John Turberville Needham

1713-1781

English Naturalist

The English naturalist John Needham conducted a series of experiments that seemed to provide proof of spontaneous generation—the sudden appearance of organisms from nonliving materials. His work spurred that of Italian scientist Lazzaro Spallanzani (1729-1799), who conducted similar experiments, but had opposite results.

Needham was born in London in 1713. He left England in order to receive the education required for the Roman Catholic priesthood, which he completed in 1738. (Such schooling would have been difficult to obtain in England, which was under Protestant rule after a period of religious turmoil.) Rather than serve as a priest, however, Needham spent much of his life as a tutor to young English Catholics as they toured the European continent.

Needham had read about recent discoveries that had been made with microscopes, including the discovery of "animalcules" (which are now called microorganisms). He became fascinated with microscopy, the use of microscopes to make scientific observations. In 1745, he published An Account of Some New Microscopical Discoveries. This work included his observations of different types of pollen.

While studying microscopy in Paris, Needham became acquainted with Georges Buffon (1707-1788), a French naturalist who developed early ideas related to evolution. Buffon introduced Needham to some of the ideas of the German philosopher and mathematician Gottfried Wilhelm Leibniz (1646-1716). Leibniz had proposed the existence of living molecules, which he called monads. Needham not only accepted this idea, but he further believed that when organisms died and decayed, their individual molecules continued to live and could join together to form new living matter. He believed that a force, which he called the "vegetative force," brought these molecules together, much like oppositely charged atoms will be drawn together.

By Needham's time, it was generally accepted that animals could not form by spontaneous generation. However, the idea of spontaneous generation came into fashion with regard to "animalcules." Some naturalists did not believe that such tiny organisms would be able to produce even tinier offspring. They suggested that these organisms must therefore form spontaneously. Needham and Buffon were supporters of this view.

At Buffon's urging, Needham began a series of experiments in 1748 to test this hypothesis. He boiled broth containing meat and grain, presuming that the heat would kill any microorganisms that happened to be present. Then he poured the broth into glass containers and sealed them with corks. After several days, he opened the containers and looked at their contents under a microscope. He observed numerous microorganisms in the broth and concluded that they had arisen spontaneously from the nonliving material inside the containers. In 1750, he published a paper on the results of his findings.

Twenty years later, Lazzaro Spallanzani repeated Needham's experiments. He proposed that microorganisms had appeared in Needham's solutions because the containers were contaminated or because the broth had not been boiled long enough to be completely sterilized. In fact, Spallanzani found that some types of microorganisms could survive boiling for more than an hour. (Needham had boiled his broth for only a few minutes.) In addition, Spallanzani believed that Needham's containers were not necessarily airtight because they had been sealed with corks. To prevent this from happening, Spallanzani heated the ends of his containers and then pinched the softened glass together to form an airtight seal. No microorganisms appeared in Spallanzani's sealed vessels, and he concluded that spontaneous generation does not occur.

When Needham heard of these experiments, he repeated them as they were described in Spallanzani's published report. He quickly pointed out what he claimed were flaws in Spallanzani's procedures. Needham claimed that an hour of boiling would damage the vegetative force in the broth and prevent spontaneous generation from occurring. In addition, Needham heard air rushing into the sealed containers when he opened them. He claimed that this showed that the air inside the flasks had been damaged in some manner. (The rush of air was actually due to the heating of the glass as the seal was made.)

To counter Needham's arguments, Spallanzani conducted additional experiments. To show that the vegetative force (if it existed) was not damaged, he boiled broth for an hour and then left it exposed to the air. When he examined it a few days later, microorganisms had appeared. This showed that the broth was still capable of supporting life. To show that the air in the containers was not damaged, he designed a special flask with a long skinny neck that could be sealed very quickly. When he opened this container, no air rushed in. Therefore, the air could not have been damaged as Needham argued. Despite Spallanzani's experiments, Needham (and many other scientists) remained firmly convinced in the spontaneous generation of microorganisms. It was not until Louis Pasteur's (1822-1895) experiments in the nineteenth century that the question was finally settled.

In addition to his scientific work, Needham was also well-known for his writings on religion. In 1768, he was elected to the Royal Society, the oldest scientific society in Britain. In the same year, he moved to Brussels, Belgium, where he became the director of the Academy of Sciences. He died in Brussels in 1781.

STACEY R. MURRAY