DEATH AND RESURRECTION. 57 



With the discovery of the microscopi- 

 cal organic world, a new field and one 

 more difficult of access was opened for 

 research. It was now the sudden and 

 unexpected appearance of bacteria, as- 

 pergillus and infusoria in places where 

 their previous existence could not be 

 imagined, that maintained the belief in 

 generatio spontanea. But by and by we 

 learned to understand the propaga- 

 tion and life also of these low 

 organisms, their ability to withstand 

 very high or very low temperatures, 

 and the facility with which they 

 are spread by the air and, above all, 

 their rapid propagation. It commenced 

 to be more and more evident that even 

 in the micro-organic world no parent- 

 less generation exists. The investiga- 

 tions by Spallanzani, and later by 

 Schultze, Schwann, von Dusch and 

 Schroder, were epochal for the estab- 

 lishing of this fact. Their method, how- 

 ever, left some room for criticism 

 which was forcefully pointed out by a 



