114 DYNAMICS OF LIVING MATTER 



It is perhaps of special biological significance that the oxidation 

 of many dysoxidizable substances occurs more rapidly in the light than 

 in the dark. Schonbein and recently Jorissen have shown that alde- 

 hydes are oxidized more rapidly in the light than in the dark; the 

 same is true for oil of turpentine. According to Richardson and For- 

 teg, amylalcohol is oxidized quicker in light than in the dark. Bod- 

 lander is inclined to attribute these effects of light to a dissociation of 

 oxygen; his assumption is based upon the electromagnetic theory 

 of light.* 



It is a common biological conception that the occurrence of pigment 

 in animals or plants bears a close relation to biological effects of light ; 

 we may perhaps for this reason quote an observation which bears on 

 this problem. The observation was made by H. W. Vogel.f The 

 silver salts and especially the bromide of silver of common negatives 

 are preeminently sensitive for rays between blue and ultraviolet. If, 

 however, eosin or cyanin is added in traces, the maximum of the photo- 

 graphic effect moves toward the side of the longer waves in the spec- 

 trum. 



After this preliminary orientation we shall discuss briefly the bio- 

 logical effects of light. The most important biological role of light 

 lies in the assimilatory activity of green plants. The transformation 

 of the CO 2 of the air into sugar (and starch) in the green plant occurs 

 only under the influence of light. This assimilation occurs in chloro- 

 phyll granules (or on their surface) inside the cells of green plants (or 

 certain animals). All attempts thus far made to separate a substance 

 from the chlorophyll which is able to form sugar from the CO 2 of the 

 air have f ailed. | Narcotics like ether and chloroform which inhibit 

 the motor activities of the cell also inhibit the chlorophyll action. (This 

 indicates also that the narcotics have another action than a mere physi- 

 cal one, as Overton assumes.) Yet it is not unlikely that in respect to 

 chlorophyll, a similar experience will be made to the one made in regard 

 to zymase; namely, that mere technical difficulties at present prevent 

 the isolation of the assimilating catalyzer in the chlorophyll granules 

 from the living cell. 



The chemical side of the process of assimilation is unknown. Baeyer 

 suggested that from H 2 CO 3 at first formaldehyde, HCOH, is formed 

 which by polymerization yields C 6 H J2 O 6 . Hoppe-Seyler expressed 

 the idea that chlorophyll undergoes first a combination with H 2 CO 3 



* Bodlander, Ueber langsame Verbrennung. (Ahrens' Sammlung chemischcr und 

 chemisch-technischer I'ortrage}, Stuttgart, 1899. 



t I quote after Ostwald's Grundriss der allgem, Chemie. 



j R. O. Herzog, Hoppe- Stylets Zeitsch. fiir physiol. Chemie, Vol. 35, p. 459, 1902. 



Hoppe-Seyler, Physiologische Chemie, 1876. 



