"fHE COMING OF LIFE 3 



form the essential link in the round of organized material 

 stored up by the plant; eaten, used, and cast out by the 

 animal; and changed again into plant food by these micro- 

 scopic chemists. But they are not limited to this kind of food- 

 material. 



One of the greatest triumphs of modern science is the fixa- 

 tion, combination and utilization of atmospheric nitrogen, a 

 stubborn inert material which refuses, or is very slow, to 

 combine with other elements. The bacteria solved this prob- 

 lem millions of years ago; in root-tubercles, and in the soil 

 they are carrying on the same work to-day bare-handed, not 

 in great laboratories. It is probable that carbon, either in 

 the form of coal or charcoal, may be oxidized by certain of 

 the soil bacteria. Carbon, at any ordinary temperature, seems 

 even more inert than nitrogen. They are said to be able to 

 oxidize paraffine and other resistant compounds. All this 

 marvellous work of chemical analysis and synthesis goes on 

 in or around the bodies of minute bacteria whose only re- 

 agents are such as the protoplasm can manufacture in and 

 for itself. Every one is a marvellous synthetic laboratory, 

 building up more complex compounds out of simpler ones, 

 the work which modern chemists find most fascinating and 

 difficult. 



Their chief reagents in this synthetic work are the enzymes 

 which are capable of bringing about changes in various sub- 

 stances without becoming a part of the final product. They 

 seem to produce combinations without remaining in them; 

 hence are not used up, but theoretically may be used in- 

 definitely. A small amount of enzyme can do a large amount 

 of work and synthesize a great amount of material. They 

 are strange complex substances about which we still know 

 very little; but the bacteria produce them in great variety and 

 use them for many purposes. 



Says Osborn: "In their power of finding energy or food in 

 a lifeless world, the bacteria known as prototrophic, or ' prim- 

 itive feeders,' are not only the simplest known organisms but 

 it is probable that they represent the survival of a primordial 



