THE ORIGIN OF LIFE 147 



merly thought to be the case. In animals, as is well known, 

 glycogen or animal starch is formed not by direct synthesis, 

 but by deamination and reduction of proteins. In a similar 

 way, it is thought that the production of carbohydrates in 

 plants may be due to a breaking down of the phytyl ester 

 in chlorophyll, the chromogen group functioning (under the 

 action of light) alternately as a dissociating enzyme in the 

 formation of sugars and a synthesizing enzyme in the recon- 

 struction of chlorophyll. Phytol is an unsaturated alcohol 

 obtained when chlorophyll is saponified by means of caustic 

 alkalis. Its formula is C20H39OH, and chlorophyll consists of 

 a chromogen group containing magnesium (MgN4C32H3oO) 

 united to a diester of phytyl and methyl alcohols. 



Experimental results are at variance with the theory that 

 chlorophyll acts as a sensitizer in bringing about a reduction 

 of carbonic acid, after the analogy of eosin, which in the 

 presence of light accelerates the decomposition of silver salts 

 on photographic plates. Willstatter found that, when a col- 

 loidal solution of the pure extract of chlorophyll in water is 

 exposed to sunlight and an atmosphere consisting of carbon 

 dioxide exclusively, no formaldehyde is formed, but the 

 chlorophyll is changed into yellow phseophytin owing to the 

 removal of the magnesium from the chromogen group by the 

 action of the carbonic acid. Jorgensen, on the other hand, 

 discovered that in an atmosphere of pure oxygen, formal- 

 dehyde is formed, apparently by the splitting off and re- 

 duction of the phytyl ester of chlorophyll. Soon, however, 

 the formaldehyde is oxidized to formic acid, which replaces 

 the chlorophyllic magnesium with hydrogen, thus causing 

 the green chlorophyll to degenerate into yellow phseophytin 

 and finally to lose its color altogether. The dissociation of 

 the chromogen group may be due to the fact that the reaction 

 takes place in vitro, and may not occur in the living plant. 

 At all events, it would seem that plants, like animals, manu- 

 facture carbohydrates by a destructive rather than a con- 

 structive process, and that water and carbon dioxide serve 



