STORAGE OF POTENTIAL ENERGY 435 



as a rule optically active, i. e., rotate the plane of polarized light to the* 

 right or left, the products of laboratory-syntheses and those substances 

 in nature which have never passed through the life-cycle (and some of 

 those which have done so) are optically inactive. It is true that we 

 can decompose a racemic and optically inactive mixture into optically 

 active parts by utilizing the selective enzymatic activities of Yeasts, 

 or, as Pasteur did, we may sort out large crystals by hand into two 

 kinds possessing equal and opposite rotatory powers, but it will be 

 observed that all of these processes involve the intrusion of a living 

 agent. According to the view of Byk, optical activity originated in 

 the earth through the circular polarization of light which occurs when 

 light is reflected from the surface of the sea. If, on the other hand, we 

 revert to Arrhenius' theory of the origin of life upon the earth, we may 

 suppose that optical activity was transmitted to this planet by Bacterial 

 Spores floating in interstellar space. However this may be, the 

 phenomenon of optical activity is at present a distinguishing charac- 

 teristic of the components of living matter, and it originates in the very 

 first step in the life-cycle, for the carbohydrates which result from the 

 photosynthetic activities of plants are optically asymmetrical. 



Notwithstanding the fact that the immediate connection between 

 the assimilation of carbon dioxide by green plants and the appearance 

 of carbohydrates has long been understood, the intermediate products 

 which are formed in the process; the various stages which link the 

 absorption of carbon dioxide to the appearance of starch or sugars in 

 the tissues, have long been sought for in vain. The classical theory, 

 proposed by Baeyer in 1 870, is that the carbon dioxide is first reduced 

 to Formaldehyde 



CO 2 + H 2 O -> HCHO + O 2 



and that the formaldehyde which is thus formed is subsequently con- 

 densed to a hexose: 



6HCHO = C 6 Hi 2 O 6 



If this view is correct then we should expect to find formaldehyde 

 among the constituents of the green plants when engaged in active 

 assimilation. Very many attempts have been made to establish the 

 presence of formaldehyde in the tissues of plants and they cannot yet 

 be said to have yielded any very definite information. Several excep- 

 tional difficulties attach to this investigation. In the first place it is 

 certain that if formaldehyde occurs in green leaves at all it is never 

 present except in very minute amounts. Indeed it is essential that this 

 should be so, because formaldehyde is a very powerful protoplasmic 

 poison and the accumulation of any amount in excess of a minute trace 

 would result in the complete arrest of protoplasmic activities. Thus 

 Elodea canadensis is cited as a form which is exceedingly resistant to 

 the toxic action of formaldehyde, yet it will only withstand a 0.001 

 per cent, solution. 



