100 Dr. Tyndall. Germinal Matter of the Air. [Feb. 14, 



Reflecting on this experiment, and knowing that a sealed chamber, 

 simply wetted within, suffices to detain the floating matter coming 

 into contact with its interior surface, I thought that the same must 

 hold good for the air-bubbles passing through a group of Liebig's 

 bulbs. Every bubble, in fact, represents a closed chamber of infini- 

 tesimal size, and it seemed plain that if the walls of this chamber were 

 formed of water instead of sulphuric acid, the floating matter would 

 be effectually intercepted. This was a conclusion arrived at last 

 summer, in the Alps. On my return to London I tested the con- 

 clusion, and found it verified by experiment. 



Two large test-tubes, each about two-thirds filled with turnip in- 

 fusion, were so connected together, that air could be drawn through 

 them in succession. With a view to their sterilization, the tubes were 

 subjected for a sufficient time to the action of boiling water, and 

 permitted to remain afterwards in a room kept at a temperature of 

 90° Fahr., until it was evident that sterilization had been complete. 

 Two narrow tubes, passed through the cork of each test-tube, in the same 

 manner as in Schulze's flask, and it was so arranged that the tube which 

 delivered the air should end near the surface of the liquid, the exit 

 tube in each case ending immediately under the cork. Two series of 

 Liebig's bulbs, charged with pure water, were attached to the two 

 ends of this arrangement; one series being connected with a large 

 receiver, placed on the plate of an air-pump, and the other left open 

 to the air. The connection between the receiver and the adjacent 

 series of bulbs being first cut off by a pinch-cock, the receiver was 

 exhausted, and, by carefully loosening the pinch-cock, a very slow 

 passage of the air through the test-tubes was secured. The rate of 

 transfer was, however, such, that the air above the infusions was re- 

 newed twenty or thirty times in twenty-four hours. At the end 

 of twelve days, during which this process was continued day and night, 

 the turnip juice was perfectly pellucid and free from life. Two days' 

 exposure to ordinary air sufficed to render the infusion muddy. 



After twelve days the pinch- cock was opened, so as to allow a 

 momentary inrush of the external air, which was immediately checked 

 by the reclosing of the cock. Three days afterwards, the infusion of 

 the test-tube, into which the air first entered, was muddy and crowded 

 with life. The contamination did not reach the second test-tube, 

 which remains to the present hour intact. Other experiments of a 

 similar character have been executed with precisely the same result. 

 I will not occupy the Society's time by describing them. Suffice it to 

 say, that they completely verify the conclusion that, in Schulze's ex- 

 periment, water may be substituted for sulphuric acid and caustic 

 potash without any alteration in the result. 



