50 SECTIONAL ADDRESSES 



activity of living matter. It was a subject to which Pasteur devoted much 

 thought, and he was disposed to seek the origin of the optical activity of 

 the products of vegetable life in cosmic causes. 



' The universe,' he said, ' is a dissymmetrical whole. I am inclined 

 to think that life, as manifested to us, must be a function of the dis- 

 symmetry of the universe or of the consequences that result from it. 

 The universe is dissymmetrical ; for, if the solar system were placed 

 before a mirror, the image of the bodies that compose it moving with their 

 several motions could not be superposed on the reality. Even the move- 

 ment of solar light is dissymmetrical. A luminous ray never falls without 

 constant change of direction on the leaf in which vegetable life is bringing 

 about the creation of organic matter. Terrestrial magnetism, the 

 opposition which exists between the north and south poles in a magnet, 

 that offered us by the two electricities positive and negative, are but 

 resultants from dissymmetrical actions and movements.' 



Pasteur tried to obtain experimental confirmation of these views. At 

 Strasburg he had powerful magnets constructed with the object of 

 introducing dissymmetric influences during the formation of crystals. 

 At Lille again, in 1854, he had a clockwork arrangement made by means 

 of which he intended, with the aid of a heliostat and reflector, to cause a 

 plant to germinate and grow under conditions in which the natural 

 apparent movement of the sun from east to west was reversed. 



Since the discovery by Cotton in 1896 that alkaline solutions of copper 

 tartrate have unequal coefficients of absorption for dextro- and leevo- 

 circularly polarised light, the action of circularly polarised light appeared 

 to be the most promising method of obtaining molecularly dissymmetric 

 compounds in an optically active state without the use of other optically 

 active substances. Since, further, circularly polarised light must occur 

 in nature — as, for example, by reflexion of the plane polarised part of the 

 light of the sky at the surface of the sea — the unequal destruction which 

 it must effect of the dextro- and laevo-forms of dissymmetric compounds, 

 acting for immense periods of time, has been regarded by some as the 

 most probable cause of the optical activity of the compounds contained 

 in living matter, especially as Byk has shown that, in consequence of the 

 rotation of the plane of polarisation of the light by the earth's magnetism, 

 there must be a preponderance of one of the two forms in the total amount 

 of circularly polarised light thus produced. 



These considerations have been brought into prominence by the marked 

 success which has recently been attained by Werner Kuhn and Knopf 

 in activating the dimethylamide of a-azidopropionic acid by means of 

 circularly polarised light. Kuhn has discussed the biological significance 

 of this achievement, and he gives reasons to show that the possibility of 

 the optical activity of living matter having been brought about through 

 the long-continued action of circularly polarised light can by no means 

 be rejected. 



When one considers, however, the minuteness of the proportion of the 

 total illumination received by an organism under natural conditions that 

 can be circularly polarised, and the difficulty that has been experienced 

 in demonstrating the optically activating effect of this form of light, even 



