658 WHO ARE SOME OF THE MAKERS OF BIOLOGY? 



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by simple experiments that flies laid their eggs in decaying meat, 

 which accounted for the maggots found there. But the con- 

 troversy frequently raged between those who believed that life 

 arose spontaneously and those who believed that all life came from 



previous life. It 

 was believed that 

 bacteria arose spon- 

 taneously in water, 

 even as late as 1876, 



or no*. when Professor 

 Tyndall proved by 

 experiment the con- 

 trary to be true. 



Physiology. In 

 1651 William 

 Harvey, physician 

 of Charles I of 

 England, showed 

 that living things 

 came from egg cells. 

 It was much later, 

 however, that the 

 part played by the 

 sperm in fertilizing the egg cell was carefully worked out. It is to 

 Harvey, too, that we owe the discovery of the circulation of the 

 blood. He showed that blood moves in a complete circuit in the 

 body and that the heart pumps it. Up to his time the arteries 

 had been thought to be air tubes, because after death they were, 

 empty of blood. Harvey might be called the father of modern 

 physiology as well as of embryology. The heading of this unit 

 shows an old print of Harvey demonstrating the circulation of 

 blood to a group of scientists. 



Van Leeuwenhoek, who lived from 1632 to 1725, is known as the 

 maker of the improved microscope, although his simple lenses 

 were far from equaling our modern instruments. We also connect 

 his name with the confirmation of Harvey's work on the circulation 

 of the blood, for it was he who first saw the circulation of blood in 



Tyndall used this apparatus to help disprove the theory that 

 bacteria arose spontaneously. He put natritive fluids in the cul- 

 ture tubes which were enclosed in a box containing air. The 

 sides of the box were sticky so that all dust particles in air were 

 held. A beam of light was used to see if any free particles were 

 floating in the air. The tubes were heated. No organisms ap- 

 peared in the tubes, as long as they were kept in the dust-free air. 



