36 



became tenanted with an immense number of these 

 micro-organisms. The question arose whether 

 they sprang into existence from the fortuitous 

 concourse of disuniting atoms of the organic matter 

 or whether they were derived by parentage from 

 pre-existing organisms. Spallanzani, who Hved in 

 the eighteenth century, performed the experiment 

 of placing the organic liquid in a vessel, hermetically 

 sealing it, and afterwards exposing it to a tem- 

 perature sufficient to destroy the life of any living 

 matter present, and found that under these circum- 

 stances no organisms became developed. It was 

 suggested that the presence of air might be a 

 necessary condition for the re-arrangement of the 

 elements of the organic substance into living 

 matter, and through this being excluded in 

 Spallanzani's experiment it might be thereby 

 rendered fallacious. Schulze and Schwann came 

 upon the field just about fifty years ago and 

 devised an experiment which stands invested with 

 historical renown. They placed the organic liquid 

 in a flask and boiled it to effect the destruction of 

 any life that might exist. The flask was closed 



