72 WHAT IS LIFE 



eggs of flies deposited thereon, and moreover de- 

 monstrated the fact that if the meat was kept 

 covered with gauze no maggots appeared in it. 

 And as a result of this and of other observations 

 the idea of spontaneous generation was put aside 

 for a time, indeed until the microscope began to 

 reveal the surprising number and variety of small 

 living objects which had previously been hidden 

 from men's eyes. The discussion continued at in- 

 tervals during the eighteenth century and it is 

 curious to note that two of the most active antago- 

 nists were both Catholic priests, Needham (1713- 

 1781) who supported the theory of spontaneous 



Spaiianzani generation, and Spallanzani (1729-1799) who op- 

 posed it. It was Spallanzani who first performed 

 the experiment of boiling infusions for a sufficient 

 time in hermetically sealed vessels, after which 

 treatment, as he showed, no life was developed in 

 them. 



After this demonstration the theory of spon- 

 taneous generation was once more consigned to 

 oblivion, or at least to comparative oblivion, for it 

 always possessed, as it does to this day, certain 

 adherents. 



Pouchet Amongst these the most important was the elder 



Pouchet who in 1858 declared that he had seen the 

 spontaneous production of infusoria in a sterilised 

 fluid which had been exposed only to air also 



