ORIGIN OF LIFE 245 



The mouths of the test tubes were freely exposed to the air in 

 the box. The fluids remained free from microorganisms for an 

 indefinite period of time. Later, in order to check his results 

 and to demonstrate that the fluids contained nutritive value, he 

 removed them from the box and exposed them to the outside air. 

 Microorganisms appeared. The importance of this work and the 

 work of Pasteur was far reaching. Keeping dust out was the 

 basis for the sterilization of wounds and surgical instruments, 

 which later led to antiseptic surgery. It was, also, the basis of 

 canning by heating. 



Origin of life. If life comes from life, where did the original 

 life come from? Science has been unable to solve this riddle. 

 One theory, popularly accepted by some scientists, is that when 

 the earth cooled down, there were unusual conditions that made 

 possible the combining of certain elements in the right proportion 

 to form the simplest one-celled plants. From these plants, gradu- 

 ally the entire plant and animal kingdoms have originated. There 

 are no means of knowing whether this actually took place or not. 

 The origin of living matter still remains unsolved by scientists. 



QUESTIONS AND SUGGESTIONS 



1. State the ancient idea of the origin of life. What evidence have 

 you for thinking that some people still have this idea about some forms 

 of life? 



2. Describe the first experiment that was made to prove the theory 

 of spontaneous generation. 



3. Discuss the importance played by the microscope in the con- 

 troversy. 



4. Discuss the experiments of Needham and Spallanzani. 



5. Of what value to scientists of this time was the discovery of 

 oxygen ? 



6. Discuss the controversy of Pouchet and Pasteur. 



7. How do present-day scientists explain the origin of life ? 



