478 THE POPULAR SCIENCE MONTHLY. 



small to permit the eggs to fall through, no maggots were generated 

 in the meat. They were, on the contrary, hatched upon the gauze. 

 By a series of such experiments Redi destroyed the belief in the 

 spontaneous generation of maggots in meat, and with it doubtless 

 many related beliefs. The combat was continued by Vallisneri, 

 Schwammerdam, and Reaumur, who succeeded in banishing the notion 

 of spontaneous generation from the scientific minds of their day. In- 

 deed, as regards such complex organisms as those which formed the 

 subject of their researches, the notion was banished forever. 



But the discovery and improvement of the microscope, though 

 giving a death-blow to much that had been previously written and 

 believed regarding spontaneous generation, brought also into view a 

 world of life formed of individuals so minute so close as it seemed 

 to the ultimate particles of matter as to suggest an easy passage 

 from atoms to organisms. Animal and vegetable infusions exposed 

 to the air were found clouded and crowded with creatures far beyond 

 the reach of unaided vision, but perfectly visible to an eye strengthened 

 by the microscope. With reference to their origin these organisms 

 were called "infusoria." Stagnant pools were found full of them, and 

 the obvious difficulty of assigning a germinal origin to existences so 

 minute furnished the precise condition necessary to give new play to 

 the notion of heterogenesis or spontaneous generation. 



The scientific world was soon divided into two hostile camps, the 

 leaders of which alone can here be briefly alluded to. On the one 

 side we have Buffon and Needham,the former postulating his "organic 

 molecules," and the latter assuming the existence of a special "vege- 

 tative force" which drew the molecules together so as to form living 

 things. On the other side we have the celebraled Abbe Lazzaro 

 Snallanzani, who in 1877 published results counter to those announced 

 by Needham in 1748, and obtained by methods so precise as to com- 

 pletely overthrow the convictions based upon the labors of his prede- 

 cessor. Charging his flasks with organic infusions, he sealed their 

 necks with the blow-pipe, subjected them in this condition to the heat 

 of boiling water, and subsequently exposed them to temperatures 

 favorable to the development of life. The infusions continued un- 

 changed for months, and when the flasks were subsequently opened 

 no trace of life was found. 



Here I may forestall matters so far as to say that the success of 

 Spallanzani's experiments depended wholly on the locality in which 

 he worked. The air around him must have been free from the more 

 obdurate infusorial germs, for otherwise the process he followed 

 would, as was long afterward proved by Wyman, have infallibly 

 yielded life. But his refutation of the doctrine of spontaneous gen- 

 eration is not the less valid on this account. Nor is it in any way 

 upset by the fact that others in repeating his experiments obtained 

 life when he obtained none. Rather is the refutation strengthened by 



