THE ORIGIN OF LIFE: A CHEMIST'S FANTASY 319 



that, excepting a few which presumably are products of retro- 

 grade changes, they are all of one type — right-hand material ; 

 and apparently they stand in close genetic connexion. 



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 differ- 

 ence between the two classes of compound is that whereas the 

 sugars are composed of like simple units, the albuminoids consist 

 of unlike simple units, chiefly the various amino-acids. The 

 carbohydrate may be compared with a house built of bricks 

 alone, the albuminoids with a house built partly of bricks and 

 partly of stone slabs of various shapes and sizes ; the latter form 

 of construction permits of a greater variety of pattern but the 

 same building operations are involved in the use of the two kinds 

 of material : though the constructive units are different, in both 

 cases, the pieces are placed in position and fixed by means of 

 mortar in a similar way. 



The directive influences at work and which preside over 

 synthetic operations in the plant and animal cell are un- 

 doubtedly the enzymes : these apparently serve as templates 

 and either promote synthesis by dehydration or the reverse 

 change of hydrolysis, according as the degree of concentration 

 is varied. 



But how, it will be asked, could action have taken place in 

 times prior to the existence of enzymes? What are enzymes and 

 how did they arise ? 



The activity of enzymes is comparable with that of acids and 

 alkalies, the former especially, with the exception that enzymes 

 act selectively ; but whereas acids will hydrolyse every kind of 

 ethereal compound and are active in proportion to their strength 

 and the concentration of the solution in which they are 

 operative, enzymes will act only on particular compounds: hence 

 their special value as "vital " agents. And the same distinction 

 is to be made with respect to the synthetic activity of the two 

 groups of agents. 



At present our knowledge of enzymes is vague : we know 

 little of their structure. At most we can assert that they are 

 colloid materials and that in some way or other they are 

 adaptable to the compounds upon which they act. The picture 

 I form of an enzyme is that of a minute droplet of jelly to which 

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