associated with living matter, but his task has included the attempt to account for the molecular forms of certain ãasymmetricã substances, glucose, malic acid and many more, as they occur in nature. These are bodies which, when artificially synthesised, have no optical activity, but which, as we actually find them in organisms, turn (when in solution) the plane of polarised light in one direction or the other; thus dextro-glucose and laevomalic acid are common products of plant metabolism; but dextromalic acid and laevo-glucose do not occur in nature at all. The optical activity of these bodies depends, as Pasteur shewed more than fifty years ago9, upon the form, right-handed or left-handed, of their molecules, which molecular asymmetry further gives rise to a corôÙreôÙsponôÙding right or left-handedness (or enantiomorphism) in the crystalline aggregates. It is a distinct problem in organic or physiological chemistry, {417} and by no means without its interest for the morphologist, 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 phenomenon has its origin in ãfortuity,ã than to repeat the Abbûˋ Galianiãs saying, ãles dûˋs de la nature sont pipûˋs.ã
The problem is not so closely related to our immediate subject that we need discuss it at length; but at the same time it has its clear relation to the general question of form in relation to vital phenomena, and moreover it has acquired interest as a theme of long-continued discussion and new importance from some comparatively recent discoveries.
According to Pasteur, there lay in the molecular asymmetry of the natural bodies and the symmetry of the artificial products, one of the most deep-seated differences between vital and non-vital phenomena: he went further, and declared that ãthis was perhaps the only well-marked line of demarcation that can at present [1860] be drawn between the chemistry of dead and of living matter.ã Nearly forty years afterwards the same theme was pursued and elaborated by Japp in a celebrated lecture10, and the distinction still has its weight, I believe, in the minds of many if not most chemists.
ãWe arrive at the conclusion,ã said Professor Japp, ãthat the production of single asymmetric compounds, or their isolation from the mixture of their enantiomorphs, is, as Pasteur firmly held, the prerogative of life. Only the living organism, or the living intelligence with its conception of