58 LECTURE IV. 



fact, O. Ruff has shown. 1 He prepared d-gluconic acid by the oxida- 

 tion of d-glucose; its calcium salt he allowed to stand in the sunlight in 

 the presence of ferric acetate, or he treated it with hydrogen peroxide 

 and thus obtained d-arabinose. 



CHO CO.OH CHO 



HCOH HCOH HOCH 



HOCH HOCH HCOH 



HCOH HCOH HCOH 



HCO] 



>H HCOH 



CH 2 OH CH 2 OH CH 2 OH 



d-glucose d-gluconic acid d-arabinose 



At all events, and this is of great importance, we can explain 

 chemically without difficulty the formation of the different members of 

 the carbohydrate series from the hexoses, especially d-glucose. 



Emil Fischer 2 has suggested that the glycerose discovered by him is 

 perhaps the first assimilation product of carbonic acid by the plant cells 

 containing chlorophyll. By the combination of two molecules of this, it 

 is easy to understand how hexoses may be formed. Again, glycerose may 

 be of great importance in other relations. We shall mention here merely 

 the fact that it is closely related to glycerol, which is one of the components 

 of the fats; and on the other hand, that from this point of the carbon dioxide 

 assimilation the synthesis of albumin may start. Glycerose, as we shall 

 show more fully later on, stands in close relation to certain of the decom- 

 position products of albumin, namely alanine, serine, and cystine. Naturally 

 it does not necessarily follow that either the formation of the fats or that 

 of the proteins must begin with this hypothetical product of assimilation. 

 It is indeed possible that glycerose appears merely as one of the decom- 

 position products of d-glucose or starch, and then is used for syntheses 

 by the plant cell. 



All of these possibilities have been brought forward in order to bring 

 the ground-plan of the whole carbon assimilation at least within the realms 

 of our understanding, and to show the far-reaching value that purely 

 chemical investigations, especially those of Emil Fischer, have upon the 

 science of biology; for it is by this means only that the most important 

 classes of substances carbohydrates, fats and proteins have been 

 traced back to a common source. The consideration of these relations is 



1 Ber. 31, 1573 (1898); 32, 550 (1899). Otto Ruff and Ollendorf: ibid. 33, 1798 

 (1900). Cf. A. Wohl: ibid. 26, 730 (1893) ; 33, 3666 (1899). 



2 Ber. 23, 2138 (1890). 



