SPONTANEOUS GENERATION iii 



criticism in the scientific world ; but, as usual, Pasteur 

 was in the right. From the conditions under which 

 they grow he suggested the name 'anaerobic' for 

 such bacteria as B. butyricus ; and later observers 

 have shown that many pathogenic micro-organisms 

 are anaerobic. At the present day bacilli are usually 

 divided into two groups, those which grow in the 

 presence of free oxygen (aerobic), and those which will 

 not grow in the presence of oxygen (anaerobic). 



Naturally the question of spontaneous generation 

 occupied much of Pasteur's time. The view, that in 

 certain circumstances living matter originates from 

 non-living, lasted from the classical times until towards 

 the end of the last century. The size of the animal 

 so produced varied, however, inversely with the 

 growth of our era. Van Helmont in the seventeenth 

 century had a recipe for producing mice. Place a 

 piece of linen somewhat soiled in a vessel, add some 

 grains of corn, flavour with a piece of cheese, and in 

 twenty-one days the mice will be there, fully adult 

 and of both sexes. 



About the time that van Helmont died there was 

 coming to the front in Florence a young Italian poet, 

 born at Arezzo — in whose cathedral he now lies 

 buried — who had a singular turn for investigating the 

 secret workings of organic nature. Francesco Redi 

 — his name is immortalized in the little larva Redia — 

 was courtier, poet, doctor, above all zoologist; and 

 he belonged to that comparatively small section of 

 teetotallers who have enthusiastically sung the merits 

 of wine.* By a series of accurate experiments, such 



* A volume of Redi's poems, entitled ' Bacco in Toscano,' 

 was published in 1804. Longfellow says of him : 



' Even Redi, when he chanted 

 Bacchus in the Tuscan valleys, 

 Never drank the wine he vaunted 

 In his dithyrambic sallies.' 



