l6 THEORIES OF SPONTANEOUS GENERATION 



generation and even went further and carried out a number 

 of observations and experiments to confirm the hypothesis. 

 For example, he gives a well-known receipt for making mice 

 from gi'ains of wheat. He held that human sweat could serve 

 as the life-giving principle. For this it was necessary to place 

 a dirty chemise in some sort of receptacle which contained 

 wheat grains. After 21 days the ' fermentation ' was stopped 

 and the exhalations from the shirt together with those of 

 the corn had formed living mice. It was especially surprising 

 to van Helmont that these artificially produced mice were 

 exactly like those born from the seed of their parents.^" 



Neither did Harvey (1578-1657), the originator of the 

 theory of the circulation of the blood, reject the idea of spon- 

 taneous generation. However, although the celebrated phrase 

 omne vivum ex ovo (everything alive comes from an egg) 

 belongs to him, he was here giving a very wide meaning to 

 the word egg. He considered generatio aequivoca (spontane- 

 ous generation) of worms, insects, etc., to be perfectly possible 

 as a result of the activity of special forces which develop 

 during putrefaction and similar processes. ^^ 



This also was the view of Harvey's contemporary, the 

 founder of seventeenth century English materialism, Francis 

 Bacon (1561-1626). In his works he expressed the opinion 

 that various plants and animals (such as flies, ants and frogs) 

 could arise spontaneously in the course of the decay of various 

 materials. However, he approached this phenomenon from 

 a materialist position and saw in it only a proof of the absence 

 of an impassable barrier between the inorganic and the 

 organic world. ^^ 



The materialistic interpretation of spontaneous generation 

 was particularly clearly expressed by Descartes (1596-1650).^^ 

 This great French philosopher, although he believed the 

 spontaneous development of living things to be beyond 

 dispute, nevertheless categorically denied that this emergence 

 occurred under the influence of the anima vegetativa of the 

 scholasts, the arche of Paracelsus, the * spirit of life ' of van 

 Helmont or any other spiritual principle. In sharp contra- 

 distinction to the religious teachings then prevailing and to 

 the anthropocentric tendencies of mediaeval natural philos- 



