Spontaneous Generation and The Cell Theory
Spontaneous Generation was the scientific theory that "lower life forms" (frogs, mice, verman, worms, insects, etc.) came from abiotic things. For example, mice came from the combination of sweaty clothing and wheat, maggots came from rotting meat, worms came from the dirt, and so on.
In 1668, Francesco Redi performed an experiment with rotting meat to show that maggots came from flies and not the meat itself. He put rotting meat in an open mouth container, a totally closed container, and a container that was covered with gauze (so the smell would come out but the flies couldn't get in). The results were that the flies flew into the open container and landed on the meat, they didn't do anything with the closed container, and they landed on the gauze. Maggots formed on the open rotting meat and on the gauze- proving that flies laid eggs that turned into maggots! Still, even Redi thought that some things did spontaneous generate from the matter around them.
In 1745, two priests performed nearly the same experiment to prove and disprove Spontaneous Generation. One, and Englishman named Needham boiled broth, placed it in a flask and sealed the flask (with air inside it). The broth got moldy and full of bacteria. The other, an Italian named Spallanzanni, did the same experiment BUT vacummed out the air. In this case, nothing grew in the broth UNTIL he removed the lid. Supporters of Spontaneous Generation simply scoffed and said that, of course, spontaneous generation of life requires air!
Lastly, in 1859, Louis Pasteur "killed" Spontaneous Generation by performing an experiment in which air could get in to the boiled broth but the stuff in the air could not. Nothing grew. When the broth was exposed to the things in the air (at the bottom of the S-tube, fungus and bacteria grew)! This showed that life was already in the air and that it did not spontaneous generate in the broth or the air itself.
Pasteur's experiment left a hole in the science of life. That hole was filled with The Cell Theory.
The Cell Theory
1. All living things contain cells (Robert Hooke, 1665)
2. All plants have cells (Schleiden, 1838)
3. All animals have cells (Schwann, 1838)
4. Cells come from other cells (Rudolf Virchow, 1858)