PROFESSOR TYNDALUS RECENT RESEARCHES. 693 



with mould. Here, surely, we have a case of spontaneous generation. 

 Let us look to its history. 



After the air has been expelled from a boiling liquid, it is diflScult 

 to continue the ebullition without " bumping." The liquid remains 

 still for intervals, and then rises with sudden energy. It did so in the 

 case now under consideration ; and one of the tubes boiled over, the 

 liquid overspreading the resinous surface in which the bell-jar was im- 

 bedded. For three weeks the infusions had remained perfectly clear. 

 At the end of this time, with a view of renewing the air of the bell-jar, 

 it was exhausted, and refilled by fresh air which had passed through a 

 plug of cotton-wool. As the air entered, attention was attracted by 

 two small spots of penicillium resting on the liquid which had boiled 

 over. It was at once remarked 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 containing the hay-infusion. It has 

 by this time grown so as to fill a large portion of the tube. For nearly 

 a month longer, the two tubes containing the turnip and mutton infu- 

 sions maintained their transparency unimpaired. Late in December, 

 the mutton-infusion, which was in dangerous proximity to the outer 

 mould, showed a tuft upon its surface. The beef-infusion continued 

 bright and clear for nearly a fortnight longer. The recent cold 

 weather caused me to add a third gas-stove to the two which had 

 previously warmed the room in which the experiments are conducted. 

 The warmth of this stove played upon one side of the bell-jar, causing 

 currents ; and, on the day after the lighting of the stove, the beef-in- 

 fusion 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 genera- 

 tion " far more striking than many that have been adduced. 



In further illustration of the dangers incurred in this field of in- 

 quiry, the excellent paper of Dr. Roberts on " Biogenesis," in the 

 Philosophical Transactions for 1874, is referred to. Dr. Roberts fills 

 the bulb of an ordinary pipette up to about two-thirds of its capacity 

 with the infusion to be examined. In the neck of the pipette he 

 places a plug of dry cotton-wool. He then hermetically seals the 

 neck, and dips the bulb into boiling water or hot oil, where he permits 

 it to remain the requisite time. Here we have no disturbance from 

 ebullition, and no loss by evaporation. The bulb is removed from the 

 hot water, and permitted to cool. The sealed end of the neck is then 

 filed off, the cotton-wool alone interposing between the infusion and 

 the atmosphere. 



The arrangement is beautiful, but it has one weak point. Cotton- 

 wool free from germs is not to be found, and the plug employed by 



