PROTOPLASMIC STRUCTURE 19 



theory obviously but transfers the biological problem from this planet 

 to some other. (4) For twenty centuries and more the theory of spon- 

 taneous generation was usually accepted, and Aristotle, founder of 

 biology, shared the belief. This notion was simply that life originated 

 continually from non-living matter. This was the natural and inevitable 

 conviction in days when there were no microscopes, or none powerful 

 enough to show the germs of animals. Today, without at all denying the 

 possibility, past, present, or future, of the spontaneous origin of life from 

 inorganic matter, we are almost satisfied to believe that every animal, 

 as also every plant, at present originates in one way or another only from 

 more or less similar living parents or parent. In other words, most 

 biologists nowadays suppose that protoplasm (and by the term proto- 

 plasm we mean all living matter) springs only from germs and germ- 

 plasm. (5) In 1866 Ernst Hackel suggested that from analogy it was 

 proper to assume that life, or at least living forms, did begin to develop 

 at some time or other in the earth's evolution from unorganized, non- 

 living matter. This is the supposition which at present receives the most 

 attention from biologists as the probably true theory. Pfliiger accepts 

 this hypothesis, and has materially developed it by suggesting (1875) that 

 in the vast chemical intermingling of the slowly cooling world there was 

 early a union of the elements carbon, hydrogen, oxygen, nitrogen, and 

 sulphur in a way which made possible the phenomena we called life 

 in the new substance so produced. Pfliiger, indeed, goes farther in 

 hypothesis, and postulates that the combination characteristic of life in 

 its last analysis is cyanogen (CN), the union of carbon and nitrogen. 

 All the decomposition-products of protoplasm (for example, urea, creatin, 

 guanin, uric acid) hold this cyanogen radicle or group, and this is good 

 evidence that living protoplasm always contains it also, while it is likely 

 that "dead protoplasm" does not. Cyanic acid, CNOH, Pfliiger points 

 out, is like protoplasm in many respects: it is fluid and transparent at 

 low temperature, coagulating by heat; both break up into carbon dioxide 

 and ammonia; and both produce urea by dissociation. "The similarity 

 of the two substances is so great that I might describe cyanic acid as a 

 semiliving molecule." Cyanogen and its compounds are formed only at 

 incandescent heat, such as surely obtained on the earth in its early 

 stages of cooling, and others of the components of protoplasm are made 

 under a like condition. Perhaps a further quotation of Pfliiger's words 

 will best represent his ideas: "Thus," he says, "nothing is clearer than 

 the possibility of the formation of cyanic compounds when the earth was 

 entirely or partially in a state of incandescence or great heat. We see 

 how extraordinarily all the facts of chemistry point to fire [see Heraclitus !] 

 as the force that has produced the constituents of albumin by synthesis. 

 Hence life was born from fire, and the chief conditions of its appearance 

 are associated with a time when the earth was a glowing ball of fire. 

 When we remember the incalculably long period in which the surface 

 of the earth was cooling, we see that cyanogen, and the compounds that 

 contained cyanogen, and carburetted hydrogen had sufficient time and 



