ORIGIN OF LIFE 219 



will find the fields swarming with mice begot of the mud of the 

 Nile, to the great calamity of the inhabitants." 



Naturally, with the gradual increase in knowledge of the com- 

 plexity of organisms, the idea of abiogenesis, or spontaneous 

 generation, was restricted more and more to the lower forms. It 

 remained, however, for Francisco Redi during the latter part of the 

 seventeenth century to question seriously the general proposition, 

 and to substitute direct experimentation for discussion and hear- 

 say. By the simple expedient — it seems simple to-day — of pro- 

 tecting decaying meat from contamination by flies, he demon- 

 strated that these insects are not developed from the flesh and 

 that the apparent transformation of meat into maggots is due 

 solely to the development of the eggs deposited thereon by flies. 



One may imagine that the practical man of affairs scoffed at 

 Redi toiling under the Italian sun with meat and maggots to satisfy 

 a scientific curiosity, and little dreamed that the practical results 

 which germinated from this 'folly' would be among the most 

 important factors in twentieth-century civilization. Indeed, it is 

 difficult to overestimate the importance of Redi's conclusion from 

 either the theoretical or practical viewpoint, for with it was def- 

 initely formulated the theory that matter does not assume the 

 living state, at the present time at least, except from preexisting 

 living matter. 



The influence of this work gradually became evident in schol- 

 arly literature. One author during the next century states that 

 "spontaneous generation is a doctrine so generally exploded that 

 I shall not undertake to explode it. It is so evident that all animals, 

 yea and vegetables, too, owe their production to parent animals and 

 vegetables, that I have often admired the sloth and prejudices of 

 ancient philosophers in taking it upon trust." Another writes 

 that he "would as soon say that rocks and woods engender stags 

 and elephants as affirm that a piece of cheese generates mites." 



But it is not to be supposed that the time-honored doctrine of 

 spontaneous generation actually had been so easily relegated to 

 the myths of the past, Redi's work and these eighteenth-century 

 opinions to the contrary. Indeed, the history of the establishment 

 of biogenesis — all life from life — extends down almost to the 

 present time, for no sooner had experiment apparently disposed of 

 spontaneous generation than it arose again with fresh vigor in a 

 slightly different form demanding further investigation. 



