ROOMS FOR SURGICAL OPERATIONS. 183 



and the bellows worked, a current of air passes through 

 the layer of cotton wool and two pieces of cloth on the 

 mouth of the funnel, then through the end of the room (E) 

 (which also acts as a filter), and, moving bodily along the 

 room, escapes at the window, little or no special currents or 

 draughts being apparently produced. This I observed by 

 previously filling the room with fumes. The force of the 

 air, by passing through the two layers of cotton wool, was 

 evidently equally distributed throughout the whole space of 

 the room. My first experiment with this arrangement was 

 made by simply working the bellows for about twenty 

 minutes to endeavour to drive the impure air with its float- 

 ing particles and spores out of the room by passing into it 

 the filtered air from the bellows, then boiling one half of 

 some flour paste in a basin inside the room for a minute 

 or two, and, lastly, closing the window with the glass, the 

 other half of the paste being boiled in a similar basin and 

 left outside exposed to the ordinary or contaminated air. 

 After a few days the difierence between the two pastes was 

 very marked ; the surface of the one left outside the room 

 was completely covered with fungus, whereas only four or 

 five little specks of fungus were observed to be growing on 

 the surface of the one inside the house, which soon developed 

 into four or five little buttons of fungus. I considered that 

 the spores which had fallen on this flour paste must have 

 been sticking to the sides and roof of the room ; and to eli- 

 minate this assumed cause of error I drew out the supporting 

 rods of the room, crushed it up and boiled it in water for 

 half an hour, then allowed it to dry, and repeated the same 

 experiments with the two basins of flour paste, the bellows 

 being first worked, and the glass then taken out and laid 

 down in the ordinary or contaminated air, then wiped with 

 a clean cloth and replaced. In a few days afterwards the 

 paste outside the house was completely covered with fungi, 



