Leeuwenhoek, whom Paul de Kruif has called "the "First of the Microbe Hunters" died in 1723. the publication of his letters with micrographs of bacteria, molds, and protozoa, by the Royal Society was the forerunner of our modern scientific journals. The world was aware of the "animalcules" because of Leeuwenhoek's work, but there was no immediate successor to Leeuwenhoek. There was no attempt to connect them in any way with disease. As a matter of fact, scientists and public at that time thought they simply arose spontaneously almost anywhere there was warmth, air and water.

The leading scientists of that era believed that "to question that beetles and wasps are generated in cow dung is to question reason, sense, and experience. " Even mice were believed to arise spontaneously where there was debris with moisture and warmth. Lazzaro Spallanzani would continue where Leeuwenhoek stopped in the study of microscopic life.

As a boy, Spallanzani loved to roam through the woods. When he saw natural fountains springing from the earth he was told by his priest that this was from the "tears of sad, deserted beautiful girls who were lost in the woods". But, even as a boy he had unboyish thoughts challenging such concepts. Although his father wanted him to study law, he secretly worked on mathematics, Greek, French and Logic, hoping to get into science. He also went to a noted scientist and told him what he was working on; this scientist persuated his father to send him to the University of Reggio and let him begin a career in science. It was now more respectable to go into science than in Leeuwenhoek's day. The Grand Inquisition was now torturing heretics rather than persecuting scientists such as Gallileo. Voltaire, the great French leader, even studied the discoveries of Newton and popularized them in his country.

Very early, Spallanzani had strong ideas about spontaneous generation. Although the prominent scientists of his day believed and taught it, Spallanzani did not. First of all, he read the report of a scientist named Francisco Redi who put meat in two laboratory jars, one of them covered by cheesecloth. Redi observed that flies laid eggs on the uncovered meat, which hatched out into maggots, which then became adult flies. Spallanzani decided that instead of arguing, he would try an experiment with Leeuwenhoek's "animalcules." With difficulty he obtained a microscope and learned how to use it.

Spallanzani was an Italian priest, as priests made up a large proportion of the professors in the Universities of that day. He became a participant in a great debate with an Irish priest and educator, Needham. Needham was also an experimenter with the "wee beasties". Needham brought to the Royal Society reports on a series of experiments with mutton gravy. He also used seeds, crushed almonds and other media. After closing with "mastic"and heating the flask he opened it to find it swarming with "animalcules," observed by the microscope. The Royal Society and scientists generally, accepted the reports as proof of spontaneous generation of all microscopic life. It was believed that the heating destroyed any life that might have been in the soups, but that, with air and warmth, microscopic life arose again, "spontaneously."

Spallanzani did not believe this, but he was almost alone in his rejection of the concept and knew that he must design experiments that would demonstrate the truth, as to whether he or Needham was right. He decided that Needham had not "cooked" the soups long enough, so he boiled the flasks for an hour. He also developed methods of sealing the necks of the flasks with glass rather than using corks and "mastic" After leaving the flasks for various lengths of time, Abbe Spallanzani opened them and examined the contents under the microscope. No microbes! He thus became the first to preserve of can soup.

The great debate between the two priests began. Needham had a wealthy supporter, French Count Buffon. Count Buffon enjoyed science and scientists. He asked "Father Needham" what causes the "animalcules" to arise out of the mutton gravy and other soups. "My Lord, it is a Vegetative Force", Father Needham replied and the name stuck. All the scientists of Europe were now talking about "Vegetative Life Force." The Royal Society accepted the experiments and the lectures and made Needham a Fellow of the Society. Needham and the wealthy Count Buffon published and lectured widely. The French Academy of Science made Needham an Associate.

Spallanzani was a priest who believed strongly in God. He also believed that God supported the truth. Father Needham had even stated that it was "A Vegetative Force" that made Eve grow from Adam's rib. All of this was nonsense to Spallanzani, but he had to find a way to meet his fellow priest's pretty words with facts. He was able to demonstrate that when properly heated in sealed flasks, no soups of any kind supported life, but when contaminated air was admitted the life appeared. No "Vegetative Force" was needed.

This was finally accepted by the scientists of Europe, but the question still arose: "where do the microbes come from?" Observation by the microscope often showed two bacteria or other organisms, side by side. Some thought there might be a form of mating, as in higher forms of life. Others thought that in their violent movements in the liquid media a bacterium might strike another one and break it into two. One of the triumphs of Spallanzani's experimental method was his development of what we call today a "pure culture." He set himself the task of trying to isolate a single bacterium in clear medium and watch it divide under the microscope.

He finally was able to segregate just one tiny bacterium under his lens. No other bacterium could jostle it or break it and there was no other to mate with it. His excitement knew no bounds when he saw the single cell begin to elongate, then, pinch off into two cells, identical, but each slightly smaller than the original. Soon,these two became normal in size and divided as did the first one. He repeated this experiment a dozen times before publishing it to the astonishment of scientists of his time.

Spallanzani's life and brilliant struggles against the false concepts of leading scientists of his day have been eclipsed by the stories of tha famed Pasteur and Koch. But he was a worthy successor to the great Leeuwenhoek. His courage in the face of ridicule by scientific leaders and his creative skill as a microbiologist in demonstrating clearly that microbial life arose from microbial life are examples worthy of emulation, even today.