PUTItEFACTION AND INFECTION. 



89 



Fig. 5. 



the ends of two upright copper wires, which pass 



through the stand and are seen coiled outside it. The 



shade is surrounded below by a tin collar, with a space of 



about half an inch all round between it and the shade. 



This space is filled with cotton-wool firmly packed. 



Connecting the wires with a battery of fifteen cells, the 



spiral p was raised to whiteness, and was permitted to 



continue so for five minutes. Experiments previously 



executed had shown that 



this sufficed for the entire 



removal of the floating 



matter. When the spiral 



was heated, a portion of 



the expanded air was driven 



through the cotton - wool 



packing below ; and when 



the current was interrupted, 



this air, returning into the 



shade, was prevented by the 



cotton-wool from carrying 



any floating matter with 



it. 



The first thi'ee substances 

 brought into contact with 

 air calcined in this way were damson-juice, pear-juice, 

 and infusion of yeast. They were boiled for five min- 

 utes, and for five months they have remained without 

 speck or turbidity. Other tubes similarly boiled, and 

 placed underneath shades containing the floating matter 

 of the air, have long since fallen into mould and rotten- 

 ness. 



Turnip- and hay-infusions, rendered slightly alkaline, 

 have been mentioned as particularly prone to spon- 

 taneous generation. I wished to test this. On the 

 26th of November, therefore, four shades were prepared, 



