LIFE COMES FROM LIFE 657 



with the improvement of man's condition by the application of 

 certain scientific discoveries. The first group is necessary in 

 order that the second group may work further on the results. 

 It was necessary for men like Charles Darwin and Gregor Mendel 

 to formulate their theories before Luther Burbank or any of the 

 men now working in the Department of Agriculture could benefit 

 mankind by producing new varieties of plants. The discovery of 

 scientific truths must be made before the men of modern medicine 

 can apply them to the cure or prevention of disease. Since we 

 are most interested in discoveries which touch directly upon 

 human life, the men of whom this chapter treats will be those 

 who, directly or indirectly, have benefited mankind. 



PROBLEM I. WHO WERE SOME EARLY WORKERS IN BIOLOGY? 



The discoverers of living matter. The names of a number of 

 men living at different periods are associated with our first knowl- 

 edge of cells. About the middle of the seventeenth century micro- 

 scopes came into use. In 1667, an Englishman named Robert 

 Hooke sliced a piece of cork with a razor and looked at it through 

 a lens. He saw that the cork was made up of many tiny boxes 

 or cells. But he saw only the dead cell walls and not the more 

 important living matter. It was not until 1838 that two German 

 friends, Schleiden (shll'den) and Schwann (shvan), working on 

 plants and animals, discovered that both of these forms of life 

 are built up of units called cells and that these cells were composed 

 of living material. Other biologists gave the name protoplasm to 

 all living matter, and a little later Professor Huxley, a famous 

 Englishman, friend and champion of Charles Darwin, called 

 attention to the physical and chemical qualities of protoplasm so 

 that it came to be known as the chemical and physical basis of life. 



Life comes from life. Another group of men, after years of 

 patient experimentation, proved the fact that life comes from life. 

 In ancient times it was thought that life arose spontaneously; 

 for example, that fish or frogs grew out of the mud of the river 

 bottoms, and that insects came from dew or the rotting of meat. 

 Redi (ra'de), an Italian physician, 1629-1694, was the first to show 



