14 THE GROWTH OF SCIENCE 



made and conclusions drawn. This is the modern scientific method ; 

 science based on experimentation and observation. 



Consider the work of Paul Ehrlich. He wanted to find a 

 chemical that had a deadly effect on certain microbes. First, he 

 studied these particular disease germs by staining them different 

 colors. Then he tried the effect of various chemicals on them. 

 With great patience he persevered, rejecting those tests that were 

 not satisfactory. Finally, his six hundred and sixth experiment 

 was successful. He had found a substance which would kill the 

 germ but would not injure healthy body tissue. 



Dr. Thomas H. Morgan of the Institute of Technology, Pasa- 

 dena, California, has examined the sizes and observed the various 

 body differences of tens of thousands of tiny flies. One of the 

 differences noted was a specimen with colorless instead of pink 

 eyes. He has bred this and other different types through countless 

 o'enerations in his 'efforts to understand heredity. There is no 

 wild jumping to conclusions in his work. It is based on definite, 

 experimental evidence. 



Think of the late Luther Burbank. Acres of ground were tilled, 

 planted, cultivated, and the plants were closely observed by this 

 experimenter. All but one or two plants grown were discarded in 

 his search for specimens of the plant he wanted to breed. He, 

 like other scientists, examined a wealth of data and then made a 

 careful selection from this material. 



Contrast the cabbage juice treatment of typhus fever mentioned 

 before with the scientific investigation of malaria. It was first 

 observed that people living near swamps contracted a fever ; there- 

 fore, it was thought that swampy air caused this malady. The 

 disease was called malaria, meaning bad air. People were cau- 

 tioned to close their windows, particularly at night, to keep out the 

 bad air. Then, beginning with observations based on experimenta- 

 tion, doctors experimented with swampy air to see whether it would 

 give malaria or not. They found that it had no direct relation to 



