INTRODUCTION. 19 



About 1668, Francesco Redi seems to have been the 

 first to doubt that the maggots familiar in putrid meat 

 arose de novo : "Watching meat in its passage from 

 freshness to decay, prior to the appearance of maggots, 

 he invariably observed flies buzzing around the meat and 

 frequently alighting on it. The maggots, he thought, 

 might be the half-developed progeny of these flies. 

 Placing fresh meat in a jar covered with paper, he found 

 that although the meat putrefied in the ordinary way, 

 it never bred maggots, while meat in open jars soon 

 swarmed with these organisms. For the paper he sub- 

 stituted fine wire gauze, through which the odor of. the 

 meat could rise. Over it the flies buzzed, and on it they 

 laid their eggs, but the meshes being too small to per- 

 mit the eggs to fall through, no maggots generated in 

 the meat; they were, on the contrary, hatched on the 

 gauze. By a series of such experiments Redi destroyed 

 the belief in the spontaneous generation of maggots in 

 meat, and with it many related beliefs." 



It was not long before Leeuwenhoek, Vallismeri, 

 Swammerdan, and others, following the trend of Redi's 

 work, contributed additional facts in favor of his view, 

 and it may safely be asserted that ever since the time 

 of this eminent man the tide of scientific opinion has 

 turned more and more strongly against the idea that 

 life is spontaneously generated. 



About this time (1675) one whose name has been 

 already mentioned, Anthony van Leeuwenhoek, and who 

 is justly called the "Father of microscopy," came into 

 prominence. An optician by trade, Leeuwenhoek devoted 

 much time to the perfection of the compound micro- 

 scope, which was just coming into use. The science of 

 optics, however, was not sufficiently developed to enable 

 him to overcome the errors of refraction, and after the 

 loss of much time he turned to the simple lens, using it 

 in so careful and remarkable a manner as to be able 

 to record his observations in one hundred and twelve 

 contributions to the Philosophical Transactions. Leeu- 



