3 of 103 of 10 Items 03:45 Question Theory of Spontaneous Generation From the time of the ancient Romans until the late nineteenth century, it was accepted that life arose spontaneously from non-living matter. Spontaneous generation is the hypothesis that some vital force contained in or given to organic matter can create living organisms from inanimate objects. There was a strong bias to legitimize the idea because this vital force was considered a strong proof of God's presence in the world. In 1745, John Needham proposed what he considered the definitive experiment in support of spontaneous generation. People believed that boiling killed microorganisms, so he proposed to test whether or not microorganisms would appear spontaneously after boiling. Needham boiled chicken broth, put it into a flask, sealed it, and waited. Microorganisms grew. Needham claimed victory for spontaneous generation. Biogenesis theory – Francesco Redi made the first scientific attack on spontaneous generation in 1668. At that time, it was believed that maggots arose spontaneously in rotting meat. Redi believed that maggots developed from eggs laid by flies. To test his hypothesis, Redi designed a controlled scientific experiment in which he set out meat in flasks, some open to the air, some covered with gauze, and others sealed completely. As Redi predicted, maggots appeared only in the open flasks in which flies could reach the meat and lay eggs. Following these experiments, an Italian priest, Lazzaro Spallanzani, suggested that perhaps the microorganisms had entered the broth from the air after Needham boiled the broth but before the container was sealed. To test his theory, Spallanzani modified Needham's experiment: he placed the chicken broth in a flask, sealed the flask, drew off the air to create a partial vacuum, and then boiled the broth. No microorganisms grew. In spite of this controlled scientific experiment, the belief in spontaneous generation remained strong until Louis Pasteur’s 1859 experiment. Pasteur boiledmeat broth in two flasks, then heated the neck of the flasks in a flame until they became pliable and bent it into an “S” shape. Air could enter the flask, but microorganisms could not. They settled in the crook of the S shaped neck due to gravity. As Pasteur expected, no microorganisms grew. When Pasteur broke the neck off of one of the flasks so the air could reach the broth, the broth became cloudy due to microbial growth. Pasteur had both refuted the theory of spontaneous generation and demonstrated that microorganisms are everywhere, even in the air.

What was the rationale for Spallanzani producing a partial vacuum?