Life Viewed Through the Microscope

In 1590 Zacharias Janssen invented the microscope. Johannes Kepler and Christoph Scheiner soon made improvements on this invention. Then, in 1676, Anton van Leeuwenhoek, a Dutch dry-goods merchant who manufactured his own microscopes, presented a paper before the Royal Society of London in which he claimed to have discovered “wee beasties” under his microscope’s lenses.

Here, then, was microscopically sized life; and while the spontaneous generation of maggots had been disproven, and the “creation” of mice by rags in a dark corner seemed unlikely, surely these extremely small creatures must have arisen from a nonliving precursor. In 1749 John Needham devised an experiment that seemed to confirm this theory. He prepared a broth in which grew great numbers of tiny organisms. He then brought the broth to a boil and determined that all the organisms were destroyed through boiling. After letting the broth stand for a day or two, he observed that the creatures reappeared. This was interpreted as a proof of the spontaneous generation of life.

Lazzaro Spallanzani (1729-1799) was a skilled experimenter who studied blood circulation, respiration, digestion, the senses of bats, and the breeding of eels. His name belongs here, however, because of his experiments with bacteria. He repeated John Needham’s experiments. But after boiling the broth to destroy the microorganisms, he drew out the neck of the flask and sealed it against any further invasion by organisms. When he broke open the flask after several days and examined the contents for microorganisms, none could be found. This may appear to be a turning point in the study of the origin of life. Another hundred years would pass before Louis Pasteur’s series of experiments in 1859 finally put to rest the concept of spontaneous generation of life.