means by which sugars rich in carbon are prepared syn- 

 thetically from those with fewer carbon atoms are not without interest 

 for biology. All the compounds represented on the preceding page con- 

 tain an aldehyde group, and aldehydes are capable of combining with 

 hydrocyanic (prussic) acid. By saponifying the cyanhydrins and sub- 

 sequent reduction, a new sugar is obtained, as E. Fisher and later Kiliani 2 

 showed, which contains more carbon than the original sugar. In this way, 

 it is possible to prepare not only hexoses from the simplest members of 

 the carbohydrate group, but sugars with seven, eight, and nine atoms of 



1 Since we shall meet with the same point of view in the case of other classes of 

 substances, especially the proteins, the student is advised to refer to some of the books 

 on the subject. 



3 Her. 18, 3066 (1885); 19, 221, 767, and 1128 (1886). 



