3 2o SCIENCE PROGRESS 



is attached a protuberance very closely resembling if not 

 identical with the group to which the enzyme can be affixed. 

 A geometer caterpillar attached by its hind legs to a twig, with 

 body raised so as to bring the mouth against a leaf on the twig, 

 affords a rough analogy, to my thinking, of the system within 

 which and within which alone an enzyme is active. 



In the beginning of things, carbonic acid was doubtless 

 superabundant and reducing agents were not far to seek: 

 under such conditions formaldehyde may well have been an 

 abundant natural product. The production of fructose sugar, if 

 not of glucose, would be practically a necessary sequence to that 

 of formaldehyde. 



But at this early stage, under natural conditions, gloves were 

 always made in pairs, left-hand and right-hand in equal 

 numbers ; by chance, somewhere, something happened by which 

 the balance was disturbed : some of the left-hand gloves were 

 destroyed perhaps. 



It is well known that if a crystal be placed in a saturated 

 solution of its own substance, the surface molecules will attract 

 like molecules from the solution and the crystal will grow. It 

 is not unlikely that a substance may exercise attraction over 

 molecules which are its own proximate constituents — that 

 glucose, for example, may exercise a preferential attraction over 

 molecules of formaldehyde ; if such be the case, glucose may itself 

 serve to influence and promote the formation of glucose from 

 formaldehyde. 



Granting such a possibility, if by some accident right-hand 

 molecules preponderated in a solution in which the conditions 

 were favourable to the synthesis of new molecules, the influence 

 of pattern would prevail and a larger proportion of right-hand 

 material would be formed. In course of time the left-hand 

 material would die out and only right-hand material would be 

 present— as in the world to-day. The argument is applicable 

 to compounds generally. 



Even the formation of enzymes may be accounted for. 

 Under the influence of acid or alkali, colloid particles may 

 well have entered into association with this or that group. 

 But when once formed fortuitously enzymes probably would 

 become the models or templates upon which new molecules 

 would be formed, much after the manner of the dressmaker's 

 model upon which the dress bodice is fashioned. 



