222 CRITIQUES AND ADDRESSES. [x. 



expose them to the air in hot weather, and in a few days 

 they swarm with maggots. You tell me that these are 

 generated in the dead flesh ; but if I put similar bodies, 

 while quite fresh, into a jar, and tie some fine gauze over 

 the top of the jar, not a maggot makes its appearance, 

 while the dead substances, nevertheless, putrefy just in 

 the same way as before. It is obvious, therefore, that the 

 maggots are not generated by the corruption of the meat ; 

 and that the cause of their formation must be a something 

 which is kept away by gauze. But gauze will not keep 

 away aeriform bodies, or fluids. This something must, 

 therefore, exist in the form of solid particles too big to 

 get through the gauze. Nor is one long left in doubt what 

 these solid particles are ; for the blow-flies, attracted by 

 the odour of the meat, swarm round the vessel, and, urged 

 by a powerful but in this case misleading instinct, lay eggs 

 out of which maggots are immediately hatched upon the 

 gauze. The conclusion, therefore, is unavoidable ; the 

 maggots are not generated by the meat, but the eggs which 

 give rise to them are brought through the air by the flies. 

 These experiments seem almost childishly simple, and 

 one wonders how it was that no one ever thought of 

 them before. Simple as they are, however, they are 

 worthy of the most careful study, for every piece of 

 experimental work since done, in regard to this subject, 

 has been shaped upon the model furnished by the Italian 

 philosopher. As the results of his experiments were the 

 same, however varied the nature of the materials he 

 used, it is not wonderful that there arose in Kedi's mind 

 a presumption, that, in all such cases of the seeming pro- 

 duction of life from dead matter, the real explanation 

 was the introduction of living germs from without into 

 that dead matter. 1 And thus the hypothesis that living 



1 " Pure contentandomi sempre in questa ed in ciascuna altro cosa, da cias- 

 cuno piii savio, la dove io difettuosamente parlassi, esser corretto ; non tacero, 



