280 THE FLOATING-MATTER OF THE AIR. 



strengthened by the microscope. With reference to 

 their origin these organisms were called ' Infusoria.' 

 Stagnant pools were found full of them, and the 

 obvious difficulty of assigning a germinal origin to 

 existences so minute furnished the precise condition 

 necessary to give new play to the notion of hetero- 

 genesis or spontaneous generation. 



The scientific world was soon divided into two hos- 

 tile camps, the leaders of which only can here be 

 briefly alluded to. On the one side, we have Buffon 

 and Needham, the former postulating liis ^organic 

 molecules,' and the latter assuming the existence of a 

 special ' vegetative force ' which drew the molecules 

 together so as to form living thino-s. On the otheFside, 

 we have the celebrated Abbe Lazzaro Spallanzani, who 

 in 1777 published results counter to those ajmounced 

 by Needham in 1748. They were obtained by methods 

 so precise as to completely overthrow the convictions 

 based upon the labours of his predecessor. Charging his 

 flasks with organic infusions, he sealed their necks with 

 the blowpipe, subjected them in this condition to the 

 heat of boiling water, and subsequently exposed them 

 to temperatures favourable to the development of life. 

 The infusions continued unchanged for months, and 

 when the flasks were subsequently opened no trace of 

 life was found. 



Here I may forestall matters so far as to say that 

 the success of Spallanzani's experiments depended wholly 

 on the locality in which he worked. The air around 

 him must have been free from the more obdurate in- 

 fusorial germs, for otherwise the process he followed 

 would, as was long afterwards proved by Wyman, have 

 infallibly yielded life. But his refutation of the doc:^ 

 trine of spontaneous generation is notthe less valid on 

 this account. Nor is it in any way upset by the fact, 



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