20 THEORIES OF SPONTANEOUS GENERATION 



of Louis Joblot.^^ This distinguished follower of van Leeu- 

 wenhoek used infusions of hay which were swarming wdth 

 micro-organisms, boiled them for 15 minutes and then poured 

 equal parts into two vessels. One of these he covered closely 

 w4th parchment before it cooled, the other was allow^ed to 

 stand uncovered. In the open vessel very small living things 

 (apparently infusoria) grew abundantly, but they did not 

 appear in the closed one. At the end of the experiment the 

 parchment was removed from the closed vessel too, after 

 w^hich the infusion was soon populated with micro-organisms. 

 However, the experiments of Joblot were not convincing 

 enough for his contemporaries and were later completely 

 forgotten. 



Philosophical thought at that time could still not renounce 

 the principle of spontaneous generation and, as before, the 

 dispute betw^een the different schools was concerned not 

 with whether or not microbes can develop of their own 

 accord, but only with the spiritual or material basis of this 

 apparently self-evident ' phenomenon '.'"' 



The discovery of the extremely small germs of life which 

 were to be found everywhere was expressed in the philo- 

 sophical system of G. Leibnitz (1646-1716). His teachings 

 about monads included metaphysical rehashing of the con- 

 temporary data of mathematics and science. According to 

 Leibnitz the monads are primary centres of spiritual force. 

 As the ultimate sources of everything they must be character- 

 ised by absolute simplicity and individuality. Matter being 

 inherently passive, the monads constitute the spiritual sub- 

 stance, for only the spirit, in Leibnitz's view, has the capacity 

 for uninterrupted activity.^* 



Starting from these assumptions, Leibnitz considered that 

 life cannot be explained simply on the basis of bodily forces. 

 In particular, he considered the possibility that higher plants 

 and animals could arise by spontaneous generation from 

 decaying material as disproved by direct experiment. The 

 development and disappearance of living things is but the 

 evolution and involution of eternally existing germs. Those 

 substances which we usually consider inorganic contain 

 within themselves a whole world of germs of life. " Even in 

 vinegar and bookbinder's paste," wrote Leibnitz, " these 



