THE BEGINNINGS OF LIFE 



what beyond their usual meanings to call such 

 speculations " scientific." They were the pro- 

 duct of an almost total absence of such know- 

 ledge as is now called scientific. It was possible 

 to infer that such highly organized creatures as 

 hymenopterous insects, suddenly appearing in 

 putrescent meat, were spontaneously generated 

 there, only because so little was definitely known 

 about the relations of organisms to one another 

 and to the inorganic world. Accordingly, with 

 the very beginnings of modern biological know- 

 ledge, and with the somewhat more cautious and 

 systematic employment of induction character- 

 istic of the seventeenth century, the old belief 

 in spontaneous generation was called in ques- 

 tion. By a series of very simple but apt experi- 

 ments, in which pieces of decaying meat were 

 protected from maggots by a gauze covering, 

 the illustrious Redi proved, to the satisfaction 

 of every one, that the maggots are not produced 

 from the substance of the meat, but from eggs 

 deposited therein by flies. So conclusive were 

 these experiments that the belief in spontaneous 

 generation, which had hitherto rested chiefly 

 upon phenomena of this sort, was almost uni- 

 versally abandoned, and the doctrine that every 

 living thing comes from some living thing — 

 omne vivum ex vivo — received that general ac- 

 ceptance which it was destined to retain down 

 to the present time. With the progress of bio- 



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