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John Needham: Biography, Experiments & Cell Theory

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  • 0:04 Spontaneous Generation
  • 0:53 John Needham Background
  • 2:21 John Needham Experiments
  • 4:20 Cell Theory
  • 5:47 Lesson Summary
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Lesson Transcript
Instructor: Shelly Watkins

Shelly has instructed college biology courses, as well as graduate students in health profession programs. She has a doctorate in physical therapy.

In this lesson, we'll discover the accomplishments and biography of John Needham, including his important experiments and contributions to the cell theory.

Spontaneous Generation

In the past, people thought that frogs were spontaneously created from mud and that maggots arose directly from rotting meat. These ideas weren't possible for many reasons, one being the fact that only cells can give rise to living organisms. The fact that only cells are able to produce more cells is part of cell theory.

The idea that organisms can develop independently of cells is called spontaneous generation, and it isn't supported by cell theory. Spontaneous generation suggests that living organisms develop from non-living matter. One of the earliest recorded scholars to propose this theory was the Greek philosopher Aristotle. Biologist John Needham was a proponent of spontaneous generation, but his research ultimately provided support to the development of cell theory.

John Needham Background

John Turberville Needham was born in London on September 10, 1713. He was a Roman Catholic priest, but he primarily worked as a teacher and tutor. Needham studied at the English College at Douai in France. He taught at several schools, including a college in Cambrai, France; a Catholic school near Twyford, Winchester; and a school in Lisbon, Portugal. Ultimately, he became director of the Brussels Academy. Needham was a microscopist, and his early work included microscopic observations of tainted wheat and investigations into squid organs. In 1747, he was the first Catholic priest elected to the Royal Society of London.

Needham's research was published in An Account of Some New Microscopical Discoveries and Observations upon the Generation, Composition and Decomposition of Animal and Vegetable Substances. From his research, Needham concluded that microorganisms don't actualy come from eggs, so he believed that his research supported the theory of spontaneous generation.

One of Needham's harshest critics included the philosopher Voltaire. Since Needham suggested that tiny microscopic animals could be created spontaneously in a sealed container, Voltaire believed that Needham's ideas could support atheism. Despite his critics, Needham made important contributions to the field of botany. After a colorful career, he died at the age of 68 on December 30, 1781.

John Needham Experiments

In 1745, John Needham briefly boiled broth, which contained both plant and animal matter. He believed this brief period of boiling would kill any microorganisms living in the broth. After sealing the broth mixture in a flask, he let it sit for three days. After this period, the broth was cloudy and Needham used a microscope to observe microbes present in the mixture. Needham concluded that these tiny organisms had spontaneously generated from the non-living matter of the broth.

Later, Lazzaro Spallanzani conducted a similar experiment with results that contradicted Needham's. Spallanzani boiled his mixtures for longer, and no microbes showed up in his sealed flasks. He suggested that the microbes found in unsealed broth samples came from microbes in the air. To develop on this idea of microbes in the air, French chemist Louis Pasteur performed a test by passing air through cotton filters, which trapped tiny particles in the air. The cotton was dissolved in ether and alcohol, and the air particles settled in the liquid. Pasteur determined that if these particles, which were found to be bacteria, were existent in the air then they would contaminate any exposed material.

Both Spallanzani's and Pasteur's work disproved Needham's broth experiment and its support for spontaneous generation. Needham's broth experiment had two fundamental flaws. First, his boiling time was not sufficient to kill all microbes. Second, his flasks were left open as they cooled, and exposure to the air could cause microbial contamination.

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