PUTEEFACTION AND INFECTION. 85 



for example, that a mineral solution does not develop 

 Bacteria when exposed to the air; and he concludes 

 from tjais that an organic infusion also may be thus ex- 

 posed without danger of infection. He exposes turnip- 

 juice accordingly, obtains a crop of Bacteria, which, in 

 the light of his assumption, are spontaneously generated. 

 Such are the warp and woof of some of the weightiest 

 arguments on this question which have been addressed 

 by him to the Eoyal Society.^ 



Grranting, then, all that Dr. Bastian alleges regard- 

 ing his experiments to be correct, the logical inference 

 would be very different from his inference. In a future 

 essay his position will be more clearly defined. To the 

 examination of his experiments I now address myself. 



§ 18. Experiments with Filtered Air. 



A bell-jar containing about 700 cubic inches of air 

 was firmly cemented to a slab of wood coated ^vith resin, 

 and supported on three legs.^ Through the slab passed, 

 air-tight, three large test-tubes (a, b, c, fig. 4). Prior 

 to cementing, the tubes had been three-fourths filled, 

 one with an infusion of hay, another with an infusion of 

 turnip, and a third with an infusion of mutton. On 

 the 2nd of November the mote-laden air was pumped 

 out, air slowly filtered through a long tight plug of 

 cotton-wool being allowed to take its place. The jar 

 was emptied and refilled until the closest scrutiny by a 

 concentrated beam revealed no floating matter within 

 it. The infusions were then boiled for five minutes, 



' Proceedings, vol. xxi. p. 130. 



2 Xwo hoops of sheet iron, with an annular space about an 

 inch wide, were fastened on to the slab of wood. The annular 

 space was filled with hot cement, into which the hot bell- jar was 

 pressed. The circular space within the smaller hoop was also 

 covered by a layer of cement. 



