PUTREFACTION AND INFECTION. 87 



was directed to a couple of small round patches of Peni~ 

 cillium resting in the liquid that had boiled over on the 

 resin. I at once made the remark that the experiment 

 was a dangerous one, as the entering air would probably 

 detach some of the spores of the Penicillium and diffuse 

 them in the bell-jar. This was, therefore, filled very 

 slowly, so as to render the disturbance a minimum. 

 Next day, however, a tuft of mycelium was observed at 

 the bottom of one of the three tubes, namely that con- 

 taining the hay-infusion. It soon grew large enough 

 to fill a considerable portion of the tube. For nearly a 

 month longer the two tubes containing the turnip- and 

 mutton-infusions maintained their transparency unim- 

 paired. Late in December the mutton -infusion, which 

 was in dangerous proximity to the outer mould, showed 

 a tuft of Penicillium upon its surface. The beef- 

 infusion continued bright and clear for nearly a fort- 

 night longer. The cold winter weather caused me to 

 add a third gas-stove to the two which had previously 

 warmed the room where the experiments are conducted. 

 The warmth of this stove played upon one side of the 

 bell-jar ; and on the day after the lighting of the stove, 

 the beef-infusion gave birth to a tuft of mycelium. 

 In this case the small spots of Penicillium might have 

 readily escaped attention ; and had they done so we 

 should have had here three cases of ' spontaneous gen- 

 eration ' more striking than most of those that have 

 been adduced in support of this doctrine. 



The experiment was subsequently made upon a 

 larger scale. Twelve very large test-tubes were caused 

 to pass air-tight through a slab of wood ; the wood was 

 thickly coated with cement, in which, while it was hot 

 and soft, a heated ' propagating glass,' resembling a huge 

 bell-jar, was imbedded. The air within the glass was 

 pumped out several times, air filtered carefully through 



