SCIENTIFIC USE OF THE IMAGINATION 133 



play an important part. To two men, one educated in 

 the school of the senses, having mainly occupied himself 

 with observation; the other educated in the school of 

 imagination as well, and exercised in the conceptions of 

 atoms and molecules to which we have so frequently re- 

 ferred, a bit of matter, say rooooth of an inch in diameter, 

 will present itself differently. The one descends to it from 

 his molar heights, the other climbs to it from his molecu- 

 lar lowlands. To the one it appears small, to the other 

 large. So, also, as regards the appreciation of the most 

 minute forms of life revealed by the microscope. To one 

 of the men these naturally appear conterminous with the 

 ultimate particles of matter; there is but a step from the 

 atom to the organism. The other discerns numberless 

 organic gradations between both. Compared with his 

 atoms, the smallest vibrios and bacteria of the micro- 

 scopic field are as behemoth and leviathan. The law of 

 relativity may to some extent explain the different atti- 

 tudes of two such persons with regard to the question of 

 spontaneous generation. An amount of evidence which 

 satisfies the one entirely fails to satisfy the other; and 

 while to the one the last bold defence and startling ex- 

 pansion of the doctrine by Dr. Bastian will appear per- 

 fectly conclusive, to the other it will present itself as 

 merely imposing a labor of demolition on subsequent 

 investigators. l 



Let me say here that many of our physiological ob- 

 servers appear to form a very inadequate estimate of the 

 distance which separates the microscopic from the mo- 

 lecular limit, and that, as a consequence, they sometimes 



1 When these words were uttered I did not imagine that the chief labor 

 of demolition would fall upon myself. 1878. 



