PUTEEFACTION 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 Penidllium and diffuse 

 them in the bellyjar. 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 fiU. 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 Penicillvum upon its sm-face. 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 PenicUlium 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,' resembUng a huge 

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

 pumped out several times, air filtered carefully through 



