532 ANNUAL KEPOET SMITHSONIAN INSTITUTION, 1912. 



polarized light in opposite directions, though to an equal extent, they 

 may be said to be half right-hand and half left-hand material. 



Two other hexose sugars isomeric with glucose occur naturally — 

 galactose and mannose; but the three compounds all belong to the 

 one series and all may be said to be right-hand material. 



Besides these three hexose sugars, plants also contain the ketose, 

 fructose, which is isomeric with glucose and differs from it only in 

 contammg the CO group as the second instead of as the terminal 

 member in the chain of radicles composing the molecule: 



CH2(0H). CH(OH). Cn(OH). CH(OH). CO. CHo. OH. 



Fructose is convertible into glucose, and vice versa. Natural fructose 

 and glucose are both right-hand material. Nature apparently is 

 smgle handed and can make and wear only right-hand gloves. 



It is possible to prepare such compounds in the laboratory from 

 the simplest materials, starting from carbonic acid — C0(0H)2 — the 

 compound from which the plant derives carbon. By reduction this 

 is first converted into formaldehyde, COHj. Wlien digested with 

 weak alkali, this aldehyde is in part converted into fructose; the 

 fructose that is formed, however, is not merely the form which is 

 found in plants but a mixture of this with an equal proportion of 

 the left-hand form. When the chemist makes gloves, he usually can 

 not help makmg them in pairs for both hands. 



Some directive influence is clearly at work in the plant — the for- 

 maldehyde molecules, which it undoubtedly makes use of as primary 

 buildmg material, in some way become so arranged that when they 

 interact they give only the right-hand form of sugar. There is reason 

 to thmk, moreover, that the action takes place only in this one direc- 

 tion — that the sugar is the only product. My own belief is that the 

 synthesis is effected agamst a sugar template ^ just as a brick arch 

 is built upon a wooden template curved as the arch is to be curved. 



A similar argument is applicable to the albummoid or protein mat- 

 ters derived from animal and vegetable materials; in fact, to nearly 

 all the natural optically active substances ; these are all formed under 

 directive influences. It is not improbable that, exceptmg a few which 

 presumably are products of retrograde clianges, they are all of one 

 type — right-hand material — and apparently they stand in close genetic 

 connection. 



Prof. Minchin has difficulty, he says, in understanding how the 

 complex proteins could have arisen in nature. But the difficulty in 

 accounting for these is no greater than that involved in accounting 

 for the formation of the sugars. The chief difference between the 

 two classes of compound is that whereas the sugars are composed of 

 like simple imits, the albuminoids consist of unlike simple lyiits, 



» Proceedings of the Royal Society, 1904, vol. 73, 541. 



