The TTL output stage is a rather complicated pushâpull circuit known as a totem-pole output (the transistors, diode, and resistor in the right-most slice of this TTL logic gate circuit). It sinks currents better than it sources current.
The theory for spontaneous generation refers to the idea that life can produced from nonliving things. Lazzaro Spallanzani proposed in his experiement that air was necessary for spontaneous generation.
Many people said that all that Spallanzani did was prove that Spontaneous Generation did not occur when there was no air. The image on the top shows how John Needham conducted his experiment. Because the flask was not sealed, microorganisms were still able to get in after the water cooled down.