Januaet 26, 1917] 



SCIENCE 



77 



to specify only those whioh play an important role 

 in plant and animal life) all of which are im- 

 portant substances to life, are asymmetric, and 

 indeed have the kind of asymmetry in which the 

 image is not superposable with the object. . . . 

 When I assert that no artificial substances with 

 molecular asymmetry are known, I speak of arti- 

 ficial substances in the proper sense of the word, 

 which are formed in all their parts from the ele- 

 ments, or are produced from bodies which are not 

 asymmetric. ... In this way the idea of the in- 

 fluence of the molecular asymmetry of natural 

 organic products is introduced into physiological 

 studies; this important characteristic is perhaps 

 the only distinct line of demarkation which we 

 can draw to-day between dead and living nature. 



This view originally advanced by Pas- 

 teur is now so firmly established that no 

 chemist would hesitate to take it into con- 

 sideration in determining the origin of 

 naturally occurring products. For ex- 

 ample, it is a well-known fact that certain 

 mineral oils found in nature are optically 

 active and "Walden, Engler and other in- 

 vestigators have contended that because of 

 this property, these oils must be regarded 

 as of organic rather than mineral origin. 



The question that concerns us, however, 

 is whether this inability to reproduce in the 

 laboratory the results which are obtained 

 in the living organism is due to a complete 

 difference between the methods of the labo- 

 ratory and those of nature, or whether it is 

 due simply to lack of knowledge as to the 

 conditions necessary for effecting the syn- 

 thesis. It is evident that Pasteur inclined 

 to the latter belief. In one of his lectures, 

 after emphasizing that only the dextro or 

 levo forms are produced in nature, he adds : 



But why right and left molecules, why not only 

 symmetrical molecules like those of the inorganic 

 substances? There are certainly causes for this 

 remarkable behavior of the molecular forces, even 

 though it is dif&oult for us to get a clear concep- 

 tion of them. I believe that I am not deceived 

 when I assert that we now know one of its most im- 

 portant characteristics. Is it not necessary and 

 also sufficient to assume that the instant the plant 

 organism arises an asymmetric force is active? 



For we have seen above that the dextro-molecule 

 deviates from its levo-antipode only in those cases 

 in which it is subjected to some kind of an asym- 

 metric action. Do such asymmetric agencies arise 

 from the cosmic influences, light, electricity, mag- 

 netism, heat? Do they perhaps stand in close re- 

 lation with the earth movements, with the eleetrio 

 current by means of which physicists explain the 

 earth's magnetic pole. 



Pasteur put his beliefs to the test by at- 

 tempting to bring about asymmetric syn- 

 theses through the agency of the magnetic 

 field as well as of polarized light. 



It is evident that nature may act in one 

 of two ways in building up active forms. 

 In the first place asymmetric forces may be 

 present of which we have no knowledge, 

 through whose influence a single active 

 form may be built up ; or both of the active 

 forms may result just as in our laboratory 

 synthesis but, through some agency un- 

 known to us, one of these forms may be 

 used up by the organism or destroyed as 

 fast as formed. The latter view is the one 

 most generally accepted. Attention was 

 called to the plausibility of this view by 

 Fischer in a lecture delivered before the 

 German Chemical Society in 1890. In this 

 lecture after calling attention to the fact 

 that only the active sugars of the dextro- 

 mannite series are found in plants, Fischer 

 adds : 



Are these the only products of assimilation? Is 

 the preparation of optically active substances a 

 prerogative of the living organism? Is there 

 brought into action here a special cause, a kind of 

 life force? I think not, and incline much more 

 to the view that only the incompleteness of our 

 knowledge imparts to such processes the appear- 

 ance of the miraculous. 



No known facts are opposed to the view that 

 the plant, just as in chemical synthesis, produces 

 at first both forms, that it then separates the two 

 and that it uses the members of the (J-mannito 

 series for the formation of starch, cellulose, inu- 

 lin, etc., while the optical isomers serve for some 

 other yet unknown purpose. 



While Fischer's explanation may appear 

 plausible, nevertheless the fact that no 



