SPONTANEOUS GENERATION. 393 



strengthened by the microscope. With reference to 

 their origin these organisms were called 'Infusoria/ 

 Stagnant pools were found full of them, and the obvi- 

 ous difficulty of assigning a germinal origin to exist- 

 ences so minute furnished the precise condition neces- 

 sary to give new play to the notion of heterogenesis 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 his ' organic 

 molecules,' and the latter assuming the existence of a 

 special 'vegetative force' which drew the molecules 

 together so as to form living things. On the other side, 

 we have the celebrated Abbe Lazzaro Spallanzani, who 

 in 1777 published results counter to those announced 

 by Needham in 1748, and obtained by methods so pre- 

 cise 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 ob- 

 durate infusorial germs, for otherwise the process he 

 followed would, as was long afterwards proved by Wy- 

 man, have infallibly yielded life. But his refutation 

 of the doctrine of spontaneous generation is not the 

 less valid on this account. Nor is it in any way upset 



