Highlights in the History of Microbiology 21 



Research continued in an effort to devise some means of in- 

 creasing useful magnifications without sacrificing resolving power 

 (the ability to detect small objects that are close together), and 

 this resulted in the development of the electron microscope in 

 which electrons replace light waves. The wavelength of an 

 electric beam is about 1/100,000 that of light, and the Radio 

 Corporation of America developed an electron scope with mag- 

 nification as high as 100,000 diameters in one of the earliest 

 attempts to employ this new principle. Recent improvements have 

 pushed these limits up to 200,000 diameters, whereas the practical 

 limits of optical scopes is 2500-3000 diameters. Certain magnetic 

 and electric fields act on an electric beam in the same manner that 

 a lens acts on a light beam. High velocity electrons and electro- 

 magnetic or electrostatic "lenses" serve in place of the condenser, 

 objective, and ocular of optical instruments. The image produced 

 is viewed on fluorescent screens or is registered on a photographic 

 plate. 



THEORIES CONCERNING SPONTANEOUS GENERATION 



Having developed the tools necessary to see these microscopic 

 plants we know as bacteria, a second major problem confronting 

 biologists was the question of the origin of life. Could living 

 things arise spontaneously from dead matter ( abiogenesis ) , or do 

 all living things have to have parents (biogenesis)? While at- 

 tempting to thrash out the solution, many discoveries were made 

 which were incidental to the main objective, but which contributed 

 greatly to the over-all growth of the science of microbiology. 



It is just as true today as it was centuries ago that certain 

 persons greatly influence the thinking and the beliefs of their 

 time. Almost all so-called scientists from the time of Aristotle 

 (384-322 B.C.) to the middle of the nineteenth century, believed 

 that animals could be generated from non-living matter. The 

 ancient teachings of Aristotle were accepted, unfortunately, and 

 because of the man's stature, progress along certain lines was 

 materially retarded. According to this Greek naturalist, living 

 things were the result of passive matter and active form, the latter 



