Carbon Assimilation. 
§3 
The subject is clearly one which interested van’t Hoff deeply, 
as is seen from his letters and diary (Cohen, 1912), and he intended 
to subject the problems to an extensive investigation. Bad health, 
and finally death, prevented him from carrying out this project, 
and we only possess from his hands two papers on the subject 
(1909, 1910) entitled “ On Synthetic Enzyme Action,” neither of 
which is of interest here. 
Van’t Hoff’s suggestion obtains a new interest in view of 
Willstatter’s discovery that chlorophyll is a double ester of two 
primary alcohols, and that leaves contain an enzyme which can 
effect hydrolysis or alcoholysis of chlorophyll, and can also 
synthesize chlorophyll from phytol and chlorophyllid (Willstatter 
and Stoll, 1911, 1913). Unfortunately, as we have pointed out 
earlier, Willstatter’s contention that the amount of pigment is not 
altered during assimilation, only holds for the chromogen complex, 
and provides no information as regards the alcohol groups. 
Therefore we have no indication whether chlorophyllase or the 
alcohol groups play any part in the processes of carbon assimi¬ 
lation. 
D. Suggestion of Siegfried. 
Siegfried (1905) worked on the action of carbon dioxide on 
amino-acids and proteins, and came to the conclusion that definite 
compounds, carbaminic acids and carbaminates are produced. 
Thus he says that his results “appear to justify the assumption 
that where carbon dioxide meets protein in the animal organism, 
carbon dioxide is fixed organically, and that the compounds so pro¬ 
duced dissociate again with evolution of carbon dioxide.” After 
discussing the bearing of this conclusion on various processes in 
animal physiology, such as blood processes, and the working of 
muscle, he concludes: “Finally, plant physiology also will have 
to concern itself with this question. Where there is chlorophyll 
there is also protoplasm. If by the intake of carbon dioxide by 
the plant carbamino groups are formed, the intake of carbon 
dioxide will be accelerated. Instead of, or along with the question, 
how is carbon dioxide reduced, the question must be solved, how 
are carbon acids reduced.” 
It will be seen that we have here a suggestion in regard to the 
processes of carbon assimilation which differs markedly from 
the Baeyer hypothesis. It is generally assumed that in the first 
stage of the assimilatory process the carbon dioxide takes part in 
