650 ON CONCRETIONS, SPICULES, ETC. [ch. 



cretion and the hypothetical form of an individual molecule. But 

 molecular form is a very important concept; and the chemist has 

 not only succeeded, since the days of Wohler, in synthetising many 

 substances which are characteristically associated with living matter, 

 but his task has included the attempt to account for the molecular 

 forms of certain "asymmetric" substances — glucose, malic acid and 

 many more — as they occur in Nature. These are bodies which, when 

 artificially synthetised, have no optical activity, but which, as we 

 actually find them in organisms, turn (when in solution) the plane 

 of polarised hght in one direction rather than the other; thus 

 dextroglucose and laevomahc acid are common products of plant 

 metabohsm, but dextromalic acid and laevoglucose do not occur in 

 Nature at all. The optical activity of these bodies depends, as 

 Pasteur shewed eighty years ago*, upon the form, right-handed or 

 left-handed, of their molecules, which molecular asymmetry further 

 gives rise to a corresponding right- or left-handedness (or enantio- 

 morphism) in the crystalline aggregates. It is a distinct problem 

 in organic or physiological chemistry, and by no means without its 

 interest for the norpholonrist, to discover how it is that Nature, for 

 each particular substance, habitually builds up, or at least selects, 

 its molecules in a one-sided fashion, right-handed or left-handed as 

 the case may be. It will serve us no better to assert that this pheno- 

 menon has its origin in "fortuity" than to repeat the Abbe Galiani's 

 saying, ''les des de la nature sont pipes.'' 



The problem is not so closely related to our immediate subject 

 that we need discuss it at length; but it has its relation, such as it 

 is, to the general question oi form in relation to vital phenomena, 

 and it has its historic interest as a theme of long-continued discussion. 

 According to Pasteur, there lay in the molecular asymmetry of 

 the natural bodies and their symmetry when artificially produced, 

 one of the most deep-seated differences between vital and non- vital 

 phenomena: he went further, and declared that "this was perhaps 

 the only well-marked line of demarcation th'at can at present [1860] 

 be drawn between the chemistry of dead and of living matter." 

 Nearly forty years afterwards the same theme was pursued and 



* Lectures on the molecular asymmetry of natural organic compounds, Chemical 

 Soc. of Paris, 1860; also in Ostwald's Klassiker d. exact. Wiss. No. 28, and in 

 Alembic Club Reprints, No. 14, Edinburgh, 1897; cf. G. M. Richardson, Foundations 

 of Stereochemistry, New York, 1901. 



