ASSIMILATION OF CARBON' 1 3 



Results of this kind are exceedingly important in biochemistry, since they 

 seem to illuminate the most remote period in the evolutionary development of 

 organisms, and point to a common origin of the plant and animal worlds. Dar- 

 win's theory of the origin of species is based upon the conception of variability 

 in structure, influenced by environmental conditions in the struggle for existence. 

 But the differences between organisms lie, not only in the form and structure 

 of the various organs, but also in the chemical properties of the substances con- 

 stituting the living cells. The character of the metabolic processes is dependent 

 upon the nature of the intracellular substances, and these processes, in their 

 turn, determine the configuration of the cells and their differentiation into 

 organs. In other words, the form of the cell-complexes composing the different 

 organs is determined by metabolism as this has been developed by the various 

 organs in the struggle for existence, relative to various environmental condi- 

 tions. With a change of conditions, their chemical constitution and their 

 metabolism are modified, which explains why they frequently change their 

 form also. Thus, to obtain a fundamental conception of the evolution of the 

 organic world, not only the structure but also the chemical composition of the 

 cells and the products of their metabolism must be considered. From this 

 viewpoint the work of Schunck and Marchlewski, whereby the leaf and blood 

 pigments are shown to be related chemically, though widely different as to 

 function, is of great scientific interest. 1 



According to Nentskii, 2 chlorophyll and hemoglobin arise from chromogens 

 that are protein decomposition products. A substance called tryptophan is 

 formed in protein decomposition by pancreatic juice; tryptophan is colored red 

 by bromine and is related, in its percentage composition, to hematoporphyrin 

 and the melanins. 



The decomposition products of chlorophyll can be separated, according to 

 Willstatter, 3 into two groups. Those obtained by the action of acids contain 

 no magnesium; the action of alkalies, on the other hand, results in such deriva- 

 tives as glaucophyllin, rhodophyllin, pyrrophyllin, and phyllophyllin, all of which 

 contain magnesium. If acids are allowed to act upon these latter substances, 

 new compounds without magnesium arise, which are related to hematoporphyrin ; 

 in this way phylloporphyrin is obtained from phyllophyllin. The action of 

 acids upon chlorophyll itself gives phaophytin, in which the phytyl can be re- 

 placed by the ethyl group, giving ethyl phceophorbide; chlorophyllin modified by 

 the action of acid is designated as phseophorbide, and phseophytin may thus 

 be termed phytyl-phaeophorbide. 



i Nencki, M., Sur les rapports biologiques entre la matiere colorante des feuilles ct celle du sang. Arch, 

 sci. biol. St.-Petersbourg 5: 254-260. 1897. 



2 Nencki, M., Ueber die biologischen Beziehungen des Blatt- und des Blutfarbstoffes. Ber. Deutsch. 

 Chem. Ges. 2o 7// : 2877-2883. 1896. 



» Willstatter, Richard, and Pfannenstiel, Adolf, Ueber Rhodophyllin. Liebig's Ann. Chem. u. Pharm. 

 358: 205-265. 1908. Willstatter and Fritzsche, 1909. [See note 3. P- "•] Willstatter and Hocheder, 

 1907. [See note 1, p. 8.] Willstatter, Richard, and Stoll, Arthur, Spaltung und Bildung von Chlorophyll. 

 Liebig's Ann. Chem. u. Pharm. 380: 148-154- I9H. Willstatter, Richard, and Isler, Max., Vergleichende 

 Untersuchung des Chlorophylls verschiedener Pflanzen. III. Ibid. 380: 154-176. I9H- [The whole 

 series of studies is summarized by Willstatter and Stoll, 1913- (See note 6, p. 6-^ 



