Mariel Manuel’s Notes 𝚿
The Theory of Spontaneous Generation
Aristotle (384-322 BC):
- Was one of the earliest recorded scholars to articulate the
theory of spontaneous generation, the notion that life can
arise from nonliving matter.
- Aristotle proposed that life arose from nonliving material if
the material contained pneuma (“Vital heat”).
Jan Baptista van Helmont(17th Century):
- Flemish scientist
- Proposed that mice could arise from rags and wheat kernels
left in an open container for 3 weeks.
- In reality, such habitats provided ideal food sources and
shelter for mouse populations to flourish.
Francesco Redi (1626-1697):
- Performed an experiment in 1668 that was one of the first
to refute the idea that maggots (the larvae of flies)
spontaneously generate on meat left out in the open air.
- He predicted that preventing flies from having direct
contact with the meat would also prevent the appearance of
maggots.
Redi left meat in each of six containers:
, Mariel Manuel’s Notes 𝚿
John Needham (1713-1781):
- In 1745, published a report of his own.
- He briefly boiled broth infused with plant or animal matter,
hoping to kill all preexisting microbes. He then sealed the
flasks. After a few days, Needham observed that the broth
had become cloudy and a single drop contained numerous
microscopic creatures. He argued that the new microbes
must have arisen spontaneously.
- In reality, however, he likely did not boil the broth enough
to kill all preexisting microbes.
Lazzaro Spallanzani (1729-1799):
- Did not agree with Needham’s conclusions, however, and
performed hundreds of carefully executed experiments
using heated broth.
- Heated but sealed flasks remained clear, without any signs
of spontaneous growth, unless the flasks were subsequently
opened to the air. This suggested that microbes were
introduced into these flasks from the air.
- Needham argued that life originates from a “life force” that
destroyed during Spallanzani’s extended boiling.
Louis Pasteur:
- A prominent French chemist who had been studying
microbial fermentation and the causes of wine spoilage,
accepted the challenge.
- In 1858, Pasteur filtered air through a gun-cotton filter and,
upon microscopic examination of the cotton, found it full of
microorganisms, suggesting that the exposure of a broth to
air was not introducing a “life force” to the broth but rather
airborne microorganisms.
- Made a series of flasks with long, twisted necks (“swan-
neck” flasks)
“Omne vivum vivo” (“Life only comes from life”).
The Theory of Spontaneous Generation
Aristotle (384-322 BC):
- Was one of the earliest recorded scholars to articulate the
theory of spontaneous generation, the notion that life can
arise from nonliving matter.
- Aristotle proposed that life arose from nonliving material if
the material contained pneuma (“Vital heat”).
Jan Baptista van Helmont(17th Century):
- Flemish scientist
- Proposed that mice could arise from rags and wheat kernels
left in an open container for 3 weeks.
- In reality, such habitats provided ideal food sources and
shelter for mouse populations to flourish.
Francesco Redi (1626-1697):
- Performed an experiment in 1668 that was one of the first
to refute the idea that maggots (the larvae of flies)
spontaneously generate on meat left out in the open air.
- He predicted that preventing flies from having direct
contact with the meat would also prevent the appearance of
maggots.
Redi left meat in each of six containers:
, Mariel Manuel’s Notes 𝚿
John Needham (1713-1781):
- In 1745, published a report of his own.
- He briefly boiled broth infused with plant or animal matter,
hoping to kill all preexisting microbes. He then sealed the
flasks. After a few days, Needham observed that the broth
had become cloudy and a single drop contained numerous
microscopic creatures. He argued that the new microbes
must have arisen spontaneously.
- In reality, however, he likely did not boil the broth enough
to kill all preexisting microbes.
Lazzaro Spallanzani (1729-1799):
- Did not agree with Needham’s conclusions, however, and
performed hundreds of carefully executed experiments
using heated broth.
- Heated but sealed flasks remained clear, without any signs
of spontaneous growth, unless the flasks were subsequently
opened to the air. This suggested that microbes were
introduced into these flasks from the air.
- Needham argued that life originates from a “life force” that
destroyed during Spallanzani’s extended boiling.
Louis Pasteur:
- A prominent French chemist who had been studying
microbial fermentation and the causes of wine spoilage,
accepted the challenge.
- In 1858, Pasteur filtered air through a gun-cotton filter and,
upon microscopic examination of the cotton, found it full of
microorganisms, suggesting that the exposure of a broth to
air was not introducing a “life force” to the broth but rather
airborne microorganisms.
- Made a series of flasks with long, twisted necks (“swan-
neck” flasks)
“Omne vivum vivo” (“Life only comes from life”).
