SPONTANEOUS GENERATION 87 



that did not appear to be unreasonable. It was 

 observed that they made their appearance in infu- 

 sions previously boiled, and exposed to the air. As 

 boiling was held to kill all living matter, it was 

 inferred that the organisms appearing in boiled 

 infusions must have arisen by spontaneous genera- 

 tion. Moreover, these minute organisms seemed so 

 very different from higher forms of life, and as 

 very little was known of their life history, their 

 spontaneous origin was all the more readily ac- 

 cepted. The Irish priest, Needham, had heated 

 flasks of organic infusions, corked them up while 

 hot, and found, in the course of a few days, that 

 the liquid became turbid from the multitude of 

 minute organisms which were engendered within it. 

 The origin of these living forms was attributed to 

 a "vegetative force" operating on the organic sub- 

 stances of the infusion. 



These experiments aroused the interest of an- 

 other priest, the sagacious Abbe Spallanzani, who 

 attacked the subject by somewhat more rigorous 

 methods. He made infusions in flasks whose con- 

 tents were thoroughly boiled. Being suspicious of 

 corks, he sealed his flasks by drawing out their 

 necks and fusing them, thus absolutely excluding 

 all air, and hence any germs which might be car- 



