TRANSACTIONS OF SECTION B. 823' 



is the conversion of r7-mannose by combination with Iiydvocyanic acid into tbe' 

 nitrile ofii-mannoheptonic acid, studied by Erail Fischer, in wbich only one nitrile 

 is formed, although there are two ways in which the hydrocyanic acid may attach' 

 itself to the aldehyde group of the mannose. On the other hand, the same general 

 reaction, in the union of hydrocyanic acid with ordinary aldehyde Clla.CHO 

 — a symmetric compound — yields the right and left forms of lacto-nitrile' 

 033.(711(011). ON in equal quantity, the two asymmetric events occurring iu' 

 equal number, and the resulting mixture of compounds being inactive. It is the 

 ditlerence between guidance and no guidance : the asymmetric group present in 

 the mannose guides into a particular path the symmetric forces which bring about' 

 the addition of the hydrocyanic acid ; in the case of the symmetric aldehyde the' 

 result is left to pure chance. The latter action is like that of tossing a perfectly 

 balanced coin ; in the former the coin is heavily weighted on one side. The say- 

 ing, ' les des dc la Nature sont pipes,' is certainly true of living Nature and its 

 products. 



This guiding action displayed by asymmetric compounds may even impart a 

 bias to the crystallisation of those molecularly symmetric substances already 

 referred to, which crystallise in enantiomorphous forms. Thus, Kipping and Pope 

 have recently made the interesting observation that the crystals of sodium chlorate 

 which are deposited from an aqueous solution containing 200 grams of <^-glucose 

 to the litre consist, on an average, of about 32 per cent, of right-handed to 68 pei' 

 cent, of left-handed crystals, the asymmetric carbohydrate, by its mere presence, 

 favouring the formation of the one asymmetric form of the inorganic salt at the 

 expense of the other. 



These ob.servations possibly afford a clue to the mode of action of the living 

 organism in producing single enantiomorphs. This production of single asym- 

 metric forms may be a result of the asymmetric character of the chemical com- 

 pounds of which the tissues of plants and animals are built up. The optically 

 active products of the organism — the carbohydrates, the terpenes, tartaric acid, 

 asparagine, quinine, the serum of the blood, and countless others — have been 

 formed in an asymmetric environment, and their asymmetry is an induced pheno- 

 menon. They luive been cast, as it were, in an asymmetric mould. According to 

 this view they are a result of the selective production of one of the two possible 

 enantiomorphous forms. The same would hold good with regard to the organised 

 tissues themselves, developed from inherited asymmetric beginnings in the ovum 

 or the seed, or obtained by fission. The perplexing question of the (ib^olute origi)^ 

 of these asymmetric compounds I will discuss later. 



Another view has been put forward by Emil Fischer. In his lecture on 

 'Syntheses in the Sugar Group,' delivered before the German Chemical Society in 

 1890, he says : 



' Starting with formaldehyde, chemical synthesis leads, in the first instance, to 

 the optically inactive acrose. In contradistinction to this oiJy the active sugars 

 of the f7-mannitol series have hitherto been found in plants. 



' Are these the only products of assimilation [of carbon dioxide and water] Y 

 Is the preparation of optically active substances a prerogative of the living 

 organism ; is a special cause, a Idnd of vital force, at work here ? I do not think 

 so, and incline rather to the view that it is only the imperl'eetiou of our knowledge 

 which imports into this process the appearance of the miraculous. 



' No fact hitherto known speaks against the view that the plant, like chemical 

 synthesis, first prepares the inactive sugars ; that it then resolves them into their 

 active constituents, using the members of the cZ-mannitol series in building up 

 starch, cellulose, inulin, &c., whilst the optical isomerides serve for other purposes 

 at present unknown to us.' 



There are, therefore, two opposite processes which would account for the pre- 

 sence of optically active compounds among the substances generated in the living 

 organism, and which we may brietly describe as selective pvodiiction and seleetivi- 

 consum2)tiou. An instance of artificial selective pi-oduction is the formation of 

 onh' one nitrile of <?-mannoheptonic acid already cited. Selective consumption, 



