1876.] Phenomena of Putrefaction and Infection. 177 



clear exception to what had previously appeared to be a general law. 

 The cause of his perplexity was finally traced to the tiniest speck of an 

 infusion containing Bacteria, which had clung by capillary attraction to 

 the point of one of his pipettes. 



Again, three tubes containing infusions of turnip, hay, and mutton 

 were boiled, on the 2nd of November, under a bell-jar containing air so 

 carefully filtered that the most searching examination by a concentrated 

 beam failed to reveal a particle of floating matter. At the present time 

 every one of the tubes is thick with mycelium and covered 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 difficult 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 over- 

 spreading the resinous surface in which the bell-jar was imbedded. For 

 three weeks the infusions had remained perfectly clear. At the end of 

 this time, with a view of renewing the air of the jar, it was exhausted, 

 and refilled by fresh air which had passed through a plug of cotton-wool. 

 As the air entered, two small spots of Penicillium, resting on the 

 liquid which had boiled over, attracted attention. 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 f B 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-infusions maintained their trans- 

 parency 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 the author to add a third 

 gas-stove to the two which had previously warmed the room in which the 

 experiments are conducted. The warmth played upon one side of the 

 bell-jar, causing currents within it ; and 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 three cases of 

 "spontaneous generation" far more striking than many that have been 

 adduced. 



In further illustration of the danger incurred in this field of inquiry, 

 the author refers to the excellent paper of Dr. Roberts on Biogenesis, in 

 the Philosophical Transactions for 1874. Dr. Eoberts fills the bulb of 



o2 



