THE ORIGIN OF LIFE ARMSTRONG. 533 



cMefly the various amino-acids. The carbohydrate may be com- 

 pared with a house built of bricks alone, the albuminoids with a house 

 built partly of bricks and jjartly of stone slabs of various shapes and 

 sizes; the latter form of construction permits of a greater vaiiety of 

 pattern but the sa\ne building operations are involved in the use of 

 the two kinds of material; though the constructive units are differ- 

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

 of mortar in a similar way. 



The directive mfluences at work and which preside over synthetic 

 operations in the plant and animal cell are undoubtedly 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 enzjrmes is comparable with that of acids and 

 alkalies, the former especially, with the exception that enzymes act 

 selectively; but whereas acids will hydrolyze 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 comj^ounds; hence then- 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 mate- 

 rials and that in some way or other they are adaptable to the com- 

 pounds upon which they act. The picture I form of an enzyme is 

 that of a minute droplet of jelly to which 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 superabun- 

 dant 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 prac- 

 tically 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 wliich 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 

 85360°— SM 1912 35 



