THE ORIGIN OF LIFE 9 



must have developed spontaneously in the liquids. He had 

 plenty of followers in this conclusion ; for the idea was quite 

 in accord with the views of the day. 



Meanwhile another school of scientists, led by Spallanzani, 

 vigorously opposed Needham and his school. They claimed 

 that if sufi&cient pains were taken to kill all the microorgan- 

 isms, none would develop, and they carried on experiments 

 to prove their point. The dispute continued unsettled until 

 about the middle of the nineteenth century. On one side 

 it was claimed that those who obtained evidence of micro- 

 scopic hfe in boiled infusions did not carry on the experiments 

 carefully enough ; on the other side it was claimed that heat 

 changed the nature of the liquids so that microorganisms 

 could no longer develop imtil air was admitted. It seems 

 strange, indeed, that anything so obvious to us to-day should 

 have been imder dispute among eminent scientists for so 

 many years. 



Oddly enough, the question was settled in a practical way 

 while this dispute was still raging. Early in the nineteenth 

 century (1809) a Frenchman, Appert, discovered that if 

 perishable food was placed in proper containers, sufficiently 

 heated and afterwards hermetically sealed, it would keep 

 without spoiling. Appert was, in fact, the founder of the 

 canning industry. Now it was realized even in those days 

 that the spoilage of food and the development of micro- 

 scopic organisms in it went hand in hand ; and if any scientist 

 had stopped to think about it, he would have realized that 

 Appert was successfully keeping living things out of his jars 

 of preserved food. That this can be done is immensely im- 

 portant to any housekeeper; and it plainly could not be 

 done if microscopic life could originate spontaneously in any 



