400 THE LIFE OF MATTER. 



attcinptino' to find more or less erude (.'([uivalents for them in l)i'ute 

 bodies or in ecrtain of them. 



Decisive veri/ficatkm — Spontaneous generation. — The rapid and deei- 

 sive method, which unhappii3'is beyond our resources, would consist in 

 showing' unquestionable, clearly marked life, the superior life, arising- 

 from the kind of inferior life that is attributed to matter in general. 

 It would only be necessary to completely construct in all its parts, b}" 

 a suitable combination of inorganic materials, a single living l;eing, 

 even the humblest plant or the most rudimentary animal. This would 

 indeed be an irrefutable proof that the germs of all vital activity are 

 contained in the molecular activity of brute bodies and that there is 

 nothing essential to the latter that is not found in the former. 



L'nluippily this demonstration can not be given. Science furnishes 

 no example of it, and we are forced to have recourse to the slow method. 



The question here involved is that of spontaneous g-eneration. It is 

 well known that the ancients believed in spontaneous generation even 

 for animals high in the scale of organization. According* to Van 

 Helmont, mice could be born by some incomprehensible fermentation 

 in dirty linen mixed with wheat. Diodorus speaks of animal forms 

 which were seen to emerge partly developed from the mud of the Nile. 

 Aristotle believed in the spontaneous birth of certain fishes. Rejected 

 as to the higher forms of animals, this belief was for a long time held 

 with regard to the lower ones, such as bees, which the shepherd of 

 Virgil saw coming out from the flanks of the dead bullock; such as 

 flies engendered in putrefying meat; such as fruit worms and intestinal 

 worms; finally with regard to infusoria and the most rudimentar}^ 

 vegetables. The hypothesis of spontaneous generation of the living- 

 being at the expense of the materials of the environment has been 

 successively driven from one classificatory group to another. The 

 histor}^ of the sciences of observation is also a history of the defejits 

 of this doctrine. Pasteur gave it the flnishing stroke when he show^ed 

 that the simplest micro-organisms obeyed the general law which 

 declares that a living being is formed only by filiation; that is to say, 

 by the intervention of a preexisting living organism. 



Spontaneous generation was an episode In the Jilstory of t/tr glot>r. — 

 Though we have been unable to effect spontaneous generation in the 

 present time, it has been put back, by Haeckel, into a more or less dis- 

 tant past, to the moment when the cooling- of the globe, the solidifica- 

 tion of its crust, and the condensation of aqueous vapor upon its sur- 

 face created conditions compatible with the existence of living beings 

 similar to those with which we are acquainted. Lord Kelvin has tixed 

 these geologic events as occurring from twenty to forty millions of years 

 ago. Then circumstances becatne propitious for the appearance of the 

 first organisms whence were successively derived those which now 

 people the earth and the waters. 



